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    Programmable ControllersTheory and ImplementationSecond EditionL.A. BryanE.A. Bryan

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    THEORY AND IMPLEMENTATIONPROGRAMMABLECONTROLLERSAn Industrial Text Company PublicationAtlanta • Georgia • USASecond EditionL. A. BryanE. A. Bryan

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    © 1988, 1997 by Industrial Text CompanyPublished by Industrial Text CompanyAll rights reservedFirst edition 1988. Second edition 1997Printed and bound in the United States of America03 02 01 00 99 98 97 10 9 8 7 6 5 4 3 2| | | | | | | | | | | || | | | | ...

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    iiiContentsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCONTENTS 10,Preface ..................................................................................................... ix 11,About the Authors ..............................................................

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    ivContentsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com 139,5-5 139,Configuring the PLC Memory—I/O 139,Addressing ................................. 127 144,5-6 144,Summary of Memory, Scanning, and I/O Interaction.......................... 132 145,5-7 145,Mem...

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    vContentsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com 324,9-8 324,Counter Instructions ............................................................................. 312 329,9-9 329,Program/Flow Control Instructions ................................................

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    viContentsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com 635,14-3 635,Process Dynamics ................................................................................ 623 644,14-4 644,Laplace Transform Basics .......................................................

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    viiContentsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com 878,18-7 878,Network Protocols ................................................................................ 866 886,18-8 886,Network Testing and Troubleshooting...........................................

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    ixPrefaceIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPREFACESince the first edition of this book in 1988, the capabilities of programmablelogic controllers have grown by leaps and bounds. Likewise, the applicationsof PLCs have grown with them. In fact, in toda...

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    xAbout the AuthorsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comABOUT THE AUTHORSLUIS BRYANLuis Bryan holds a Bachelor of Science in Electrical Engineering degree anda Master of Science in Electrical Engineering degree, both from the Univer-sity of Tennessee. Hi...

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    xiHow to Use this BookIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comHOW TO USE THIS BOOKWelcome to Programmable Controllers: Theory and Implementation. Be-fore you begin reading, please review the following strategies for using thisbook. By following these study...

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    INTRODUCTORYCONCEPTSSECTION ONE•Introduction to Programmable Controllers•Number Systems and Codes•Logic ConceptsIndustrial Text and Video Company 1-800-752-8398www.industrialtext.com

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    INTRODUCTION TOPROGRAMMABLE CONTROLLERSCHAPTERONEI find the great thing in this world is not somuch where we stand as in what direction weare moving.—Oliver Wendell HolmesIndustrial Text and Video Company 1-800-752-8398www.industrialtext.com

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    SECTION1IntroductoryConcepts4Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersFigure 1-1. PLC conceptual application diagram.CHAPTERHIGHLIGHTSProgrammable controllers have many definitions. However, PLCs can bethought of in si...

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    5CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsThe Hydramatic Division of the General Motors Corporation specified thedesign criteria for the first programmable controller in 1968. Their primaryg...

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    SECTION1IntroductoryConcepts6Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersIn a short period, programmable controller use started to spread to otherindustries. By 1971, PLCs were being used to provide relay replacement asth...

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    7CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsintegral-derivative), network, CANbus, fieldbus, ASCII communica-tion, positioning, host computer, and language modules (e.g., BASIC,Pascal).•Mech...

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    SECTION1IntroductoryConcepts8Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable Controllerssophisticated PLCs, with as many as 8,000 I/O points and 128,000 words ofmemory. These family members, using common I/O systems andprogramming perip...

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    9CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConcepts•Data handling and manipulation instructions have been improved andsimplified to accommodate complex control and data acquisitionapplications that...

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    SECTION1IntroductoryConcepts10Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersFigure 1-5. Programmable controller block diagram.Figure 1-6. Block diagram of major CPU components.ProcessorPowerSupplyMemoryThe central processin...

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    11CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsFigure 1-7. Illustration of a scan.The operation of a programmable controller is relatively simple. The input/output (I/O) system is physically con...

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    SECTION1IntroductoryConcepts12Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersFigure 1-9. (a) Personal computer used as a programming device and (b) a mini-programmer unit.Chapters 4 and 5 will present a more detailed discuss...

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    13CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConcepts1-4 PLCS VERSUS OTHER TYPES OF CONTROLSPLCS VERSUS RELAY CONTROLFor years, the question many engineers, plant managers, and originalequipment manu...

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    SECTION1IntroductoryConcepts14Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersIf system requirements call for flexibility or future growth, a programmablecontroller brings returns that outweigh any initial cost advantage of a...

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    15CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsA second distinction of PLCs is that their hardware and software are designedfor easy use by plant electricians and technicians. The hardware inter...

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    SECTION1IntroductoryConcepts16Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersThe personal computer is, however, being used as the programming device ofchoice for PLCs in the market, where PLC manufacturers and third-partyPLC...

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    17CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsSince its inception, the PLC has been successfully applied in virtuallyevery segment of industry, including steel mills, paper plants, food-process...

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    SECTION1IntroductoryConcepts18Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersTable 1-2. Examples of PLC applications.Because the applications of programmable controllers are extensive, it isimpossible to list them all in thi...

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    19CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsTable 1-2 continued.GSSALPGNISSECOR.lortnoCrheLgnilaennAssertslanretniehtevomerotdesurhelehtlortnocsCLPgnilaennaehtgniwollofybnoitarepoehtslortnocm...

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    SECTION1IntroductoryConcepts20Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersTable 1-2 continued..smetsySlaveirteRdnaegarotSnimehtyrracdnastrapdaolotdesusiCLPAenalaekilnoitamrofniskcartrellortnocehT.metsyslaveirterdnaegarots...

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    21CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsTable 1-2 continued..gnissecorPnoitazidiulFlaoCsiygrenehcumwohsrotinomrellortnocehTgniximdnagnihsurclaocehtsetalugerdnalaocfotnuomanevigamorfdetare...

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    SECTION1IntroductoryConcepts22Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersFigure 1-13. PLC product ranges.Micro PLCs are used in applications controlling up to 32 input and outputdevices, 20 or less I/O being the norm. Th...

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    23CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptscovers, in detail, the differences between PLCs in overlapping areas. Thesedifferences include I/O count, memory size, programming language, soft-w...

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    SECTION1IntroductoryConcepts24Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable Controllers1-6 LADDER DIAGRAMS AND THE PLCThe ladder diagram has and continues to be the traditional way of represent-ing electrical sequences of operations....

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    25CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsEXAMPLE 1-1In the hardwired circuit shown in Figure 1-15, the pilot light PL will turnON if the limit switch LS1 closes and if either push button P...

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    SECTION1IntroductoryConcepts26Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersFigure 1-17. Possible configurations of inputs and corresponding outputs.1-7 ADVANTAGES OF PLCSIn general, PLC architecture is modular and flexibl...

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    27CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsTable 1-3. Typical programmable controller features and benefits.Without question, the “programmable” feature provides the single greatestbenef...

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    SECTION1IntroductoryConcepts28Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersA typical example of the benefits of softwiring is a solenoid that is controlledby two limit switches connected in series (see Figure 1-19a). Chang...

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    29CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsconfiguration, a PLC can send useful English messages regarding thecontrolled system to an intelligent display. On the other hand, a PLC canreceive...

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    SECTION1IntroductoryConcepts30Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersIn large installations, remote input/output stations are placed at optimumlocations (see Figure 1-21). A coaxial cable or a twisted pair of wires c...

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    31CHAPTER1Introduction toProgrammable ControllersIndustrial Text and Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsEASE OF MAINTENANCE AND TROUBLESHOOTINGFigure 1-23. Failures in a PLC-based system.Figure 1-22. (a) A PLC processor and (b) an intelligent module c...

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    SECTION1IntroductoryConcepts32Industrial Text and Video Company 1-800-752-8398www.industrialtext.comCHAPTER1Introduction toProgrammable ControllersFigure 1-24. A programming device being used to monitor inputs and outputs,with highlighted contacts indicating an ON condition.KEYTERMSWith the ai...

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    NUMBER SYSTEMSAND CODESCHAPTERTWOI have often admired the mystical ways ofPythagoras and the secret magic of numbers.—Sir Thomas BrowneIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    34SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2CHAPTERHIGHLIGHTSIn this chapter, we will explain the number systems and digital codes that aremost often used in programmable controller applications. We ...

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    35CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comone less than the base (9 is one less than 10). Because the decimal system isso common, we rarely stop to think about how to express a number greaterthan 9,...

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    36SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2As you will see in other number systems, the decimal equivalent of anynumber can be computed by multiplying each digit by its base raised to thepower of th...

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    37CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAs with the decimal system, expressing binary numbers greater than thelargest-valued symbol (in this case 1) is accomplished by assigning aweighted value to...

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    38SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2Counting in binary is a little more awkward than counting in decimal for thesimple reason that we are not used to it. Because the binary number systemuses ...

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    39CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 2-2. Decimal, binary, and octal counting.As noted earlier, the octal numbering system is used as a convenient way ofwriting a binary number. The octal...

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    40SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2So, a 16-bit binary number can be represented directly by six digits in octal.As you will see later, many programmable controllers use the octal numbersyst...

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    41CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comLike octal numbers, hexadecimal numbers can easily be converted to binarywithout any mathematical transformation. To convert a hexadecimal numberto binary, ...

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    42SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2by 5, giving an N2 result and an R2 remainder that becomes the second base 5digit. This process is repeated until the result of the division (Nn ÷ 5) is 0...

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    43CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThus, the hexadecimal equivalent of 135510 is 54Bhex (remember that thehexadecimal system uses the letter B to represent the number 11).There is another met...

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    44SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2subtraction, multiplication, and division to be performed through successiveaddition. For example, to subtract the number 20 from the number 40, firstcompl...

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    45CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTWO’S COMPLEMENTThe two’s complement is similar to the one’s complement in the sense thatone extra digit is used to represent the sign. The two’s co...

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    46SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2ASCII2-4 BINARY CODESAn important requirement of programmable controllers is communicationwith various external devices that either supply information to ...

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    47CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAn 8-bit ASCII code is used when parity check (see Chapter 4) is added to astandard 7-bit code for error-checking purposes (note that all eight bits canstil...

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    48SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2The BCD representation of a decimal number is obtained by replacing eachdecimal digit with its BCD equivalent. The BCD representation of decimal7493 is sho...

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    49CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comGRAYFigure 2-8. (a) Thumbwheel switch converts decimal numbers into BCD inputs for the PLC.(b) The seven-segment display converts the BCD outputs from the P...

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    50SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2Figure 2-10. A 16-bit register/word.An example of a Gray code application is an optical absolute encoder. In thisencoder, the rotor disk consists of opaque...

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    51CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAlthough the data stored in a register is represented by binary 1s and 0s, theformat in which this binary data is stored may differ from one programmablecon...

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    52SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNumber Systemsand CodesCHAPTER2In BCD format, a 16-bit register can hold up to a 4-digit decimal value, withthe decimal values that can be represented ranging from 0000–9999. Figure2-1...

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    53CHAPTER2Number Systemsand CodesSECTION1ntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comKEYTERMSFigure 2-15. A 16-bit PLC register holding the BCD number 7815.01111000000101014 Bits4 Bits4 Bits4 BitsData SentFrom PLCMostSignificantDigitLeastSig...

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    LOGIC CONCEPTSCHAPTERTHREEScience when well digested is nothing butgood sense and reason.—Leszinski StanislasIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    56SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsCHAPTERHIGHLIGHTSTo understand programmable controllers and their applications, you mustfirst understand the logic concepts behind them. In this chapter, we willdis...

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    57CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsNegative logic, as illustrated in Table 3-2, uses 0 to represent the morepositive voltage level, or the occurrence of the event. Consequently, 1represents the nonoc...

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    58SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsAn AND function can have an unlimited number of inputs, but it can haveonly one output. Figure 3-2 shows a two-input AND gate and its resultingoutput Y, based on al...

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    59CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsFigure 3-3. Symbol for the OR function.THE OR FUNCTIONFigure 3-4. Two-input OR gate and its truth table.As with the AND function, an OR gate function can have an un...

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    60SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsSOLUTIONLine VoltageL1PB2PB1Line Voltage (Common)L2Electrical Ladder Circuit1BP2BPnroHmralA)0(dehsuptoN)0(dehsuptoN)0(tneliS)0(dehsuptoN)1(dehsuP)1(gnidnuoS)1(dehsu...

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    61CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsThe NOT function, unlike the AND and OR functions, can have only oneinput. It is seldom used alone, but rather in conjunction with an AND or an ORgate. Figure 3-6 s...

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    62SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsNote: In this example, the level switch L1 is normally open, but it closes when the liquidlevel reaches L1. The ladder circuit requires an auxiliary control relay (...

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    63CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsEXAMPLE 3-4Show the logic gate, truth table, and circuit representation for an alarmhorn that will sound if push button PB1 is 1 (ON or depressed) and PB2is NOT 0 (...

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    64SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsFigure 3-7. Two-input NAND gateand its truth table.3-3 PRINCIPLES OF BOOLEAN ALGEBRA AND LOGICThe two previous examples showed the NOT symbol placed at inputs to a...

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    65CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsFigure 3-9. Boolean algebra as related to the AND, OR, and NOT functions.relationship between digital logic and Boolean logic, you will occasionallyhear logic gates...

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    66SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsTable 3-3. Logic operations using Boolean algebra.3. Boolean Algebra Rules. Control logic functions can vary from simple to verycomplex combinations of input variab...

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    67CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsTable 3-3 continued.4. Order of Operation and Grouping Signs. The order in which Boolean opera-tions (AND, OR, NOT) are performed is important. This order will affe...

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    68SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConcepts3-4 PLC CIRCUITS AND LOGIC CONTACT SYMBOLOGYHardwired logic refers to logic control functions (timing, sequencing, andcontrol) that are determined by the way devic...

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    69CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsFigure 3-10b. PLC ladder diagram implementation of Figure 3-10a.The logic implemented in PLCs is based on the three basic logic functions(AND, OR, and NOT) that we ...

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    70SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsL1L2M1PB1STOPPB2STOPPB3STARTPB4STARTM1AllOL's1L1L1L2L2PB1PB3PB20120330 1230PB43M1AllOL's130(a)(b)Contact symbology is a very simple way of expressing control logic ...

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    71CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsThe symbols that represent the inputs are connected in series, parallel, or somecombination to obtain the desired logic. These input symbols represent theinput devi...

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    72SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsFigure 3-12. Electrical ladder circuit and its equivalent PLC implementation.Figure 3-13. Field devices from Figure 3-12 connected to I/O module.The same logic that...

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    73CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsFigure 3-14. Relay and PLC contact symbols showing a relay coil and normally openand normally closed contacts.connected to the interface with address 40. In order t...

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    74SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptsRemember that when a set of contacts closes, it provides power flow, orcontinuity, in the circuit where it is used. Each set of available coils and itsrespective co...

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    75CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsThe following seven points describe guidelines for translating fromhardwired logic to programmed logic using PLC contact symbols:•Normally open contact. When eval...

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    76SECTION1IntroductoryConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER3 LogicConceptstion point) or an internal output used exclusively within the pro-gram. An internal output does not control a field device. Rather, itprovides interlocking function...

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    77CHAPTER3 LogicConceptsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION1IntroductoryConceptsTable 3-6. (a) Hardwired relay logic translated into PLC logicusing contact symbols and (b) an explanation of the translation.SOL1LS1LS2X1X2Y1Series CircuitC1SOL2LS...

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    COMPONENTS ANDSYSTEMSSECTION TWO•Processors, the Power Supply, and ProgrammingDevices•The Memory System and I/O Interaction•The Discrete Input/Output System•The Analog Input/Output System•Special Function I/O and Serial CommunicationInterfacingIndustrial Text & Video Company ...

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    PROCESSORS, THE POWER SUPPLY,AND PROGRAMMING DEVICESCHAPTERFOURUnity makes strength, and since we must bestrong, we must also be one.—Grand Duke Friedrich von BadenIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    82SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesThe processor and the power supply are important parts of the centralprocessing unit. In this chapter, we will take a look a...

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    83CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe term CPU is often used interchangeably with the word processor;however, the CPU encompasses all of the necessary element...

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    84SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming Devicesprocessor executes the control program stored in the memory system in theform of ladder diagrams, while the system power sup...

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    85CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe CPU of a PLC system may contain more than one processor (or micro)to execute the system’s duties and/or communications...

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    86SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesThe microprocessors used in PLCs are categorized according to their wordsize, or the number of bits that they use simultaneo...

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    87CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemscall the solving of the control program the program scan and the reading ofinputs and updating of outputs the I/O update sca...

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    88SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming Devicessignal that changes states twice during an 8 msec period (less than the scan),the programmable controller will not be able t...

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    89CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsNote that although the signal in Figure 4-9a is shorter than the scan,the PLC recognizes it. However, the user should take p...

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    90SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesOne ScanReadUpdateOne ScanLogic 1Logic 0Logic 1Logic 0Program Execution50 µsecSignalEXAMPLE 4-2Referencing Figure 4-12, ill...

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    91CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsSOLUTION(a) As shown in Figure 4-13, the immediate instruction will interrupt thecontrol program to read the input signal. I...

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    92SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming Devices4-4 ERROR CHECKING AND DIAGNOSTICSFigure 4-15. Typical PLC subsystem configuration.The distance between the CPU and a subsy...

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    93CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe controller transmits data to subsystems at very high speeds, but the actualspeed varies depending on the controller. The...

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    94SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesLet’s suppose that a processor transmits the 7-bit ASCII character C(1000011) to a peripheral device and odd parity is req...

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    95CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemssummation process can rapidly reach an overflow condition, so one variationof CRC allows the sum to overflow, storing only t...

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    96SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesFigure 4-19. Cyclic exclusive-OR checksum operation.EXAMPLE 4-3Implement a checksum utilizing (a) LRC and (b) CX-ORC techniq...

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    97CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsLRC data block:word 11 1 0 0 1 1word 21 0 1 1 0 1word 31 0 1 1 1 0word 41 0 0 1 1 1BCC0 1 0 1 1 1(b) Cyclic exclusive-OR che...

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    98SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesThe most common error-detecting and error-correcting code is the Hammingcode. This code relies on parity bits interspersed w...

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    99CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTHE INPUT VOLTAGEUsually, PLC power supplies require input from an AC power source;however, some PLCs will accept a DC power...

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    100SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming Devicesformer must be properly rated to provide ample power to the load. The ratingof the constant voltage transformer, in units o...

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    101CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsIsolation Transformers. Often, a programmable controller will be installedin an area where the AC line is stable; however, ...

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    102SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesPower supply overloading can be an especially annoying condition, since theproblem is not always easily detected. An overlo...

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    103CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe first step in estimating the load is to determine how many modules arerequired and then compute the total current requi...

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    104SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming Devices4-6 PROGRAMMING DEVICESAlthough the way to enter the control program into the PLC has changed sincethe first PLCs came ont...

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    105CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemslimited by memory and display size. Intelligent miniprogrammers are micro-processor-based and provide the user with many of...

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    106SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesPERSONAL COMPUTERSCommon usage of the personal computer (PC) in our daily lives has led to thepractical elimination of dedi...

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    107CHAPTER4 Processors, the Power Supply,and Programming DevicesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 4-26. A PC connected to a PLC’s local area network.Figure 4-27. A PC acting as a bridge between a PLC network and ...

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    108SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER4 Processors, the Power Supply,and Programming DevicesIn addition to programming and data collection activities, PC software thatprovides ladder programming capability often inc...

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    THE MEMORY SYSTEM ANDI/O INTERACTIONCHAPTERFIVEThe two offices of memory are collection anddistribution.—Samuel JohnsonIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    110SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionCHAPTERHIGHLIGHTSThe most important characteristic of a programmable controller is the user’sability to change the control program quickly...

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    111CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsmemory where the system’s available instruction software is stored (i.e., relayinstructions, block transfer functions, math instructions, ...

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    112SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionREAD-ONLY MEMORYRANDOM-ACCESS MEMORYRead-only memory (ROM) is designed to permanently store a fixedprogram that is not alterable under ordin...

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    113CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 5-2. A 4K words by 8 bits RAM memory chip.PROGRAMMABLE READ-ONLY MEMORYProgrammable read-only memory (PROM) is a special type of ROMb...

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    114SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionAn application memory composed of EPROM alone is unsuitable if on-linechanges or data entry are required. However, many controllers offer EP...

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    115CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsOne of the disadvantages of EEPROM is that a byte of memory can be writtento only after it has been erased, thus creating a delay. This dela...

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    116SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionFigure 5-5. Block illustration of (a) a 4K by 8 bits storage location and (b) a 4K by16 bits storage location.The memory capacity of a progr...

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    117CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsAdditional information concerning how program instructions are stored willhelp to make a better decision. The term memory utilization refers...

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    118SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionSOLUTIONUsing the given information, a preliminary estimation of memory is:(a)Control logic = 10 contact elements/output rungNumber of outpu...

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    119CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemswill also have greater memory requirements. Depending on the PLC’smanufacturer, the application memory may also include the data table and...

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    120SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O Interaction•Scratch Pad Area. This is a temporary storage area used by the CPUto store a relatively small amount of data for interim calculations and...

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    121CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsData Table Section. The data table section of a PLC’s application memoryis composed of several areas (see Figure 5-7). They are:•the inp...

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    122SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionOutput Table. The output table is an array of bits that controls the status ofdigital output devices that are connected to the PLC’s outpu...

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    123CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 5-9. Field output connected to a bit in the output table.storage area (see Figure 5-10). The internal bit storage area contains stora...

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    124SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionFigure 5-10. Storage area section of the data table.Values placed in the register/word storage area represent input data from avariety of de...

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    125CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 5-12. Closed limit switch connected to an internal output.SOLUTIONWhen LS closes (see Figure 5-12), contact 10 will close, turningint...

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    126SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionEXAMPLE 5-3For the memory map shown in Figure 5-13, illustrate how to representthe following numbers in the storage area: (a) the BCD number...

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    127CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsWhen a PLC executes its program, the processor interprets the information inthe user program memory and controls the referenced bits in the ...

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    128SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionTo illustrate this memory map may seem unnecessary, but at this point, we donot know the starting address of the control program. This does ...

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    129CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsregisters, then, will end at address 00378 (see Figure 5-16). Any other 8-register increments will start at 00408, with the last possible ad...

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    130SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionThe input/output structure of a programmable controller is designed with onething in mind—simplicity. Input/output field devices are conne...

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    131CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 5-18. Input/output module connected to field devices.Figure 5-19. PLC ladder implementation of Figure 5-17 using an internal output b...

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    132SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionThe instructions used to represent the simple control program, shown inFigure 5-22, are stored in the user memory section, where specific bi...

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    133CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsLS0010001004070407PLFigure 5-22. Instructions used to represent the control program.5-7 MEMORY CONSIDERATIONSFigure 5-21. A simple circuit ...

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    134SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER5The Memory Systemand I/O InteractionFigure 5-23. Steps in the evaluation of the PLC circuit shown in Figure 5-22.010LSLS is open00100407PL020L1L2L1L204070407010LSLS is closedPr...

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    135CHAPTER5The Memory Systemand I/O InteractionIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsmeans that the user program area will be fixed. In larger controllers, however,the data table size is usually selectable, according to the d...

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    THE DISCRETEINPUT/OUTPUT SYSTEMCHAPTERSIXAll science is concerned with the relationshipof cause and effect.—Laurence J. PeterIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    138SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemCHAPTERHIGHLIGHTSInput/output (I/O) systems put the “control” in programmable controllers.These systems allow PLCs to work with field device...

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    139CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsCourtesy of Allen-Bradley, Highland Heights, OHFigure 6-2. Typical discrete input/output system.Figure 6-3. Example of an I/O rack enclosure.6-2...

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    140SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-4. Internal switches used to set I/O addresses.A rack, in general, recognizes the type of module connected to it (input oroutput) and t...

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    141CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-6. Local rack configuration.Figure 6-5. Master racks (a) without I/O modules and (b) with I/O modules.from the CPU. This bidirectional ...

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    142SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-7. Remote rack configuration.Remote Rack #1PowerSupplyMainLocationMaster RackCPURemote I/O10,000 feetRemote I/O ProcessorRemote Rack #2...

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    143CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTable 6-1. Specifications for the I/O rack enclosure example.Figure 6-8. Illustration of the example I/O rack enclosure (x = 1 for inputs, 0 for...

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    144SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemThe maximum capacity of this system is 512 inputs or 512 outputs, or a totalcombination of 512 inputs and outputs that do not overlap addresses....

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    145CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systems0123012301234567TerminalAddressModuleModuleOutputOutputOutputOutputInputInputInputEmptyRack 0012345670Slot123456776543210(a)(b)TakenTakenEmptyTa...

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    146SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-10. Output 0004 used as an internal coil.000400046-3 REMOTE I/O SYSTEMSIn large PLC systems (upwards of 512 I/O), input/output subsyst...

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    147CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemssubsystems may be installed and started up independently, allowing mainte-nance of individual subsystems while others continue to operate. Also,...

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    148SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemMany instructions are designed to manipulate discrete inputs. These instruc-tions handle either single bits, which control one field input conne...

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    149CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsEXAMPLE 6-1For the rack configuration shown in Figure 6-14, determine theaddress for each field device wired to each input connection in the 8-b...

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    150SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemSOLUTIONThe discrete input module (where the input devices are connected)will have addresses 070 through 077, because it is located in rack 0,sl...

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    151CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-16. Block diagram of an AC/DC input circuit.input field devices can be of different types and/or magnitudes (e.g., 120VAC, 12 VDC). For...

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    152SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemThe power section of an AC/DC input interface converts the incoming ACvoltage from an input-sensing device, such as those described in Table 6-2...

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    153CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-18. Device connections for (a) an AC input module and (b) a DC input modulewith common wire connection “C” used to complete the pat...

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    154SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemDuring interfacing, the user must keep in mind the minimum and maximumspecified currents that the input devices and module are capable of sinkin...

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    155CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-21. Conversion circuit interfacing a sinking output with a sourcing inputmodule.The majority of DC proximity sensors used as PLC inputs...

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    156SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-22. Device connection for an AC/DC isolated input interface.L1AL1CACL1B1C122C33C44C55CL2AL2CACL2BUser DCPowerSupply–+Isolated input i...

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    157CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsfaces will lose inputs, because to keep isolation among inputs, they can haveonly one input line per return line. For example, a 16-point standa...

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    158SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output Systemwith thumbwheel switches if these input devices are TTL compatible. Figure6-24 illustrates a typical TTL input module connection diagram with an...

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    159CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-25. BCD interface inputting parameters into register/word locations in memory.Figure 6-26. Register or BCD input module connection diag...

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    160SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-29. A 4-digit TWS with one common enable line.Figure 6-27. Multiplexing input module connection diagram.Figure 6-28. Single-digit TWS w...

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    161CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-30. Block diagram of a multiplexed input module connected to four 4-digit TWS.EXAMPLE 6-2Referencing Figure 6-30, determine the values ...

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    162SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemSOLUTIONThe contents of register 4000 in BCD will be the BCD code equivalentof the first set of thumbwheel switches connected to the PLC registe...

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    163CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-33. Functional block instruction transferring the output register contents tothe module.(e.g., 120 VAC) to the output field device, tur...

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    164SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemEXAMPLE 6-3For the rack configuration shown in Figure 6-34, determine theaddresses for each of the output field devices wired to the outputconne...

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    165CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-36. AC output circuit block diagram.AC OUTPUTSFromProcessorIsolatorLogicSwitchFilterPowerIsolationLogicPower LEDLogicLEDLineLoad6-7 DI...

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    166SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemDuring normal operation, the processor sends an output’s status, accordingto the logic program, to the module’s logic circuit. If the output...

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    167CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsAs with input circuits, AC output interfaces may have LEDs to indicateoperating logic signals and power circuit voltages. If the output circuitc...

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    168SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemIn a sourcing module configuration, current flows from the module into theload, switching the positive voltage to the load. Figure 6-40 illustra...

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    169CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsA standard, nonisolated output module has one return connection for all of itsoutputs; however, some modules provide one return line per four ou...

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    170SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-44. Register/BCD output interface connected to seven-segment indicators.output interfaces provide voltages ranging from 5 VDC (TTL leve...

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    171CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-45. Output data table sending a 16-bit word to a register output module.BCDMODULEMemoryBlock transferout instructionDataWord/RegisterSt...

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    172SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemThe use of multiplexed outputs does not require special programming, sincethere are output instructions that specify the multiplexing operation....

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    173CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-49. A multiplexed output module with four sets of LED displays.3 2 1EN 1EN 2EN 3EN 400010203040506071011121314151617432 1432 1432 14444...

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    174SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-52. Timing diagram of enable signals from a BCD multiplexed module.Figure 6-51. Storage table for Example 6-4.EN1EN2EN3EN41st Scan2nd S...

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    175CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-53. Multiplexed output module for Example 6-4.3 2 1BCD#1BCD#2BCD#4EN 1EN 2EN 3EN 4000102030000100000011100040506071011121314151617BCD#3...

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    176SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemFigure 6-55. Example of a contact interface connection.1A1B2A2B3A3B4A4BInsideModuleTo speed drive controllerAnalog VoltageReference 1Analog Volt...

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    177CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 6-56. Typical bypass device.Figure 6-57. Bypass unit placed between the PLC and a field device.L1L2ONOFFAutoONON—Output is forced ONOFF...

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    178SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output System6-9 INTERPRETING I/O SPECIFICATIONSELECTRICALPerhaps with the exception of standard I/O current and voltage ratings,specifications for I/O circ...

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    179CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTable 6-6. Summary of I/O specifications.ELACIRTCEL.gnitaRegatloVtupnIdnaedutingamehtseificepstahteulavCDroCAnA.tpeccalliwtiucricalangisfoepyt.g...

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    180SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output Systemspecification may also be stated as the output voltage range, in which caseboth the minimum and maximum operating voltages are given. An outputc...

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    181CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsOutput-ON Delay. This specification defines the response time for the outputto go from OFF to ON once the logic circuitry has received the comma...

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    182SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemENVIRONMENTALMECHANICALPoints Per Module. This specification defines the number of input/outputcircuits that are on a single module (encasement)...

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    183CHAPTER6The DiscreteInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsAll I/O interfaces accept input status data for the input table and acceptprocessed data from the output table. This information is placed in or...

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    184SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER6The DiscreteInput/Output SystemKEYTERMSAC/DC I/O interfacebypass/control stationcontact output interfaceDC I/O interfacedigital signaldiscrete input interfacediscrete output i...

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    THE ANALOGINPUT/OUTPUT SYSTEMOne line alone has no meaning; a second oneis needed to give it expression.—Eugène DelacroixCHAPTERSEVENIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    186SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemCHAPTERHIGHLIGHTSAlthough discrete I/O systems are invaluable tools for PLC controls, theycannot meet all the demands of new technological and app...

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    187CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsPLCs, like other digital computers, are discrete systems that only understand1s and 0s. Therefore, they cannot interpret analog signals in their c...

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    188SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemFigure 7-4. Steps in converting an analog signal to binary format.EXAMPLE 7-1What will the contents of register 1000 be after the multibit instruc...

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    189CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-6. Conversion of an analog signal by a transmitter and transducer.Due to the many types of transducers available, analog input modules ha...

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    190SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output Systemmeasured by the field device. The field sensing device sends a very low-levelcurrent or voltage analog input to the transmitter. The transmitter (...

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    191CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-8. An analog-to-digital converter with 12-bit resolution.Table 7-3. Psi values translated into decimal equivalents and engineering units....

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    192SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemFigure 7-9. An A/D and an analog input module connected to a temperature-sensing device.EXAMPLE 7-2An input module, which is connected to a temper...

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    193CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe change in voltage for each input count is:The changes in temperature, voltage, and counts are 500°C, 4 VDC,and 1023 counts. The voltage chang...

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    194SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemFigure 7-10. Temperature transducer/transmitter connected to an input module.Figure 7-11. Relationship between counts and input signal.EXAMPLE 7-3...

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    195CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTo find the relationship between temperature and counts, find thenumerical representation of the equation for line Y. This equation takesthe form ...

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    196SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemThus, the count value for 100°C is 409.5 counts and for 500°C is 2047.5counts. Since count values must be whole numbers, rounding thesevalues of...

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    197CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-12. Process for inputting analog data to a word location.Voltage SignalReturn LineAnalogInputModuleAnalog InputInstructionUsedA/D12 Bits0...

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    198SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output Systemread, the processor reads and stores one channel every scan. This does notcause a delay in signal processing, since the scan is very fast and the ...

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    199CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-14. Bits within a register indicating the status of each channel.7-5 ANALOG INPUT CONNECTIONSAnalog input modules usually provide a high...

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    200SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output System12345678C11C22C33C44CAnalogSignalTransmitter+–AnalogSignalTransmitter+–(a) Single-ended inputsAnalogSignalTransmitter+–AnalogSignalTransmitt...

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    201CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsAnalog output interfaces are used in applications requiring the control of fielddevices that respond to continuous voltage or current levels. An e...

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    202SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output Systemto analog and passes it to the field control device. Figure 7-18 illustrates amultibit instruction transferring 12 bits of data from register 2000...

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    203CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-19 illustrates the binary transfer of information to an analogoutput module via a multibit instruction. Assume that the outputmodule conv...

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    204SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemAn analog output interface operates much like an analog input module, exceptthat the data direction is reversed. As mentioned earlier, a PLC proce...

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    205CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe resolution of a digital-to-analog converter is defined by the number of bitsthat it uses for the analog conversion. For example, a D/A with a ...

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    206SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemFigure 7-22. Relationship between counts, voltage, and percentage.To formulate the desired table, first determine the equivalent values foreach va...

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    207CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTable 7-7. Equivalent counts, voltages, and percentages.7-9 ANALOG OUTPUT DATA HANDLINGIn the previous section, we explained how a module transfe...

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    208SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemFigure 7-23. Transformation of binary storage table data into an analog signal.Voltage SignalReturn LineAnalogOutputModuleAnalog OutputInstruction...

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    209CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsSome PLC manufacturers offer software instructions that scale data withinthe module or during the execution of the analog output instruction. Scal...

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    210SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemEXAMPLE 7-6A programmable controller uses a bipolar –10 to +10 VDC signal tocontrol the flow of material being pumped into a reactor vessel. The...

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    211CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-26. Representation of percentage opening and analog output counts.SOLUTION(a) Figure 7-26 shows line Y, which represents the number of co...

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    212SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output SystemThis equation gives the value of Y in counts for any voltage X. Theequation of line Y as a function of percentage can be computed in asimilar mann...

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    213CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe equation for line Y showing the relationship between output countsand register value is: Y= mX+ bm=∆counts∆register value=81909999Y=819...

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    214SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER7The AnalogInput/Output System12345678C11C22C33C44CAnalogTransducer+–AnalogTransducer+–(a) Single-ended outputsAnalogTransducer+–AnalogTransducerAnalogOutputDeviceAnalogO...

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    215CHAPTER7The AnalogInput/Output SystemIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 7-29. Block diagram of bypass/control backup unit.KEYTERMSpneumatic converters. This can be done without the PLC or prior to itscheckout. W...

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    SPECIAL FUNCTION I/O AND SERIALCOMMUNICATION INTERFACINGCHAPTER EIGHTNo rule is so general, which admits not someexception.—Robert BurtonIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    218SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingIn previous chapters, we discussed analog and digital I/O interfaces.Although these types of interfaces allow control im...

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    219CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-1. Direct action I/O interface application.Figure 8-2. Intelligent I/O interface application.MemoryDirectAction...

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    220SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingIn the next sections, we will discuss the most commonly found special I/Ointerfaces:•special discrete•special analog...

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    221CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsConnections to fast-input modules are the same as for standard DC inputmodules. Depending on the module, the field devic...

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    222SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication Interfacingrange from 15 to 30 VDC. Although it is unlikely to occur, the total wireresistance of the connecting wire must not exce...

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    223CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFast-response modules have advantages that include the ability to respond tovery fast input events, which require an alm...

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    224SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication Interfacing8-3 SPECIAL ANALOG, TEMPERATURE, AND PIDINTERFACESFigure 8-7. Fast-response interface.Figure 8-8. Allen-Bradley’s fas...

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    225CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-9. Weight input application configuration.Figure 8-10. Allen-Bradley’s Weigh Scale Module (1771-WS).A weight ...

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    226SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingTHERMOCOUPLE INPUT MODULESIn addition to standard analog voltage/current input interfaces that canreceive signals direct...

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    227CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsanother may provide 100 ohms. If the lead resistance is greater than theavailable compensation, a calculation in the con...

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    228SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingSOLUTIONThe total lead resistance is computed as:Lead resistanceThermocouple lead resistance Lead wire length)ohms===()(...

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    229CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTable 8-1. Common RTD types and their specifications.RTD device is the 3-wire RTD. This type of device is used in applic...

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    230SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication Interfacingcontrol actions according to sensed parameters, such as pressure and tempera-ture, which are the input variables to the ...

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    231CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe following equation defines one of the control algorithms implemented bya PID module:VK EKEdtKdEdtPIDout =++∫where:...

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    232SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingA PID module receives primarily control parameter and set point informa-tion from the main processor. The module can als...

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    233CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsDepending on the module used, PID interfaces can also receive data aboutthe update time and the error deadband. The upda...

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    234SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingENCODER/COUNTER INTERFACESFigure 8-18. Positioning interface configuration.Encoder/counter modules interface encoders an...

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    235CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsrotation over distance by outputting a fixed number of pulses per shaftrotation. The module provides two pulse signals t...

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    236SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingThe motion of a stepper can be accelerated, decelerated, or maintainedconstantly by controlling the pulse rate output fr...

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    237CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsA stepper interface generates a pulse train that is compatible with the steppertranslator, indicating distance, rate, an...

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    238SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingSOLUTIONTo compute the step angle, divide the number of degrees in onerevolution (360°) by the number of steps required...

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    239CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsContinuousRateContinuousRateContinuousRateEnd ofmove 1End ofmove 2End ofmove 3Move 1Move 2Move 3StartMoveStartMoveFinalP...

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    240SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingEach stepper interface used to control a stepper motor controls an axis, sincethe motion generated causes a movement abo...

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    241CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-25. (a) Independent axis control and (b) synchronous axis control.Move 1Move 2Axis 1-XMove 3Move 1Move 2Move 3M...

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    242SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingThe use of a position/velocity feedback scheme (see Figure 8-26) can greatlyimprove the operation of a stepper motor con...

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    243CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-27. Stepper motor interface with jog forward and jog reverse capabilities.typical stepper motor interface conne...

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    244SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingServo positioning controls operate in a closed-loop system, requiring feed-back information in the form of velocity or p...

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    245CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-30. Servo control in (a) single-step and (b) continuous modes.Figure 8-29. Servo control block diagram.MotorTac...

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    246SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-31. Servo motor interface connection diagram.systems, the term feed velocity indicates a period of constant vel...

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    247CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsEXAMPLE 8-3A PLC system uses a servo interface to perform a one-axis position-ing of a metal part. This part will be mac...

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    248SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-32. Leadscrew (linear) displacement system.Thus, a metal part moving 12.5 inches will generate a positionfeedba...

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    249CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsLocal and remote I/O processors fall into the proprietary category ofcommunication interfaces, since they communicate in...

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    250SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingEXAMPLE 8-4A PLC system, which has a scan time of approximately 15 msec, usesa standard nonintelligent ASCII module. Thi...

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    251CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systems10 bits (7 for the code plus start, stop, and parity bits) that are usedduring each character transmission.The inverse o...

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    252SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication Interfacing(using the terminal), upon recognition of a user-defined data decodingsignal transferred from the PLC, or after the powe...

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    253CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-34. (a) Mitsubishi’s MELSECNET/B interface and (b) Allen-Bradley’s CANbusnetwork interface.A network interf...

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    254SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingNetwork ModuleNetworkInterfaceEthernetInterfaceNetworkInterfaceCANbusInterfaceFieldbusInterfaceTerminatorTerminatorLocal...

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    255CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-36. Fuzzy logic interface application.ProcessFuzzyModuleFuzzy implementationin moduleDecision makingbased on fu...

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    256SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-38. Example of a fuzzy logic algorithm.systems usually provide gross input deviations or insufficient input res...

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    257CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFuzzy logic control is even more practical when multiple rules exist. Forexample, a fuzzy I/O module may receive data fr...

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    258SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-40 shows Omron Electronics’s Fuzzy Logic Unit (FLU), a fuzzylogic interface that can read process data from u...

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    259CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTable 8-2. Omron’s FLU space requirements.•Like the first word, the first four bits (0–3) of the third word (word1...

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    260SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-42. Data transfer between I/O modules and fuzzy module.Block transfer instructions can be used to transfer data...

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    261CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemselectronics organizations, such as the Institute of Electrical and ElectronicsEngineers (IEEE) and the Electronic Indust...

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    262SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingEIA RS-232C. The EIA RS-232C is a proclaimed standard that defines theinterfacing between data equipment and communicati...

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    263CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsTable 8-3. EIA RS-232C data line descriptions.rebmuNniPnoitpircseD1dnuorgevitcetorP2ataddettimsnarT3ataddevieceR4dnesott...

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    264SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-44. RS-232C communication connections for (a) a PLC to a modem, (b) a PLC toa computer, and (c) a PLC to a prin...

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    265CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systems•The drivers used must be able to withstand open or short circuitsbetween pins in the interface.•The load impedance ...

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    266SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingA balanced circuit in an RS-422 configuration employs differential signalingover a pair of wires for each circuit, while...

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    267CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsThe maximum allowable cable distance for the RS-422 standard is a functionof the data transmission rate. Figure 8-47 ill...

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    268SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication Interfacinga network (e.g., multiple transmitters and receivers operated on a commonmedia, such as twisted-pair cable). Distances o...

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    269CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand Systemsvoltage-oriented interface, thus allowing the current loop interface to drivesignals longer distances. To avoid this vol...

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    270SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingFigure 8-51 shows the relationship between transmission distance and datarate for the RS-485 interface converter. This d...

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    271CHAPTER8Special Function I/O andSerial Communication InterfacingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION2Componentsand SystemsFigure 8-51. Baud rates for transmission distances in a RS-485 converter.Figure 8-52. PLC processors connected to an iso...

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    272SECTION2Componentsand SystemsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER8Special Function I/O andSerial Communication InterfacingASCII I/O interfacesBASIC modulecold junction compensationdirect action I/O interfacedistributed I/O processingencoder/c...

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    PLCPROGRAMMINGSECTION THREE•Programming Languages•The IEC 1131 Standard and Programming Language•System Programming and Implementation•PLC System DocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

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    PROGRAMMINGLANGUAGESCHAPTER NINELanguage is only the instrument of science,and words are but the signs of ideas.—Samuel JohnsonIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    276SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesThe programming languages used in programmable controllers have beenevolving since the inception of the PLC in the late 1960s. In this chapter, wewill introduce th...

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    277CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe ladder and Boolean languages essentially implement operations in thesame way, but they differ in the way their instructions are represented andhow they are ent...

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    278SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesNew additions to the basic ladder logic also include function blocks, whichuse a set of instructions to operate on a block of data. The use of functionblocks incre...

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    279CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingline that defines the grouping of PLC ladder instructions, however, is usuallydrawn between functional instruction categories. These instruction catego-ries includ...

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    280SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesadvanced instruction sets. However, recent advances in software develop-ment and I/O hardware have increased the computational power of smallPLCs through advanced ...

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    281CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingGRAFCETGrafcet (Graphe Fonctionnel de Commande Étape Transition) is a symbolic,graphic language, which originated in France, that represents the controlprogram as...

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    282SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-5. Grafcet translation.9-3 LADDER DIAGRAM FORMATThe ladder diagram language is a symbolic instruction set that is used tocreate PLC programs. The ladder ...

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    283CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingA ladder rung is TRUE (i.e., energizing an output or functional instructionblock) when it has logic continuity. Logic continuity exists when powerflows through the...

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    284SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesWhen a ladder diagram contains a functional block, contact instructions areused to represent the input conditions that drive (or enable) the block’s logic.A func...

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    285CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe ladder rung matrix determines the maximum number of laddercontact elements that can be used to program a rung (see Figure 9-11). Thesize of this matrix differs...

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    286SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesthe matrix (see Figure 9-12a). In PLCs with enhanced ladder formatfunctional instructions instead of block-type instructions, the ladder matrixmay use one or more ...

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    287CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-13. Reverse power flow at contact D.EXAMPLE 9-1Solve the logic rung shown in Figure 9-13 so that no reverse powerflow condition exists. The reverse condit...

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    288SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesEXAMPLE 9-2Solve the ladder logic shown in Figure 9-13 so that no reverse powerflow exists. Assume that the reverse path logic through contact D andthen forward th...

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    289CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming9-4 LADDER RELAY INSTRUCTIONSLadder relay instructions are the most basic instructions in the ladderdiagram instruction set. These instructions represent the ON/O...

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    290SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-17. (a) An examine-ON instruction with a logic 0 reference address and (b) anexamine-ON instruction with a logic 1 reference address.The relay-type instru...

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    291CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingAn examine-OFF instruction, also called a normally closed (NC) contactinstruction, tests for an OFF condition in the reference address. Like anexamine-ON instructi...

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    292SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesDuring the execution of an output coil instruction, the processor evaluates allthe input conditions in the ladder rung. If no continuity exists, the processorplace...

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    293CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingnormally closed contacts driving an output rung. For output 20 to turn ON,two things must happen: (1) PB1 must be pushed to turn ON reference input10 and (2) limit...

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    294SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesEXAMPLE 9-3(a) Implement the equivalent ladder rung logic shown in Figure 9-21using a NOT output coil instruction, and (b) implement the NOT Y logicwithout using a...

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    295CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-23. Implementation of the NOT Y logic without a NOT coil.LATCH OUTPUT COILLA latch coil instruction causes an output to remain energized even if thestatus...

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    296SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesLatch and unlatch instructions may occur in block form as shown in Figure9-25. The only difference between the ladder and block forms is that, in blockform, latchi...

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    297CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingDepending on the controller used, a one-shot output may trigger a leading-edge or a trailing-edge signal. A leading-edge trigger turns the one-shotoutput ON for on...

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    298SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguages9-5 LADDER RELAY PROGRAMMINGLADDER SCAN EVALUATIONScan evaluation is an important concept, since it defines the order in whichthe processor executes a ladder diag...

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    299CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-29. Ladder rung where the outputs turn ON in different scans.therefore, output 103 stays OFF. (2) In the second rung, contact 101 is OFF;therefore, output...

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    300SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguages10100L11100U1211OS10100L11100U1211(a)(b)Figure 9-30. (a) The one-shot output and (b) the transitional contact will never unlatchcoil 100.PROGRAMMING NORMALLY CLOSE...

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    301CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingL1L1L2L21010100PL1PB1100Figure 9-33. Logic implementation with PB1 programmed as a normally open contact.In Figure 9-32, the reference address of PB1 (input 10) is...

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    302SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesThe programming solution for a normally closed input connection, as shownin Figure 9-33, exemplifies the following: for a normally closed wired inputdevice to beha...

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    303CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingof PB1’s two connections (A or B) to the input module to satisfy therequired logic. Remember that we can make any contact act as wedesire in the PLC program (i....

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    304SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-38. Normally closed implementation of Figure 9-36.closed as long as PB1 is not pushed. The first rung implements a pushbutton wired as normally closed to ...

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    305CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-39. Normally closed stop push button programmed as normally open.Figure 9-40. Normally open stop push button programmed as normally closed.101011100Motor1...

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    306SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguages9-6 TIMERS AND COUNTERSPLC timers and counters are internal instructions that provide the samefunctions as hardware timers and counters. They activate or deactiva...

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    307CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingpreset register, while the accumulated value is kept in an accumulatedregister. Both of these registers are defined during the programming of theinstruction. Eithe...

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    308SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagessnoitcurtsnIremiT)CLPaniseitilibapacremiterawdrahedivorpoT:esopruP(noitcurtsnIlobmySnoitcnuFezigrenEyaleD-NOremiTemittesaretfatuptuonasezigrenEstsixe1cigolnehwdoir...

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    309CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingenable/reset line. If the control line is TRUE (i.e., it has continuity) and theenable line is also TRUE, the block function will start timing. A ladder formattime...

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    310SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguageshardwired timer contacts. Timer TMR1 in line 1 has an instantaneouscontact in line 2 (TMR1-1), which is used to seal PB1, and a time-delaycontact (TMR1-2) in line ...

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    311CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingOFF-DELAY ENERGIZE TIMERFigure 9-45. Timing diagram for (a) an ON-delay energize timer and (b) an ON-delayde-energize timer.Figure 9-46. OFF-delay energize timer i...

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    312SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguages9-8 COUNTER INSTRUCTIONSThere are two basic types of counters: those that can count up and those thatcan count down. Depending on the controller, the format of th...

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    313CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingsnoitcurtsnIretnuoC)CLPaniseitilibapacretnuocerawdrahedivorpoT:esopruP(noitcurtsnIlobmySnoitcnuFretnuoCpUretsigerdetalumuccaehtsesaercnItnevedecnereferaemityreveeu...

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    314SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesin the preset register). Also, this counter can keep track of the number of parts(e.g., filled bottles, machined parts, etc.) that pass a certain point. An upcount...

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    315CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-49. Counter function block with up, down, and reset counter instructions.EXAMPLE 9-6Figure 9-50 illustrates a block counter instruction being used to coun...

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    316SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-52. Solution to Example 9-7.Figure 9-51. Automatically resetting counter.EXAMPLE 9-7Referencing the solution to Example 9-6 (i.e., see Figure 9-51),implem...

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    317CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming9-9 PROGRAM/FLOW CONTROL INSTRUCTIONSProgram/flow control instructions direct the flow of operations, as well asthe execution of instructions, within a ladder pro...

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    318SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagessnoitcurtsnIlortnoCwolF/margorP)margorpreddalanisnoitcurtsnifonoitucexe/noitaulaveehttceridoT:esopruP(noitcurtsnIlobmySnoitcnuFyaleRlortnoCretsaMnoitucexeehtsetavi...

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    319CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingrungs. The fence consists of an MCR rung with conditional inputs at thebeginning of the zone and an END rung with no conditional inputs at the endof the zone. When...

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    320SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesaddress tells the processor to jump to the ladder rung with a label (LBL)instruction having the same reference number. The processor then continuesthe program exec...

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    321CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-56. PLC with assigned subroutines at the end of the program.Figure 9-57. User-created subroutine area.Main ControlProgramMain ControlProgramSubroutine #1S...

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    322SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagessnoitcurtsnIcitemhtirA)atadretsigerhtiwsnoitcnuflacitamehtammrofrepotsCLPwollaoT:esopruP(noitcurtsnIlobmySnoitcnuFreddaL—noitiddAowtniderotsseulavehtsddAsretsige...

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    323CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-58. (a) Coil, (b) contact, and (c) block format arithmetic instructions.Like other instructions, arithmetic instructions may be in either the basicladder ...

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    324SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesADDITION—LADDERFigure 9-60. Arithmetic operations performed in block form.instructions to obtain the arithmetic operands. In functional block format,some manufac...

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    325CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-61. Ladder format addition.ADDITION—BLOCKAn addition (ADD) functional block adds two values stored within thecontroller and places the sum in a specifie...

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    326SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesA control line enables the operation of an addition block. When the rungconditions are TRUE, the processor performs the addition function. In theblock shown in Fig...

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    327CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-64. Flow of two ingredients into a reactor tank.Figure 9-65. Solution to Example 9-8.SOLUTIONOne register can hold the total of both ingredients after the...

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    328SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesSUBTRACTION—BLOCKThe subtraction (SUB) functional block, as in the ladder format subtractioninstruction, finds the difference between two values and stores the r...

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    329CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-68. Subtraction block with sign outputs.Figure 9-69. Subtraction block used to (a) read an analog input and (b) write ananalog output.include a sign bit. ...

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    330SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-70. Ladder format multiplication instruction.One or two output coils reference the two result registers in a multiplicationinstruction, depending on the P...

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    331CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-71. Multiplication functional block.tion is held temporarily in two registers and then multiplied by a scale value(see Figure 9-72). For example, assume t...

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    332SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesDIVISION—LADDERA division (DIV) instruction finds the quotient of two numbers. This quotientis held in two result registers and referenced by the output coil. Th...

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    333CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe square root instruction is useful in applications like the calculation offlow rate from a differential pressure (DP) orifice flow meter (see Figure 9-76). In t...

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    334SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguages9-11 DATA MANIPULATION INSTRUCTIONSData manipulation instructions are enhancements of the basic ladderdiagram instruction set. Whereas relay-type instructions are...

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    335CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 9-8. Data manipulation instructions.Comparison instructions that use the basic ladder format operate in a mannersimilar to arithmetic instructions (see Figur...

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    336SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-79. Comparison block using a limit instruction.Figure 9-78. (a) Single-comparison and (b) multicomparison functional blocks.tions are greater than (>),...

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    337CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingwhether register 1200 is greater than or equal to register 1300 (i.e., R1100 ≥R1200 ≥ R1300). If the comparison is TRUE, the limit instruction energizesthe com...

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    338SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-81. Solution to Example 9-9.LOGIC MATRIXA logic matrix functional block performs AND, OR, exclusive-OR, NAND,NOR, and NOT logic operations on two or more ...

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    339CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-82. Logic matrix functional block.Figure 9-83. Logic matrix function block used to mask out bits.During its operation, a logic matrix function block has t...

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    340SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-84. Logic matrix function block example.DATA CONVERSIONSData conversion instructions change the contents of a given register from oneformat to another. Ty...

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    341CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramminginstruction. It then places the result of the conversion in the second registerand energizes the block output when the instruction is finished. Some PLCsallow mult...

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    342SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-88. Absolute/complement/invert functional block.Figure 9-87. Multiple-register binary-to-BCD conversion.Absolute, complement, and invert operations usuall...

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    343CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingSET CONSTANT PARAMETERSSometimes a constant value, which will be used later in the program forcomparisons or set points must be stored in a register. For this reas...

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    344SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-92. Right-rotate execution.SHIFT AND ROTATEA shift (SHIFT) instruction moves the bits in a register to the right or to theleft. Figure 9-91 illustrates th...

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    345CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-93 illustrates functional blocks for both the shift and rotate func-tions. The control input enables the blocks’ operation. Some block instruc-tions hav...

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    346SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesEXAMPLE 9-10A PLC application controls a batching process where the reading ofa temperature input (Batch Temp) is critical to the process. Theprocess’s temperatu...

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    347CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-96. Analog input interface for a batching application.Figure 9-97. A fault has occurred if register 1000 bit 17 is 0 (OFF).instruction is a contact that i...

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    348SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguages9-12 DATA TRANSFER INSTRUCTIONSData transfer instructions move, or transfer, numerical data within a PLC,either in single register units or in blocks (a group of ...

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    349CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 9-9. Data transfer instructions.Some PLCs perform a move function to special word table locations. In thiscase, the PLC automatically coverts the copied data...

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    350SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesReg 1000MaskReg 2000Reg 1100MOVM10010Move with maskYet another move instruction found in some controllers is the move statusinstruction. This block function ...

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    351CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTABLE MOVEA table move instruction transfers data from a block or table to a register orword in memory. There are two types of table move instructions: table-to-re...

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    352SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesEXAMPLE 9-11A batching system operates during an eight-hour shift, where severalbatch sizes are processed at the rate of approximately one batch perhour. Implement...

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    353CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-103. Register-to-table instruction used for storing batch information.increment. The increment occurs after both register-to-table instruc-tions have been...

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    354SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-106. Block transfer in instruction.BLOCK TRANSFER—IN/OUTSome PLCs provide block transfer (BXFER) instructions, which are prima-rily used with special I/...

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    355CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe control input activates an ASCII transfer (in or out) instruction. Whenreading data, the instruction allows the special I/O module to perform a readfunction. T...

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    356SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-108. FIFO functional block.Some ASCII transfer instructions use a pointer register to access specificcharacters in the table (e.g., to decode a specific i...

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    357CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingA FIFO operation consists of two parts: a FIFO input (FIFO IN) instructionand a FIFO output (FIFO OUT) instruction. The FIFO IN instruction loadsthe queue, while t...

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    358SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesSEQUENCERScomputing the median of sample readings—an operation that requires thesample to be in numerical order. PLCs provide either ascending, descending,or bot...

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    359CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming8 to 64 or more. The width of the table may also vary, as may the size of acylinder. Through I/O registers, which map real output points, each step in asequencer t...

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    360SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesEXAMPLE 9-12A PLC application calls for the implementation of ten different stepsthat take place in a sequential manner. For the purpose of detectinga fault in a t...

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    361CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-114b. Seven-segment display.DIAGNOSTICSA diagnostics (DIAG) block instruction compares two memory blocks, onecontaining actual input conditions and the ot...

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    362SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-116. PID functional block.An energized control input enables a PID block’s automatic operation. Thebottom input track, when energized, determines whethe...

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    363CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-117. Fill-in-the-blanks screen.control, while the middle and bottom outputs indicate low- and high-limitalarms, respectively. Some PLC manufacturers provi...

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    364SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesTable 9-11. Network communication instructions.Once a PLC executes a network communication instruction and updates it atthe EOS, the processor passes the informati...

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    365CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramminginternal outputs, 64 of them may be used as network outputs; likewise, if it has128 storage registers, 32 of them may be used as network registers. Thesenetwork-ma...

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    366SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesNETWORK CONTACTA network contact instruction captures the status information from a networkoutput. The reference address of the network contact must be the same as...

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    367CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingthe contents of the register to the network line. The instruction may providetwo outputs to indicate that the operation has been performed and that noerror was det...

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    368SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesFigure 9-121. Send node functional block operation.SEND NODEA send node (SEND NODE) instruction operates in a more direct way thana network send function. This ins...

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    369CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-122. Get node functional block operation.9-15 BOOLEAN MNEMONICSAs discussed in Section 9-2, Boolean mnemonics is a PLC language basedprimarily on the Boo...

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    370SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagescinomenMnoitcnuFnoitpircseDtnelaviuqEreddaLRTS/DLtrats/daoLtcatnocONahtiwecneuqescigolastratSTONRTS/RLtontrats/daoLtcatnocCNahtiwecneuqescigolastratSDNAtniopdnAnoi...

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    371CHAPTER9ProgrammingLanguagesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 9-123. Boolean program and its ladder diagram representation.KEYTERMS100101112102232425101END 2102021T 20013144011617MCR 21015CTU 22022PR: 10TB: 1 SecPR: 5S...

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    372SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER9ProgrammingLanguagesnetwork communications instructionsprogram/flow control instructionssingle-precision arithmeticspecial function instructionstimer instructionsnetwork communication...

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    THE IEC 1131 STANDARD ANDPROGRAMMING LANGUAGECHAPTER TENThought is the blossom; language the openingbud; action the fruit behind it.—Henry Ward BeecherIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    374SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageAs we have discussed in the previous chapters, programming a PLC can bea difficult task due to increased interlocking requirements in the...

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    375CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe IEC 1131 programming language standard is referred to as the IEC1131-3 programming standard, since part 3 of the standard deals withp...

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    376SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming Languageaddition, etc.). Function blocks are sets of data function instructions thatwork on blocks of data. Moreover, variable scope refers to th...

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    377CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingDECLARING VARIABLESDuring the implementation of a control system, the user must name, ordeclare, the variables used. This variable declar...

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    378SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageWhen declaring a variable, the user must specify the variable type in additionto the variable name. This allows the PLC to know what type...

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    379CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingEXAMPLE 10-1Implement the Boolean variable declaration (variable names andvariable types) for the input devices shown in Figure 10-2a for...

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    380SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageFigure 10-3. Boolean variable declaration.10-2 IEC 1131-3 PROGRAMMING LANGUAGESWhile the IEC 1131-3 programming standard provides great ...

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    381CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-4. Ladder diagram representation of a PLC program.FUNCTION BLOCK DIAGRAM (FBD)Function block diagram (FBD) is a graphical langu...

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    382SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming Languagevariable can be used throughout the program in other instructions and as acontrol output through the address mapping performed during var...

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    383CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingM1StopM1StartM1PL1PLC ProgramFigure 10-7. Ladder diagram equivalent of the circuit in Figure 10-6.MotorStopMotorStartMotorPilot_LightSTAR...

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    384SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageThe flexibility of custom block creation is enhanced by the fact that the usercan build custom blocks using ladder diagrams or any of the...

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    385CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-10. Example of the machine/assembly language used in microprocessors.Figure 10-11. Instruction list custom function block that ...

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    386SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageSTRUCTURED TEXT (ST)Structured text (ST) is a high-level language that allows structured pro-gramming, meaning that many complex tasks ca...

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    387CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFinishedConditionsto trigger reportCustom ReportFunction BlockTemp_VarPress_VarVariable_1ReportVariable_2Valuespassed fromvariablesIF REP...

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    388SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming Language123123LS_ReachIF Temp_1≥100PB_ReturnAction_2Action_3Figure 10-15. Transitions in a sequential function chart.the PLC to execute a certa...

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    389CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingoccurs (i.e., the limit switch LS_Reach triggers). After the PLC finishes action2, it will wait for transition 2 (IF Temp_1≥100) to occ...

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    390SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming Languageaction will occur until the At_Top_LS command is satisfied, at which time,the process will stop and the Return_Solenoid output will reset...

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    391CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingsteps, actions, and transitions. The actions represent the activation of thesolenoid and drill motor, while the transitions represent the...

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    392SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguagePROGRAMMING LANGUAGE NOTATIONOne of the greatest advantages of sequential function charts is that they areeasier to troubleshoot than sta...

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    393CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-19. Implementation of a simple program in (a) ladder diagram, (b) functionblock diagram, (c) structured text, and (d) instructi...

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    394SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageEXAMPLE 10-3In PLC applications, many limit switches exhibit a “bouncing” behav-ior (see Figure 10-21), meaning that the switch opens...

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    395CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-23. Timing diagram for a bouncing input signal.Figure 10-21. Bouncing behavior in a limit switch.Figure 10-22. Rough diagram of...

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    396SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageLS_BeforeTON 100AR 4000PR 4100LS_BeforeTON 101AR 4001PR 4100100Valid_LSL102L101Valid_LSU102ULSDelay_TimeConstantValid_LSDebounce FBDLS_Be...

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    397CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingalso be the debounced limit switch input (Valid_LS). The variableT_Delay will be an integer that is a preset time value of 50 msec. Thein...

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    398SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageSFC FORMATSequential function charts represent the order of events in a sequentialprocess. An SFC divides a process into many steps, whic...

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    399CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming12Start_BatchBatch_Complete1212(Start_Batch)(Batch_Complete)Batch_Time≥Timeout12Level:=Switch_LevelIf Level Then Motor:=TrueBatch_Time:...

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    400SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageEach step and transition in an SFC has an ON status or condition if it isactive and an OFF status if it is inactive. A dot, or token, ind...

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    401CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingEXAMPLE 10-4Figure 10-33 shows an SFC in three different stages: (a) step 3active, (b) step 4 active after being triggered by transition ...

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    402SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageTRANSITIONSAs described in the previous example, the triggering condition of a transitioncan be a momentary pulse that quickly goes from ...

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    403CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingbe combined with Boolean logic combinations (AND, OR, NOT) andIF...THEN instructions. For example, in Figure 10-37b, the control programi...

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    404SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageTransitions can also be logically combined with other instructions, mostcommonly with the structured text language. For instance, in Figu...

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    405CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingapplies for a normally closed device in a PLC using IEC 1131-3 program-ming—all normally closed devices should be programmed as normall...

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    406SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageFigure 10-41 illustrates a simple start/stop hardwired motor circuit and itstiming diagram. When the momentary normally open start push b...

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    407CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming101010StartStopX210Y110Motor10Y212Motor:=True12Start_AND_StopNOT_StopFigure 10-42. SFC implementation of the hardwired circuit in Figure ...

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    408SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageMotor_1, the logic takes into consideration that the normally closedstop push button is wired as normally closed. For Motor_2, the logics...

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    409CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingAs illustrated in Example 10-5, the programming of an input field devicedepends on how it is wired to the input interface. A timing diagr...

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    410SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageA divergence is when an SFC element has many links going out of it, whilea convergence is when an element has many links coming into it. ...

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    411CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingtions, so that the token advances in only one branch of the divergence.Therefore, if transition 1 is triggered, step 10 becomes active; i...

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    412SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageAND Divergences and Convergences. An AND divergence, also called adouble divergence, provides a link from one transition to many steps in...

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    413CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-54. AND convergence.because both steps 41 AND 51 will be deactivated by the transition. If morethan two links converge at the t...

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    414SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageSUBPROGRAMSMain ProgramSubprogramExecution of parent (main) programis suspended until subprogram ends.INOUTMainProgramChart 1MainProgramC...

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    415CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingwith the ability to have a main program with one or more subprogramsorganized in a “father-child” relationship (see Figure 10-58). A ...

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    416SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageWhen a program calls a subprogram, it asks for a value to be delivered whenexecution returns from the subprogram (see Figure 10-59). This...

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    417CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingST instructions with the instruction Init_Value:=SP_Check_Start initiatinga subprogram named SP_Check_Start. This subprogram calculates t...

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    418SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageAn action can also call a subprogram directly using an instruction syntaxthat is similar to a transition. For example, the following inst...

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    419CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingAn action in a sequential function chart is executed when its correspondingstep is active. When the step becomes active, the software con...

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    420SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageEXAMPLE 10-6Using SFC Boolean actions, implement a chart that will turn ON andOFF two pilot lights according to the timing diagram shown ...

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    421CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingSOLUTIONFigure 10-67 illustrates the desired timing diagram of the two inputs(Start and Reset) and the three pilot lights (PLight_1, PLig...

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    422SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageOR divergence. At the OR divergence, control goes to step 10(ON1_OFF2) if the Reset push button is not pressed (Not_Reset),thereby turnin...

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    423CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingshows this stand-alone configuration, along with an alternative set ofBoolean actions for this program. Although a stand-alone action is ...

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    424SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageFigure 10-73. Execution of a normal action.Figure 10-72. A count-up instruction implemented as a pulse action.123123CMDNOT_CMDCMD(Initial...

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    425CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming10111011(Normal_Action_Ex)Action (N):•••Instructions•••End_Action;Figure 10-74. Syntax for a normal action.1212Start_Counting...

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    426SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming Language101010Start_ CountingX2Stop_Counting10Cmd_Cnt10Last_Cmd10R_CountBeginning of 1st CountEnd of 1st CountR_Count = 1Beginning of 2nd CountEn...

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    427CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-77. Batching process implemented using SFC actions.xatnySnoitpircseD;)N(emaN_gorP_dlihCsiretemarap)N(nahtiwnoitcaCFSnA:lamroNro...

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    428SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageSFC actions may be started or killed using any of the programminglanguages, depending on the IEC 1131-3 software system manufacturer. The...

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    429CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingstart and kill of the Batch_Pump program are both pulse actions. The statusaction (step 10) is a nonstored action used to send a message,...

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    430SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageBoolean•NOT: Boolean negation• AND(&): logical AND•OR: logical OR•XOR: logical exclusive-OR•REDGE: rising-edge detection•...

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    431CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 10-5 continued.FUNCTION BLOCK DIAGRAM OPERATORS AND FUNCTIONSStandard OperatorsData manipulation• Assignment• Analog negationBo...

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    432SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguagePLC LANGUAGES SIMILAR TO THE IEC 1131-3PLC manufacturers may adapt their programmable controller languages toembrace some of the qualitie...

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    433CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 10-80. Pressing and stamping routine.Step 0Step 1Step 6Step 2Step 3Step 4Step 5(0) The machine is inactive(1) The operator presses...

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    434SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageFigure 10-81. Pressing/stamping routine programmed in (a) ladder diagrams and (b) RLLPlus. SG denotes a stage step and ISG denotes an ini...

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    435CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingReferring to Figure 10-81b, note that the program uses set and reset outputinstructions (SG2 and SG4, respectively) to turn ON and OFF th...

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    436SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageFigure 10-83. (a) An SFC program for the press/stamp control program and (b) itscorresponding flowchart.(a)(b)PartPresent?PartLocked?012P...

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    437CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingEXAMPLE 10-8Referencing Figures 10-81b and 10-83a, implement an additionalstage that monitors a normally closed stop push button and rese...

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    438SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming Languageit also scans the Stop signal, which if pressed, resets all outputs (Y0to Y2) and stages (S0 to S6) and then jumps to the initial stage (...

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    439CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe IEC 1131-3 standard provides PLC users with tremendous advantagesin both the programming and troubleshooting of a control system. Alt...

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    440SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER10The IEC 1131 Standard andProgramming LanguageactionBoolean actionBoolean variableconvergencedivergencefunction block diagram (FBD)IEC 1131 standardIEC 1131-3 programming standardinst...

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    441CHAPTER10The IEC 1131 Standard andProgramming LanguageIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingsequential function charts (SFC)SFC actionstand-alone actionstepstructured text (ST)subprogramtransition

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    SYSTEM PROGRAMMINGAND IMPLEMENTATIONCHAPTERELEVENHe that invents a machine augments thepower of man and the well-being of mankind.—Henry Ward BeecherIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    444SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationThe implementation of a control program requires complex organizationaland analytical skills, which change depending on the application. Becauseth...

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    445CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingcertain tasks in our daily lives. The procedure that a person follows to gofrom home to either school or work is an algorithm—the person exits t...

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    446SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationAs mentioned previously, understanding the process or machine operationis the first step in a systematic approach to solving the control problem. ...

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    447CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming(hardware and software), and understand the PLC system. Once thesepreliminary details are understood, the programmer can begin sketching thecontro...

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    448SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationthrough a flowchart. Even the flowchart symbols themselves have specificmeanings, which aid in the interpretation of the solution algorithm. Figur...

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    449CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-4. (a) PLC contact symbology and (b) logic gate representation of a logicsequence.Figure 11-5. A combination of logic gates and contact ...

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    450SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationCONFIGURING THE PLC SYSTEMTable 11-2. I/O address assignment table for real inputs and outputs.sserddAO/IeludoMepyTkcaRpuorGlanimreTnoitpircseDtup...

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    451CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingEXAMPLE 11-1For the circuit shown in Figure 11-7, (a) identify the real inputs andoutputs by circling each, (b) assign the I/O addresses, (c) assi...

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    452SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationAssume that the PLC used has a modularity of 8 points per module.Each rack has 8 module slots, and the master rack is number 0. Inputsand outputs ...

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    453CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-8. Identification of real I/O (circled).Table 11-4. I/O address assignment.sserddAO/IeludoMepyTkcaRpuorGlanimreTnoitpircseDtupnI0001BPtr...

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    454SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementation(c) Table 11-5 presents the output assignments, including a descrip-tion of each internal. Note that control relay CR2 is not assigned asan intern...

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    455CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingREGISTER ADDRESS ASSIGNMENTThe assignment of addresses to the registers used in the control program isanother important aspect of PLC organization...

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    456SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-10. Hardwired components in a PLC system.opens when the PLC is first turned on. As shown in Figure 11-10, thesecontacts are connected in...

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    457CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramminglocation, since remote systems also have fault contacts incorporated into theremote controllers. This allows subsystem failures to be signaled pro...

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    458SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-12. PLC ladder diagram of the circuit in Figure 11-11.Master Control Relays. Another circuit the programmer should be awareof is a maste...

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    459CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingelements from line 3, where the MCR contact is located, to the last elementin line 51. If the master control relay is ON, power will flow to these...

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    460SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationinstruction ends the MCR fence. The instructions corresponding to thehardwired circuits that branch from line 2 in the electromechanical diagramof...

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    461CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-16. MCR-controlled program elements.EXAMPLE 11-3Highlight the sections of the circuit in Figure 11-15 that will be underthe control of a...

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    462SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationmust include two internal control relays that take SOL1 out of the fence.Figure 11-18 illustrates the fenced circuit with the additional internals...

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    463CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingBidirectional Power Flow. The circuit in Figure 11-19 illustrates anothercondition that can cause programming problems: the possibility of bidirec...

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    464SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationthat closes or opens once the timer is enabled), the programmer must use aninternal output to trap the timer, then use the internal’s contact as...

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    465CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingthe previous stages (control task definition, I/O assignment, etc.) have beendone. Figure 11-21 shows a sample program code generated from logic g...

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    466SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationCONTROL PROGRAMMING AND PLC DESCRIPTIONSFigure 11-22. Example PLC configuration.The PLC can accept four-channel analog input modules, which can be...

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    467CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingPoint addresses 10008 to 27778 may be used for internal outputs, and registerstorage starts at register 30008 and ends at register 47778. Two type...

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    468SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationrung. If the instantaneous TMR1 contacts are implemented using a PLC time-delay contact, then PB1 must be pushed for the timer’s required time p...

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    469CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingSIMPLE START/STOP MOTOR CIRCUITFigure 11-24. PLC implementation of the circuit in Figure 11-23.Figure 11-25 shows the wiring diagram for a three-p...

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    470SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationconnections. Table 11-11 shows the I/O address assignment, which uses thesame addressing scheme as the circuit diagram (i.e., inputs: addresses 00...

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    471CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 11-11. I/O address assignment.Figure 11-27. PLC implementation of the circuit in Figure 11-25.(a normally open PLC contact) in series with t...

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    472SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-28. PLC wiring diagram of a three-phase motor.Figure 11-29. Motor control circuit’s wiring diagram.Motor32T1T2T3L1L2L3MOLPLCOutput030F...

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    473CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-29, the starter’s seal-in contacts (labeled as 3—| |—2) are not usedand are shown as unconnected. If the motor is running and the...

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    474SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationshould include the use of the overload contacts to monitor the occurrence ofan overload condition. The auxiliary starter contacts (M1 and M2) are ...

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    475CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingoutput devices—the forward and reverse starters and their respective inter-locking auxiliary contacts—have addresses 030 and 032. The forward ...

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    476SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationTable 11-12. I/O address assignment.Figure 11-34. PLC implementation of the circuit in Figure 11-31.sserddAO/IeludoMepyTkcaRpuorGlanimreTnoitpircs...

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    477CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingto the overload. An additional normally open acknowledge overload resetpush button, which is connected to the input module, allows the operator to...

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    478SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-36. (a) Hardwired relay circuit and (b) wiring diagram of a reduced-voltage-start motor.Figure 11-37 illustrates the hardwired circuit w...

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    479CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 11-13. I/O address assignment.Table 11-14. Internal address assignment.Table 11-15. Register assignment.Figure 11-37. Real inputs and output...

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    480SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationgrammed as normally open (closed when the overloads are closed and themotor is running) and placed in series with contact 1000 in line 3 of the PL...

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    481CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-39. Operator station for a variable speed drive.Table 11-16 shows the I/O address assignment table for this example, whileFigure 11-40 i...

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    482SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-40. Connection diagram from the PLC to the VS drive’s terminal block.Table 11-16. I/O address assignment.sserddAO/IeludoMepyTkcaRpuorG...

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    483CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingbecause the drive’s CR1 contact will not receive power from the outputmodule. This configuration, however, does not provide low-voltage protec-t...

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    484SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationthat the start, stop, run/jog, potentiometer, and forward/reverse field devicesshown are from the operator station. These devices are connected to...

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    485CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 11-18. Internal output assignment.Table 11-19. Register assignment.Figure 11-43. Bottle-filling system.Table 11-17. I/O address assignment.e...

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    486SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-44 illustrates the PLC ladder implementation of the bottle-fillingapplication. Once the start push button is pushed, the outfeed motor (...

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    487CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingLARGE RELAY SYSTEM MODERNIZATIONThis example presents the modernization of a machine control system thatwill be changed from hardwired relay logic...

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    488SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-45. Electromechanical relay diagram.PB1MasterStartPB2MasterStopPB5 SetupPB6 ResetPB3EmergencyStop 1PB4EmergencyStop 2M1 SCR1-1SCR1-2MCRO...

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    489CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-46. Elements of the moderization example system to be left hardwired.Table 11-20. I/O address assignment.sserddAO/IeludoMepyTkcaRpuorGla...

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    490SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementation1700 accomplishes this same function (for this example, MCR1700 is thefirst available address for MCRs). If the MCR coil is not energized, the PLC...

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    491CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-47. PLC implementation of the circuit in Figure 11-45.L1L1L2L2PB5PB6*PS1000001InputsProgram CodingOutputs002003004SS1SS2PL2030PL3031PL40...

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    492SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationtimer will not seal until it has timed out. If PB6 is released, the timer will resetbecause PB6 is not sealed. To solve this problem, we can use i...

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    493CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-49. Relationship between counts and degrees Celsuis.Figure 11-50. Flowchart of process steps.diagram of the elements used in this system...

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    494SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-51. Subroutine flowcharts: (a) check for correct range and (b) linearize to °C.Tables 11-22 and 11-23 present the register and internal...

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    495CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 11-24. I/O address assignment.Table 11-23. Internal output assignment.eciveDlanretnInoitpircseD—0001)daeRSWT(delbane)XUM(SWTnirefX—1001)...

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    496SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-52. PLC implementation of the analog input comparison system.Start000XFER INTWS Read1000Slot 1Rack 0Length 2Reg 4000TWS Read1000BCD-BINB...

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    497CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-53. Subroutine 1100—check for valid TWS range and convert to decimal.Figure 11-54. Subroutine 1200—convert analog counts to degrees....

  • Page 510

    498SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationThe check range subroutine compares the values entered for the low and hightemperature alarms with the constants 100 and 850. If the values are wi...

  • Page 511

    499CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingWhen the start push button starts the machine, the moving piece must moveto the virtual starting position (V.P.) defined by the set of 4-digit TWS...

  • Page 512

    500SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationTable 11-25. I/O address assignment.Table 11-26. Register assignment.Subroutines are used to implement the flowchart, to facilitate interlockingan...

  • Page 513

    501CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 11-27. Internal output assignment.Figures 11-58, 11-59, and 11-60 present the subroutine codes. In Figure 11-58 (check for 0-inch position),...

  • Page 514

    502SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-57. PLC implementation of the LVDT analog position reading example.XFER INLVDT Read1001Rack 0Slot 7Reg 4100Length 1Start000Start Mach100...

  • Page 515

    503CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-59. Subroutine 1250 moves the part to the virtual position.Figure 11-58. Subroutine 1150 brings moving part to 0" position.XFER INR...

  • Page 516

    504SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-60. Subroutine 1350 returns the part to the virtual position at the end of cycle.Behind V.P.1353≤Ahead of V.P.1351≥Return to V.P.135...

  • Page 517

    505CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingIn Figure 11-59, scale multiplication allows the virtual position, which hastwo decimal points (10–2) to be multiplied by the multiplication con...

  • Page 518

    506SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationTo provide an example of this type of application, we will use a system witha pressure transducer that provides a 0 to +10 VDC output. The range o...

  • Page 519

    507CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-62. (a) Linear behavior and (b) actual nonlinear measurements.Table 11-28. Sample psi measurements and corresponding counts.tnemerusaeMi...

  • Page 520

    508SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-63. (a) Main program look-up procedure and (b) interpolation subroutine.Table 11-30 shows the register assignment table for this example...

  • Page 521

    509CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 11-31. Internal output assignment.Figure 11-64 shows the method used to interpolate psi values based on thecontents of each register used. T...

  • Page 522

    510SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-64. Interpolation method.Figure 11-65. Main program.(psi)4450 points to high psi4150 holds computed psi4400 points to low psiCountspsiRe...

  • Page 523

    511CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-66. Interpolation subroutine.(continued at right) High Cts ≥ input Cts1102 Subroutine1100 High Cts ≥ Input Cts 1102Fo...

  • Page 524

    512SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationLARGE BATCHING CONTROL APPLICATIONThis example explains the automation of a large batching process. Itincludes the process description, controller...

  • Page 525

    513CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingingredient B by opening SOL2. LLS2 detects the quantity of ingredient B,which should be 400 gallons. The temperature should be at 100°C ± 10%dur...

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    514SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-68. Flowchart for the large batching application process.STARTBack To StartYesYesNoNoNoCheck ForInitialConditionsFinishIngredients?AllCo...

  • Page 527

    515CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-69. Logic diagrams for the batching application.Start PBMixMotorStart MixStart MixTempOK 1EmptyStop PBSOL3Tank In PosPL1PL4PL5PL3PL2Star...

  • Page 528

    516SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationIn logic diagram 4, the Ready to Add A signal enables SOL1 to open. Thisaction occurs while LLS1 is still open (less than 100 gallons) and the dra...

  • Page 529

    517CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingThe assignment of real I/O begins by addressing the real inputs and outputs.Table 11-32 illustrates the assignment of I/O for this application exa...

  • Page 530

    518SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationand low. I/O register 3034 stores the analog value of the temperature. Thisregister will be compared to the storage registers that hold the equiva...

  • Page 531

    519CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-71. PLC implementation of the batching application.(continued on next page)L1L1L2L2StartStopTank inPositon000001InputsProgram CodingOutp...

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    520SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-71 continued.(continued on next page)Mix CMD1013SOL2016Valve 2 Open PL017Fin A015LLS2005SOL3023 SOL2016Valve 2 OpenFinish Ingr. B016S...

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    521CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming11-7 SHORT PROGRAMMING EXAMPLESFigure 11-71 continued.EXAMPLE 1: INTERNAL STORAGE BITSThis section presents several examples of logic series tha...

  • Page 534

    522SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-72. (a) A relay circuit using seven rungs that is (b) converted to five rungsusing an internal.only allowed five OR branches, an interna...

  • Page 535

    523CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-73. Start/stop circuit.Figure 11-74. Exclusive-OR circuit.open) is a momentary device (i.e., it allows continuity only when pressed), ac...

  • Page 536

    524SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand Implementationwhich stays ON for one scan and then goes OFF. The signal remains OFFuntil the trigger is activated, causing it to come ON again. Clear or resetsi...

  • Page 537

    525CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-77. Initialization circuit using an MCR.EXAMPLE 7: SYSTEM START-UP HORNA start-up horn logic circuit (see Figure 11-78) is used to sign...

  • Page 538

    526SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationEXAMPLE 8: OSCILLATOR CIRCUITAn oscillator logic circuit (see Figure 11-79) is a simple timing circuit thatgenerates a periodic output pulse of a...

  • Page 539

    527CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-80. Annunciator flasher circuit.EXAMPLE 10: SELF-RESETTING TIMERThe self-resetting timer shown in Figure 11-81 provides a one-scan puls...

  • Page 540

    528SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationEXAMPLE 12: SEQUENTIAL MOTOR STARTINGThis example (see Figure 11-83) illustrates how several motors or otherdevices can be started sequentially, ...

  • Page 541

    529CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingEXAMPLE 13: DELAYED DE-ENERGIZE DEVICEThis example (see Figure 11-84) illustrates the use of an OFF-delay timer tode-energize a motor or another ...

  • Page 542

    530SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationEXAMPLE 14: 24-HOUR CLOCKA 24-hour clock has many applications, but it is typically used to display thetime of day or to determine the time a rep...

  • Page 543

    531CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 11-85. 24-hour clock circuit.Figure 11-86. (a) Hardwired circuit allowing bidirectional power flow at CR3 and(b) reconfiguration to elimina...

  • Page 544

    532SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER11System Programmingand ImplementationFigure 11-87. Binary counting program.EXAMPLE 16: EXCEEDING THE MAXIMUM COUNTSome applications require the capability to count events that will e...

  • Page 545

    533CHAPTER11System Programmingand ImplementationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingcontrol strategycontrol taskflowchartingprogram codingFigure 11-88. (a) A push-to-start/push-to-stop circuit and (b) its timing diagram.KEYTERMSEX...

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  • Page 547

    PLC SYSTEMDOCUMENTATIONCHAPTERTWELVEIf you cannot—in the long run—tell everyonewhat you have been doing, your doing hasbeen worthless.—Erwin SchroedingerIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 548

    536SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationWhile proper PLC programming is important for a well-run applicationprogram, all of that work is lost without adequate system documentation.Without documentati...

  • Page 549

    537CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingTable 12-1. Components of a good PLC documentation package.12-2 STEPS FOR DOCUMENTATIONSYSTEM ABSTRACTA good system design starts with a thorough understandin...

  • Page 550

    538SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationprogrammable controller will gather data about total production from bothlines and report it in printed form at the end of each shift. Finally, the statementof...

  • Page 551

    539CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 12-2. System arrangement diagram.specific I/O devices. For example, during start-up the user can easilydetermine that I/O point 0200 (LS, PB, etc.), loc...

  • Page 552

    540SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationFigure 12-3. System configuration diagram of a PLC interfacing with process bus and device bus networks.01234567012345670123456701234567ControlValveControlValv...

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    541CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 12-4. I/O wiring connection diagrams for (a) inputs and (b) outputs.12-4 illustrates an example of an I/O wiring connection diagram. Thisdiagram shows t...

  • Page 554

    542SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationI/O ADDRESS ASSIGNMENTSTable 12-2. I/O address assignment.INTERNAL STORAGE ADDRESS ASSIGNMENTSAn internal storage address assignment document is an important p...

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    543CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingSTORAGE REGISTER ASSIGNMENTSTable 12-3. Internal storage address assignment.Each available system register, whether a user storage register or an I/Oregister, ...

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    544SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationstorage address assignments requires that the devices connected to the PLCvia its I/O be declared, or defined, as variables. Table 12-5 illustrates a typicalva...

  • Page 557

    545CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 12-7 illustrates a ladder control program with generic documentedelements in the ladder rung. Sometimes, only the I/O address numberrepresents these lad...

  • Page 558

    546SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationMost IEC 1131 software systems include a documentation package that usesthe defined variables as the labels for the programmed control elements.These systems a...

  • Page 559

    547CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgrammingFigure 12-8. IEC 1131 level 1 chart printout.CONTROL PROGRAM STORAGEFor the most part, PLC programming occurs at a location other than wherethe controller will...

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    548SECTION3PLCProgrammingIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER12PLC SystemDocumentationhand, several manufacturers in the PLC support industry have developedsophisticated, yet simple, systems for documenting a total PLC system. Thesesystems speed...

  • Page 561

    549CHAPTER12PLC SystemDocumentationIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION3PLCProgramming12-4 CONCLUSIONMuch can be said about documentation and its relevance to the total systempackage. We cannot overemphasize the importance of establishing—fro...

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

  • Page 563

    PLC PROCESSAPPLICATIONSSECTION FOUR•Data Measurements and Transducers•Process Responses and Transfer Functions•Process Controllers and Loop TuningIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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  • Page 565

    DATA MEASUREMENTSAND TRANSDUCERSCHAPTERTHIRTEENWhen you measure what you are speaking aboutand express it in numbers, you know somethingabout it; but when you cannot measure it, whenyou cannot express it in numbers, your knowl-edge is of a meager and unsatisfactory kind.—William Thomson, Lord K...

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    554SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersCHAPTERHIGHLIGHTSAs in any technical discipline, PLC users must know how to use and applythe measurement instruments and equipment that are c...

  • Page 567

    555CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsXXXXXnXXnnnni=+++…= =∑1231 orTherefore, at the new reporting time, the instrument will emit a 14.6 mVsignal—the mean value of the five ...

  • Page 568

    556SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand Transducersread as 20 mV due to noise in the system, the mean would have increased to15.8 mV, whereas the median would have remained 14.7 mV. Thus, them...

  • Page 569

    557CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsare from the mean. For our instrument readings, the standard deviation willhave a value of σ = 5.26:σ =++++−==31 3626 01 0 1626 01 27 045...

  • Page 570

    558SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-2. Distribution of data values as a function of standard deviation.MEASUREMENT ERRORSThe possibility of measurement errors is prese...

  • Page 571

    559CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsTable 13-1. Measurement error types and their causes.srorrEssorGsrorrEmetsySsrorrEmodnaRelbissoPsesuaCelacstcerrocninagnisusgnidaeR•sgnidae...

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    560SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand Transducers13-2 INTERPRETING ERRORS IN MEASUREMENTSThe discovery of errors is invaluable when controlling a machine or processbecause error information...

  • Page 573

    561CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsand their average weights are AB and , then the final weight of a mixcontaining both materials would be AB+. This outcome is the addition ofb...

  • Page 574

    562SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersEXAMPLE 13-1A manufacturing plant produces sphere-shaped pellets. These pel-lets are heated for a period of time to make specific changes in ...

  • Page 575

    563CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsSOLUTION(a) The total weight (Wt) of the sphere can be calculated as volumetimes weight (V x W):VrWVWrWt===433433ππTherefore, the final tot...

  • Page 576

    564SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersEXAMPLE 13-2An electric heater with a current control system has a resistance valueof 150 ohms. The resistor has a guarantee deviation of ±0...

  • Page 577

    565CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsIR=±=±=±=±45150. amps0.1%4.50.0045 ampsohms0.15%1500.225 ohmsThe variations in power, ∆PI and ∆PR (power variations due to currentan...

  • Page 578

    566SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersBRIDGE CIRCUIT TECHNIQUESBridge circuits use resistive elements to sense measurement changes.Depending on how the circuit is configured, the ...

  • Page 579

    567CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 13-4. Voltage-sensitive bridge circuit.SOLUTION(a) Assuming that RD = ∞ (i.e., it is very large) and the excitation voltageimpedance...

  • Page 580

    568SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersTherefore, the bridge resistance ratio is:RRRR1234=where R4 is the measuring resistance element.Current-Sensitive Bridge. A current-sensitive...

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    569CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 13-5. Bridge circuit.∆ΩΩΩRRRB44410111=−=−= K K KThe current measurement is defined by (values of R in KΩ):IVRRRRRRRDiBDB...

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    570SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-6. (a) Cutaway and (b) diagram of an LVDT.Table 13-2. Transducers that use LVDT mechanisms.recudsnarTstnemerusaeMdnasesUllecdaoLgni...

  • Page 583

    571CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsModern LVDTs provide demodulation, or rectification, circuits to convertthe secondary output into a DC voltage signal. This voltage signal is...

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    572SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersEXAMPLE 13-5Graphically illustrate the position of an LVDT core that has a totaldisplacement range of 20 inches and an output of ±10 VDC.Fig...

  • Page 585

    573CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsThere are many types of thermal transducers in the marketplace; however, thissection only discusses the most commonly used ones: resistance t...

  • Page 586

    574SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-11. RTD in a bridge circuit.Figure 13-12 presents a typical wire compensation method used to balancelead wire resistance. The lead ...

  • Page 587

    575CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsAs mentioned previously, the changes in RTD resistance are proportional tochanges in temperature. The following equation defines these resist...

  • Page 588

    576SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand Transducersresistance of a thermistor decreases; therefore, a thermistor is said to have anegative temperature coefficient. Although most thermistors ha...

  • Page 589

    577CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsTable 13-4. Advantages and disadvantages of thermistor types.Figure 13-14. Temperature-versus-resistance curve (RT/R @ 25°C).Courtesy of The...

  • Page 590

    578SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersRTD for certain temperature ranges. Therefore, thermistors provide moreaccurate readings when the span of measurement is narrow. For example,...

  • Page 591

    579CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsEXAMPLE 13-6A thermistor has a resistance value of 100 KΩ at 3°C and a β constantof 3900°K. At what temperature (°C) will the thermisto...

  • Page 592

    580SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand Transducersphenomenon known as the Seebeck effect. Temperature T1, the hot junction,is the temperature being measured, while T2, the cold junction, is t...

  • Page 593

    581CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsTable 13-6. Thermocouple comparisons.(From the Instrument Engineer’s Handbook: Process Measurement)epyTASInoitangiseDevitisoPeriWevitageNer...

  • Page 594

    582SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersEXAMPLE 13-7A Chromel-Constantan (type-E) thermocouple has a reading of 16.42mV at its output. The reference junction is at 46°F (see Figure...

  • Page 595

    583CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsThe value 0.458 mV is an offset value that must be added to thethermocouple output value to compensate for the cold junction read-ing. Theref...

  • Page 596

    584SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-19 shows how thermocouples are connected using lead wires.Optimally, the lead wires should be made of the same material as thetherm...

  • Page 597

    585CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsmust be isolated from each other to avoid thermal reaction among them, aswell as to avoid a thermocouple emf short. The reference cold juncti...

  • Page 598

    586SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersEXAMPLE 13-8Three type-B thermocouples, which are connected in a thermopileconfiguration, will be connected to a thermocouple input module in...

  • Page 599

    587CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsLVDTSAs mentioned previously, LVDTs (linear variable differential transformers)operate on the principle of a movable core inside a wound coil...

  • Page 600

    588SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersPotentiometer transducers are prone to problems such as excess friction inthe wiper arm, limited resolution in the wire-wound unit, and mecha...

  • Page 601

    589CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsChanges in temperature affect strain gauge circuits, so these circuits requiretemperature compensation. A dummy gauge, added to the bridge-co...

  • Page 602

    590SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-26 illustrates the most commonly used type of Bourdon tube, theC-tube. The pressure inlet end of the tube is fixed, while the other...

  • Page 603

    591CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsLOAD CELLSLoad cells are force or weight transducers based on a direct application ofbonded strain gauges. These devices measure deformations...

  • Page 604

    592SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersEXAMPLE 13-9A conveyor transports material that is weighed on a platform 2meters in length. A load cell, which is connected to an analog inpu...

  • Page 605

    593CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsorifice plates. One of the most common fluid flow transducers for detectingfluid motion is the turbine flow meter. This transducer transforms...

  • Page 606

    594SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-29. Venturi tube diagram and the pressure and velocity at points P1 and P2.Figure 13-30. Orifice plate flow transducer.PressureVelo...

  • Page 607

    595CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsThe constant k takes into account the density of the fluid, the ratio of pipe toobstruction at cross-sectional points P1 and P2, temperature,...

  • Page 608

    596SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersSOLUTIONTo implement the ratio control of products B and C at the specifiedpercentage of product A (wild flow), we must read the differential...

  • Page 609

    597CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationswhere KA, KB, and KC are the given constants. The square root valueof the analog input ∆P should be taken after the input count valuecorres...

  • Page 610

    598SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersSOLUTIONThe flow rate of the fluid is described by :QVA=where:QVA=== the flow rate the velocity of the flow the cross - sectional area of the...

  • Page 611

    599CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplications13-8 VIBRATION TRANSDUCERSVibration transducers are used in system applications that require thedetection of vibration, which can severely d...

  • Page 612

    600SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersThe angular frequency can also be expressed as angular velocity where ω =2πf. In vibration, velocity is the first derivative of displacemen...

  • Page 613

    601CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsAll three vibration terms—displacement, velocity, and acceleration—havethe same periodic frequency. Another important term in vibration m...

  • Page 614

    602SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersTable 13-10. Vibration identification guide.(Courtesy of PMC/BETA Corp., Natick, MA)esuaCotevitaleRycneuqerFmprenihcaMebortS-esahPerutciPedut...

  • Page 615

    603CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsThis system has a period (T) equal to:fTTf====11180 125Hz.sec(b) The peak acceleration is:asfspeakm/sec=====ωππ22222228 0 0150 265 0 0125 ...

  • Page 616

    604SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand Transducerselectrical output (voltage or current) proportional to the acceleration of thevibration. A piezoelectric transducer does this using a piezoel...

  • Page 617

    605CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 13-38. Vibration warning level guide.(Courtesy of PMC/BETA LP, Natick, MA)1.00.50.10.050Velocity (inches/sec)0.20.30.20.20.40.20.40.30...

  • Page 618

    606SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand TransducersFigure 13-39. Vibration severity chart.(Courtesy of PMC/BETA LP, Natick, MA)120.80.60.50.40.30.20.020.01Velocity LimitsVery RoughDanger ofoil...

  • Page 619

    607CHAPTER13Data Measurementsand TransducersIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationssmooth to very rough severity and indicates possible consequences (boldblue lines indicating very bad, bad, fair, etc.). For machines with hi...

  • Page 620

    608SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER13Data Measurementsand Transducerstransmitter combination can also be interfaced with a programmable control-ler to monitor vibration. The internal contacts of the transmitter...

  • Page 621

    PROCESS RESPONSES ANDTRANSFER FUNCTIONSCHAPTERFOURTEENMathematics may be defined as the subject inwhich we never know what we are talkingabout, nor whether what we are saying is true.—Bertrand RussellIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 622

    610SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsAs we have already discussed, PLCs control machines and processes viadiscrete, analog, and special I/O interfaces that communicate wit...

  • Page 623

    611CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsHcE = SP – PVCVSP +–ΣSteamTemperatureSensorProduct DischargeWaterMaterial 1 Material 2Figure 14-1. Reactor tank control system.Fi...

  • Page 624

    612SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-4. Control system block diagram including I/O interfaces.E = SP – PVCVSP +–ΣSteamProduct DischargeWaterMaterial 1Materi...

  • Page 625

    613CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-5. Control system using a PID interface.Figure 14-6. A control loop with a disturbance.Figure 14-7. Cruise control process l...

  • Page 626

    614SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-8. Cruise control compensation graphs showing (a) the set point speed, (b) thereaction of the process variable to the distur...

  • Page 627

    615CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-9. (a) Positive and (b) negative feedback.This equation can also be represented as:EPVSP=−where the set point is subtracte...

  • Page 628

    616SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsINTERPRETATION OF ERRORThe representation of error as the difference between the set point and theprocess variable provides a “natur...

  • Page 629

    617CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-10. Error as a percentage of the process variable range.Figure 14-11. Process control loop for Example 14-1 given (a) a 100...

  • Page 630

    618SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFor a process variable range of 100 to 200°C, the error is:E%.%=°−°°−°=°−°=−=−1801681002001210001212CCCCCC(b) For a p...

  • Page 631

    619CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-12. Process regulated by an I/P converter.AnalogOutputModuleSteamI/P ConverterTo ReactorTankEXAMPLE 14-2The PLC system shown...

  • Page 632

    620SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-14. Minimum temperature output of 20°C corresponding to a 1 Vcontrol variable output.Figure 14-13. Relationship between con...

  • Page 633

    621CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsCV%...%====64641006464 V – 0 V10 V – 0 VHaving a minimum control output value that is greater than zero iscommon in many process c...

  • Page 634

    622SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionslortnoCelbairaVgnitcAtceriDgnitcAesreveRrorrErorrE↑↑↑↓↓↓Table 14-1. Relationship between error and the control variable in...

  • Page 635

    623CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-17. (a) Control loop process variable, (b) timer for upper limit alarm, (c) timerfor lower limit alarm, and (d) alarm activa...

  • Page 636

    624SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-18. Process change due to (a) a change in set point and (b) a disturbance.to the behavior of the process when the error is z...

  • Page 637

    625CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-19. Transfer function.ControllerProcessESPCVPVPV+–ΣHc =HcHpCVEHp = PVCVFigure 14-20. A closed-loop control system with t...

  • Page 638

    626SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsCVPVSteamInSteamReturnHot Water OutCold Water InTemperatureTransmitterTTFigure 14-21. Hot-water heater system.Figure 14-22. Water heat...

  • Page 639

    627CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-23. (a) Control variable step change and (b) its corresponding processvariable change.0%55%100%CVt75%20% input change15°C65...

  • Page 640

    628SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-24. Process gain in the hot-water tank example.CVPVSteamInSteamReturnConstant OutputFlow (Qout)Cold Water InConstantMass of ...

  • Page 641

    629CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsProcessPVCVBAt0BAt0HpHp == 1PVCVFigure 14-25. Instantaneous response of the process output to a step change in input.Figure 14-26. Dea...

  • Page 642

    630SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-28. Sensor dead time delay.tdPVPVTo ControllerTTTemperatureTransmitterSensorTemperature °CChangeOccursDead TimeDelayTempCha...

  • Page 643

    631CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-29. Lag time in a car’s cruise control mechanism.SP70 mphCVAcceleratortt0t1DisengageResumeLagLag55 mph70 mph55 mphPVSpeedt...

  • Page 644

    632SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-30. First- and second-order lags.Figure 14-31. Transfer functions in a control system.Mathematically, transfer functions are...

  • Page 645

    633CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsmathematical derivation of Laplace transforms. However, we will discusshow they are used in process control functions, to aid in the u...

  • Page 646

    634SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFirst-Order EquationsDESCRIPTIONAny Function fUnit Step InputStep InputDelay (Dead Time) toStep InputFirst-Order ResponseFirst-Order R...

  • Page 647

    635CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsDESCRIPTIONLAPLACETRANSFORMTIMEFUNCTIONFirst-Order Response to StepInput (A1 /s) with Lag AAet121()−− τ A1A2s(τs+1) ...

  • Page 648

    636SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsTable 14-3. Derivative Laplace transforms.InputOutputHpY(s)X(s)ProcessFigure 14-32. Process inputs and outputs in Laplace form.order d...

  • Page 649

    637CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsThis indicates that the Laplace output X(s) is equal to the Laplace input timesthe transfer function in Laplace form:XYsss()()=+...

  • Page 650

    638SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-33. R/C electrical network diagram.EXAMPLE 14-3Figure 14-33 represents an R/C (resistor/capacitor) electrical network.Find (...

  • Page 651

    639CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsVCidtCVVRdtCVRdtCVRdtRCVdtRCVdtRCVdtV dtttinttttttoutinoutoutinoutinout ==−()=−=−=−∫∫∫∫∫∫∫...

  • Page 652

    640SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-34. Block diagram of the R/C network.Referring to the hot-water heater example used in Section 14-3, let’s assumethat the ...

  • Page 653

    641CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-35. Integral transfer function.Previously, we calculated experimentally that the gain for this process is0.8°C/% and that i...

  • Page 654

    642SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsPVAsCVss()()= An integral process integrates the input with the process over time. Thisimplies that the rate of change of ...

  • Page 655

    643CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-36. Integral response to a step change.Figure 14-37. PID process control loop.CVCVBt (sec or min)PVIntegralProcess ∫A dtP...

  • Page 656

    644SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsCVK EKEdtKdEdtCVtPItDt()()=+++∫=00where:CVKESPPVKKtPID())==−== the control variable output the proportional gain= the error ( the ...

  • Page 657

    645CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-38. Transfer function of a system with dead time.A yields an output of magnitude A. The output, however, has a dead timeequa...

  • Page 658

    646SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-39. First- and second-order lags.First-OrderProcessSecond-OrderProcessPVCVPVCVττ1τ2FIRST-ORDER LAG RESPONSESFirst-order l...

  • Page 659

    647CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-40. First-order lag process response.Figure 14-41. First-order transfer function with lag in the Laplace domain.VVeVeVeVVtou...

  • Page 660

    648SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsOuttt0Process transfer function [Hp(t)]A1τA1ττe–t0.368t = τFigure 14-42. Process transfer function in the time domain.Using Tabl...

  • Page 661

    649CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsOuttt0t = τStep Input1 – e10.6320.368First-Order Responseto Step Input(Process)τe–tτ–tFigure 14-43. Process variable’s lag ...

  • Page 662

    650SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsEXAMPLE 14-4A process system has a first-order response with a time constant of10.8 minutes. (a) Calculate how long it will take for t...

  • Page 663

    651CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-45. Second-order response to a step input.SECOND-ORDER LAG RESPONSESA second-order lag response exhibits oscillations that o...

  • Page 664

    652SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-46. Damping coefficient effect on the oscillation of a second-order response.Figure 14-47. Sinusoidal response of a second-o...

  • Page 665

    653CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplications2πωn1fnorFigure 14-48. Response period of a sinusoidal curve.Solving for ωn yields:ωπnnf= 2So, the radian/sec frequency term ωn ...

  • Page 666

    654SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsEXAMPLE 14-5For an overdamped system (ζ > 1), solve for (a) Ksys, (b) ωn, (c) τsys,and (d) ζ using the transfer functions for a...

  • Page 667

    655CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplications sysK678 2ζωn123 ωn2{HpAAssAAsss()()()()=++=+++[]12121212212111ττττττDividing by the term τ1...

  • Page 668

    656SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer Functions(c) Earlier, we explained that τsys is equal to 1 over the frequency ωn.Using the information from part (b), τsys for an overdampe...

  • Page 669

    657CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-50. Real-time transfer function of an overdamped second-order process.tH(t) = (e – e )Gain KOD = AHAτ1– τ232.750....

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    658SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-52. A heavily damped response.constants is significantly longer than the other (i.e., τ1 >> τ2). Figure 14-52illustr...

  • Page 671

    659CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-53. Two first-order systems with different lag times cascaded to form anoverdamped second-order system.OutInInOutH(s)1H(s)2H...

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    660SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsEXAMPLE 14-6Show (a) how to derive the second-order critically damped transferfunction from the second-order lag transfer function and...

  • Page 673

    661CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplications(b) From Example 14-4, we know that:ττ τζττττsys2==+121212Because τ1 = τ2 in a critically damped system, τsys becomes:ττ...

  • Page 674

    662SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsThe inverse Laplace transform of a second-order critically damped system’sresponse to a unit step, given that the gain Ksys equals A...

  • Page 675

    663CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsFigure 14-55. Underdamped response.Figure 14-56. Frequency of oscillation is (a) lower when ζ is closer to 1 and (b) higherwhen ζ ...

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    664SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsFigure 14-57. Parameters of an underdamped second-order system.τζωsys =1nwhich indicates that the lag time constant depends on the ...

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    665CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsτζωζωτsyssysor==11nnThe response of a first-order exponential system is et−τ , where τ is thesystem’s time constant. There...

  • Page 678

    666SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer FunctionsProcess dynamics refers to changes in the process that occur due to distur-bances or changes in the set point. Process gain changes ar...

  • Page 679

    667CHAPTER14Process Responsesand Transfer FunctionsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSECTION4PLC ProcessApplicationsresponse will be at 99.33% of its final value. In Laplace form, the transferfunction of a first-order system has the form:HAss() ==+Ou...

  • Page 680

    668SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER14Process Responsesand Transfer Functionsoverdamped responseprocess controlprocess gainprocess variablesecond-order responseset pointsteady statestep responsestep testtransfer...

  • Page 681

    PROCESS CONTROLLERSAND LOOP TUNINGCHAPTERFIFTEENConfusion worse confounded.—John MiltonIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 682

    670SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningCHAPTERHIGHLIGHTSIn the previous chapter, we explained some important topics, such asprocess variable responses and transfer functions, tha...

  • Page 683

    671CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPVResponsetPVResponsetPVResponset(a)(b)(c)Figure 15-1. (a) Stable, (b) conditionally stable, and (c) unstable responses.15-2 CONTROLLER AC...

  • Page 684

    672SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningwhere Hc(s) and Hp(s) are the controller and process transfer functions inLaplace form.Figure 15-2. Open-loop system configuration.As in an...

  • Page 685

    673CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-4 illustrates another example of a direct-acting controller in whichtwo materials are mixed in an exothermic (heat-producing) bat...

  • Page 686

    674SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-6 shows the reaction of the controller to the process variable. If thecontroller senses that the temperature is too hot, it opens...

  • Page 687

    675CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-7. Reverse-acting controller controlling the temperature in a batch-heatingprocess.heating system. As the temperature becomes war...

  • Page 688

    676SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningswitch that can be used to select the desired action of the controller (direct orreverse). The control switch on a home thermostat is an ex...

  • Page 689

    677CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comsignal (see Figure 15-10b). In this section, we will discuss discrete-modecontrollers. In the next section, we will explore continuous-mode...

  • Page 690

    678SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-11. Two-position discrete controller controlling a heater.zero. However, most heating systems have an error deadband, meaning tha...

  • Page 691

    679CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comon the direction of the process variable. If the value of the process variable isdecreasing within the deadband, then the controller is OFF...

  • Page 692

    680SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningAt that time, the controller will turn OFF and remain OFF (through point 4)until the error drops to –∆E (point 5), causing the cycle to...

  • Page 693

    681CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-14. Example 15-1 (a) process variable response and (b) hysteresis curve.EXAMPLE 15-2Figure 15-15 shows a mixer tank that is heate...

  • Page 694

    682SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningsystem linearly loses (cools) 4°F per minute; when the heater isapplied, the system gains 8°F per minute. The system starting point isat ...

  • Page 695

    683CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comwhere:Tempthe value of thecurve (temperature) when the controller is OFFTempthe value of thecurve when the controller is ONTempthe value of...

  • Page 696

    684SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningtemperature to go from 210° to 190°. This value is the same as thetime calculated for the curve Temp1(t), which is 2.5 minutes. Therefore...

  • Page 697

    685CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-17. Undershoot and overshoot of the error deadband due to lag.However, once the temperature reaches 190°F and the heater turnsON...

  • Page 698

    686SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThis will make the upper temperature 214°F (210°F + 4°F). The finalperiod of oscillation, which is the last half of the curve, is the co...

  • Page 699

    687CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-18. Three-position, direct-acting controller’s output in response to error.Figure 15-19. Contact output interface implementing ...

  • Page 700

    688SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-20. (a) A discrete mode, multiposition controller and (b) its output.conjunction with multiple output contact cards to obtain mul...

  • Page 701

    689CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-21. Steam heating system controlled by a three-position controller.V2V1SteamOFFOFFONOFFONON0%50%100%PV = 210°F(E = +10)PV = SP =...

  • Page 702

    690SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-22. (a) Response plot and (b) controller output of the heating system inFigure 15-21.15-4 CONTINUOUS-MODE CONTROLLERSMost proces...

  • Page 703

    691CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-23. Block diagram of a continuous-mode controller.modes in one controller forms the industry standard known as PID control.Table ...

  • Page 704

    692SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningin applications. This is due to the derivative action’s response, whichproduces a high output but only for a short period of time. This h...

  • Page 705

    693CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comUsing this equation, a proportional controller can adjust the value of thecontrol variable according to time and error by replacing the CV(...

  • Page 706

    694SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningresponse that spans from 60°F to 180°F, equaling a range of 120°F (180°F –60°F). However, if the controller only needs to exert cont...

  • Page 707

    695CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comerror within the control band. The error percentage range is equal to theproportional band percentage, because both express how much the pr...

  • Page 708

    696SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningESPPVPVPV=−−=°−°°−°= −°−°=minmax.%120135601801512012 5FFFFFFThis error (12.5% above the set point over the PV range) in t...

  • Page 709

    697CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-29. Example controller’s transfer function.The proportional gain for a reverse-acting controller (see Figure 15-30) iscalculate...

  • Page 710

    698SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThe gain is:KPBP =−= −=−01001001001%%%%%/ %If the process variable temperature is 160°F, the percentage error over thefull variable ...

  • Page 711

    699CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCLOSED-LOOP PROPORTIONAL CONTROLFigure 15-31a illustrates a typical open-loop process control system wherethe process variable and transfer...

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    700SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThe term Hc(s) represents the controller’s transfer function, while the termHp(s) represents the process’s transfer function. The proce...

  • Page 713

    701CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.commanual reset, allowing the operator to change the bias, or operating point, ofthe controller. This changes the level of controller output a...

  • Page 714

    702SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningEXAMPLE 15-5The closed-loop system shown in Figure 15-34 has a first-orderprocess (Hp) with a gain of 5 and a time constant of τ = 30 seco...

  • Page 715

    703CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPVSPsssssssssss()()= ( )( )( )( )[]+= ( )+()= ( )()=++=+++++++++881140403014030415301530140301403014030140 301301This transfer function ind...

  • Page 716

    704SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningL−−+ =−111AssAet()secττHence, in the time domain, the process variable response will be equal t...

  • Page 717

    705CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThe closed-loop response of the controller and process, however,would have a much smaller gain (in this case, 0.976) due to thenegative fee...

  • Page 718

    706SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuning15-6 INTEGRAL CONTROLLERS (I MODE)An integral controller provides an output whose rate of change is propor-tional to the error deviation. ...

  • Page 719

    707CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comwith a proportional controller, an integral controller will bring the system’sresidual error to zero. An integral controller’s output (...

  • Page 720

    708SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-38. Integral gain.Figure 15-39. Integral controller’s response to a step change in the process variable.value, meaning that the...

  • Page 721

    709CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTo further illustrate the effect of the measured error on the control variableoutput, let’s examine Figure 15-40, which shows the graph o...

  • Page 722

    710SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThe gain of an integral controller (KI) is defined by the equation:KECVIdCVdt= ()=change in % ofper secondchange in % of errorA value of KI...

  • Page 723

    711CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-41. (a) Integral gain curves and (b) the family of curves for an integral controller.(i.e., PV = 200°F), then after one second t...

  • Page 724

    712SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-42. Integral controller output response to a change in error.If the error as shown in Figure 15-42 drops to 10%, the output will ...

  • Page 725

    713CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTKII=1The TI variable is used by some manufacturers to allow the user to indirectlyenter the integral gain into the controller. If the inte...

  • Page 726

    714SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningAs Figure 15-44 illustrates, after 2 seconds of integral action, thecontroller output will be 54%:CVKEdtCVEttIttttt()()(.)%[.][()]%%=======...

  • Page 727

    715CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-44. Controller output.Therefore, at the end of the next 3 seconds, the controller output willbe 57%:CVKEdtCVEttIttttt()()(.)%[.][...

  • Page 728

    716SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningintegral controller (see Figure 15-45) to form a proportional-integral (PI)controller. This type of controller has a fast response time (pr...

  • Page 729

    717CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-46. (a) Parallel and (b) series PI controllers.Both of these types of PI controllers eliminate error offset and have a fasterresp...

  • Page 730

    718SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningWhen t = TI, the term KPE is repeated once by the integral action, in this casein the period from t = 0 to t = 1 minute. Figure 15-47a illu...

  • Page 731

    719CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSOLUTION(a) The error created in the system over the PV range is:E (%)%=°−°°−°=1551502001005FFFFThe given values of the proportiona...

  • Page 732

    720SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuning(b) The integral gain will equal the proportional gain in 1.667 minutes:KEKK EtttPPI==()= ()=−−( %)( %)( %) . min ( %)( )..min2520 6510...

  • Page 733

    721CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThe signs of the proportional gain (KPE) and the combined proportional-integral gain ( K K EdtPI∫) terms are important when determining t...

  • Page 734

    722SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningCVK EKEdtCVPIttnew =−+()+∫=00()The negative sign in the proportional gain term ensures that the controllerwill operate as reverse-actin...

  • Page 735

    723CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTherefore, the closed-loop transfer function is:PVSPHc HpHc Hpsssssssssssssssssssssss()()()()()()......=+= ( )( )[]( )( )+[]=()()=+++++++++...

  • Page 736

    724SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThus, the error will be zero at steady state:ESPPV=−=−=110Figure 15-51. Saturation of the control variable output.A PI controller may c...

  • Page 737

    725CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com15-8 DERIVATIVE CONTROLLERS (D MODE)STANDARD DERIVATIVE CONTROLLERSThe output of a derivative controller is proportional to the rate of ch...

  • Page 738

    726SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-53 illustrates the derivative gain transfer function in a direct-acting system by indicating the corresponding controller outputs...

  • Page 739

    727CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-54. Derivative controller response for the transfer function shown inFigure 15-53a.Derivative action is not used by itself in a c...

  • Page 740

    728SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningMODIFIED DERIVATIVE CONTROLLERSDerivative action may also be expressed in terms of the change in theprocess variable rate over time:CVKdPVd...

  • Page 741

    729CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comESPPVCVKdEdtCVKdSPdtdPVdtCVKdSPdtKdPVdtCVtDtDtDDt=−=+= − += −...

  • Page 742

    730SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFor :(parallel)series)For (parallel)(series)dEdtCVK EKdEdtCVCVK EK KdEdtCVdPVdtCVK EKdPVdtCVCVK EK KdPVdtCVtPDttPPDttPDttPPDt()()()()()()()...

  • Page 743

    731CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-58. Proportional-derivative controller’s response to an error.These equations are formed by adding the equations for the propor...

  • Page 744

    732SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThe derivative action in a PD controller adds stability to a closed-loopsystem by reducing the amount of overshoot and undershoot in the sy...

  • Page 745

    733CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-60. Reaction of a closed-loop system to a unit step.thus having the opposite sign of the proportional gain. Therefore, withderiva...

  • Page 746

    734SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningthis closed-loop system for several values of derivative gain KD (or TD,derivative time). As the gain of the derivative action increases, t...

  • Page 747

    735CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comEXAMPLE 15-9The closed-loop system described in Examples 15-5 and 15-8 em-ployed proportional and proportional-integral controllers, respec...

  • Page 748

    736SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningPVSPsssssss()()=++=++4060041 63014060041 630Applying the final value theorem to this ...

  • Page 749

    737CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-64 illustrates the serial and parallel system configurations for aPID controller, along with their respective closed-loop equatio...

  • Page 750

    738SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-64. (a) Parallel and (b) serial PID controllers.(a) Parallel PID controllerStandardDerivativedEdtModifiedDerivativedPVdtHcEPVCVSP...

  • Page 751

    739CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.compurposes of obtaining an equation for the best controller to govern this system,the delay can be omitted during the initial controller calc...

  • Page 752

    740SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningSo, for a perfect system, the controller’s transfer function should be theinverse of the processor’s transfer function. Therefore, the ...

  • Page 753

    741CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comtype of control for manufacturing processes. In fact, of all the PID configu-rations shown in Figure 15-64, perhaps the most commonly used ...

  • Page 754

    742SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningThe digital PID algorithm implemented in PLC systems calculates the errorby approximating the area between the process variable and the set...

  • Page 755

    743CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comINTEGRAL (RESET) WINDUPAs discussed in Section 15-7, integral (or reset) windup is a problematiccondition that occurs in PI and PID control...

  • Page 756

    744SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningDuring a manual-to-automatic transfer in a PLC system, the PID interfaceprocessor may also set the set point equal to the process variable....

  • Page 757

    745CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-72. Temperature control systems with (a) single and (b) cascaded PID controllers.(a)(b)HcE = SP – PVCVPVSP +–ΣSteamBatchTemp...

  • Page 758

    746SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningcontrol. In the cascade configuration, the batch tank controller provides theset point for the steam jacket temperature controller, which i...

  • Page 759

    747CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-74. Cascade control directly to a PID interface.BUMPLESS CASCADE CONTROLPLC systems also provide bumpless transfer in cascade con...

  • Page 760

    748SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningFigure 15-75. Bumpless transfer in cascaded PID controllers.Hp2Hp1ESP+–ΣPV1AutoAutoManAutoManAutoHc1PIDManualHc1ESP+–ΣPV2PV2PV1AutoAu...

  • Page 761

    749CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-76. Process disturbances.the process variable. The process variable response to both system distur-bances and the controller acti...

  • Page 762

    750SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningTable 15-2 shows the characteristics of each type of process variable re-sponse. The tuning parameters of the system will have a decisive i...

  • Page 763

    751CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comZIEGLER–NICHOLS OPEN-LOOP TUNING METHODJohn Ziegler and Nathaniel Nichols developed the Ziegler-Nichols open-loop tuning method in 1942, ...

  • Page 764

    752SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuning3. Find the reaction rate. Extend the line for the process variableresponse before the step change (see point A in Figure 15-80). Drawa tan...

  • Page 765

    753CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 15-80. Process variable response to step change.process variable response line (point D). Subtract the time at whichthe step change ...

  • Page 766

    754SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningTable 15-3. Ziegler-Nichols open-loop tuning equations.There are two problems with the Ziegler-Nichols open-loop tuning method.The first pr...

  • Page 767

    755CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comEXAMPLE 15-10The Ziegler-Nichols open-loop tuning method was used to obtain theprocess response shown in Figure 15-81. Find the tuning para...

  • Page 768

    756SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningangle formed by the intersection of the tangent line with the PV lineextension:NPVt==−−==∆∆685053 15181859 730%%min.min%.min.The PI...

  • Page 769

    757CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comcannot tolerate as much oscillation as produced by the quarter-amplituderesponse. The ITAE method, which is based on the minimization of th...

  • Page 770

    758SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop Tuningwhere the actual response, not the tangent, has a value of 63.2% of the finalsteady-state value. Whereas the final value of the response at...

  • Page 771

    759CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 15-4. ITAE open-loop tuning equations.Type of ControllerLoop TuningConstantTuning EquationProportional-Integral-Derivative (PID)Propo...

  • Page 772

    760SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningHpHcEPVPVSP+–ΣPIDIncrease KP until...PVt… a constant amplitude oscillation occursFigure 15-85. Ziegler-Nichols closed-loop tuning ...

  • Page 773

    761CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com1. Implement proportional-only control. Remove all integral andderivative actions. In most controllers, the removal of integral time(TI) is...

  • Page 774

    762SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningTable 15-5. Ziegler-Nichols closed-loop tuning equations.For the example system in Figure 15-86, the tuning constants for eachcontroller mo...

  • Page 775

    763CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAnother problem with this closed-loop technique is that the majority ofprocess control loops in manufacturing operations cannot tolerate os...

  • Page 776

    764SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningPIDTuningSoftware ProcessPLCProcessorPIDInterfaceFigure 15-88. Software loop tuning.SOFTWARE TUNING METHODSAnother method for tuning PID co...

  • Page 777

    765CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comExperTune®, by ExperTune, Inc., identifies the transfer function of theprocess during the tuning test (see Figure 15-90), thus providing i...

  • Page 778

    766SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningSoftware tuning systems also allow “what if” analysis, meaning that theysuggest new controller constants given hypothetical process val...

  • Page 779

    767CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comIntegral action tends to ignore high-frequency changes, such as noise orrapid transients, in the process. Although this control mode elimin...

  • Page 780

    768SECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER15Process Controllersand Loop TuningBumpless transfer refers to a controller’s ability to switch from manual toautomatic control and vice versa without a step change in the ...

  • Page 781

    769CHAPTER15Process Controllersand Loop TuningSECTION4PLC ProcessApplicationsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comproportional controllerproportional-derivative controllerproportional-integral controllerproportional-integral-derivative controllerquarter...

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    ADVANCED PLC TOPICSAND NETWORKSSECTION FIVE•Artificial Intelligence and PLC Systems•Fuzzy Logic•Local Area Networks• I/O Bus NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

  • Page 785

    ARTIFICIAL INTELLIGENCEAND PLC SYSTEMSCHAPTERSIXTEENComputers can figure out all kinds of prob-lems, except the things in the world that justdon’t add up.—James MagaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 786

    774SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsArtificial intelligence (AI) is an area of computer science that has beenaround for some time. In fact, the conceptual design o...

  • Page 787

    775CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comEach of these types of AI systems have similar characteristics, and in fact, thesystems evolve sequentially. As the systems bec...

  • Page 788

    776SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC Systemsanalysis. The use of statistical data analysis lets the system predict outcomesbased on current process assessments. The outcom...

  • Page 789

    777CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 16-1. Artificial intelligence system architecture.GLOBAL DATABASEThe global database section of an AI system contains al...

  • Page 790

    778SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsAccordingly, the knowledge database of a diagnostic system is less complexthan that of a knowledge system; likewise, the knowle...

  • Page 791

    779CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comengineer may implement this information as the following rule: IF the volumeis less than the set point, THEN annunciate a syste...

  • Page 792

    780SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsA slightly different degree of complexity occurs in a rule-based knowledgerepresentation when the rule has several probable cau...

  • Page 793

    781CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com16-5 KNOWLEDGE INFERENCEKnowledge inference is the methodology used for gathering and analyzingdata to draw conclusions. Knowl...

  • Page 794

    782SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC Systemsdepends on the degree of inferencing that occurs on a local basis. Blackboardarchitecture is the name given to this type of lar...

  • Page 795

    783CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTwo different types of fact searching occur within the forward chainingmethod: depth first and breadth first. Both searches dea...

  • Page 796

    784SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsBACKWARD CHAINING STATISTICAL AND PROBABILITY ANALYSISEXAMPLE 16-2A control system monitors and controls a cooker in a temperat...

  • Page 797

    785CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comIf a high-limit alarm occurs (see Figure 16-7c), a normal system wouldcontrol the cooker by adjusting its temperature loop. How...

  • Page 798

    786SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsPX YPY XP XPY XP XP Y XP X(/ )[ ( / )][ ( )][ ( / )][ ( )] [ ( /)][ ( )]=+where:PY XYXPXXPY XYXPXX(/)()(/)()==== the probabilit...

  • Page 799

    787CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com•The probability that the boxes will go to the right placewhen the solenoid is faulty is 35%.•The probability that the boxe...

  • Page 800

    788SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsCONFLICT RESOLUTIONA conflict occurs when more than one rule is triggered at the same time in anAI system. Normally, a system s...

  • Page 801

    789CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 16-8. Batching system configuration.Figure 16-9. Main control program flowchart.Temp Switch TS1Temp Switch TS2Steam Val...

  • Page 802

    790SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsFigure 16-10. Temperature and steamvalve relationship.Figure 16-11. Temperature controlsubroutine.Istemp at800°C?Open valveto ...

  • Page 803

    791CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 16-12. Batching control routine.NoClose Sol A,pump A OFFGo to subroutine(check faults and print)Open Sol B,pump B ONFini...

  • Page 804

    792SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC Systems•A pump motor provides the necessary pressure to send the ingredientsthrough the line.•Before any of the ingredients are po...

  • Page 805

    793CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comRULE DEFINITIONSBased on the process control description and the possible failures, the systemhas the rules described in Table ...

  • Page 806

    794SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER16Artificial Intelligenceand PLC SystemsTable 16-2. Batching system rules.seluR1.ssecorperitnehtiwdeecorP.KOnoitarepoNEHT,tluafonsierehtFI2.erusserpkcehcNEHT,evlavehtn...

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    795CHAPTER16Artificial Intelligenceand PLC SystemsSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comKEYTERMSWe could add intelligence to the system by storing data from the process (e.g.,how many times the pump has been turned ...

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

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    FUZZY LOGICCHAPTERSEVENTEENSlumber not in the tents of your fathers. Theworld is advancing. Advance with it.—Giuseppe MazziniIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    798SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFuzzy logic provides PLCs with the ability to make “reasoned” decisionsabout a process. In this chapter, we will introduce you to the basics of fuzzylo...

  • Page 811

    799CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comIn real life, this fuzzy logic temperature algorithm can be associated withthe decision you make about the type of clothing you wear at different timesof t...

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    800SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicEXAMPLE 17-1Figure 17-4 illustrates one representation of age (i.e., young, middleage, and old) based on the number of years a person has been alive.In thi...

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    801CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comGrade10354555AgeYoungOldMiddleAgeFigure 17-5. Fuzzy logic age ranges.(b) Figure 17-6 illustrates the fuzzy logic representation for the fourage groups: you...

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    802SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicIn either case—that all Cretans lie or that all Cretans do not lie—a contradic-tion exists, because both statements are true and false. Russell found t...

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    803CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comthen go through the fuzzy logic process, where the processor would analyzea database to obtain an output. Fuzzy processing involves the execution ofIF...TH...

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    804SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicwhich opens or closes according to its grade on the output chart. Figure 17-10 illustrates a fuzzy logic cooling system chart with both input and outputgra...

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    805CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com17-4 FUZZY LOGIC CONTROL COMPONENTSFigure 17-11. Fuzzy logic controller operation.In this section, we will explain the main components of a fuzzy logiccon...

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    806SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogic•membership functions•labelsMembership Functions. During fuzzification, a fuzzy logic controllerreceives input data, also known as the fuzzy variable, ...

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    807CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-14. Asymmetrical membership functions.Grade10ZΠΛSFigure 17-15. Incorrect membership function shapes.at each end point must have a value of 0 or...

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    808SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-16 illustrates an example of an input variable with seven Λ-shapedmembership functions using all of the possible labels. A group of membershipfu...

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    809CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comRule Evaluation. Fuzzy logic is based on the concept that most complicatedproblems are formed by a collection of simple problems and can, therefore,be easi...

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    810SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicto determine the final outcome. Figure 17-20a illustrates an example of twofuzzy inputs, X1 and X2, and one fuzzy output, Y1. The rules shown in Figure17-2...

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    811CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-21. Omron’s fuzzy logic controller in a PLC system.largest grade. If rule 1 in Figure 17-20 had used an OR function instead of anAND function, ...

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    812SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicrules. An even membership function combination (e.g., a system with 6 labelsfor one input and 4 labels for another) will have a 24-rule matrix. When moreth...

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    813CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-24. Fuzzy logic process: (a) inputs, (b) rules, (c) outputs, (d) output curves,(e) combined output curve, and (f) the output signal for the field...

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    814SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogic0.4PL). Note that the 0.6 grade is applied to output ZR and the 0.4 grade isapplied to output PL because the user programmed the rules that way. Figure17-2...

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    815CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-27. Three–membership function fuzzy set and its rules.SOLUTION(a) Figure 17-28a shows the two rules triggered (rules 1 and 2) by the37.5% FI in...

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    816SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogic(b) Figure 17-29 shows the logical sum that the fuzzy controller willperform. This logical sum is the result of geometrically adding theareas of the two ou...

  • Page 829

    817CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-31. (a) Rule matrix and (b) fuzzy set.(a) Indicate the rules that are triggered for the two input conditions X1= 60% and X2 = 75%, as well as all...

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    818SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicDEFUZZIFICATION COMPONENTSFigure 17-33. (a) Triggered outputs and (b) outcome curve.grade of 0.8. Figure 17-30 presented these grade levels. Because therul...

  • Page 831

    819CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com•maximum value•center of gravityMaximum Value Method. The maximum value method bases the finaloutput value on the rule output with the highest membersh...

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    820SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicCenter of Gravity Method. The center of gravity method, also referred toas “calculating the centroid,” mathematically obtains the center of mass of the...

  • Page 833

    821CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThe center of gravity method applies to noncontinuous, or discrete, outputmembership functions, as well as continuous ones. In noncontinuous func-tions, th...

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    822SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-38. Centroid value approximation.value (i.e., counts) divided by the sum of the rule outcome grades. In this case,the fuzzy logic controller will...

  • Page 835

    823CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comof the speed and distance. Illustrate these rules in matrix form. (c)Using the center of gravity method, calculate the value of the outcomeif car 1 is trav...

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    824SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-40. The fuzzy input sets—(a) distance and (b) speed—and (c) the fuzzyoutput set, braking.Table 17-1. The fuzzy system’s rules.10ShortNLNorm...

  • Page 837

    825CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com(c) Figures 17-42a and 17-42b illustrate the graphs for the inputs d =45 ft and v = 65 mph. Each input triggers (crosses) two membershipfunctions—input d...

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    826SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-43. Output calculation.short and the 65 mph speed is 37.5% normal. The rule implies twobraking outputs (…THEN B = PL) based on these inputs, on...

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    827CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-44. (a) Outcome summary for all four rules, (b) illustration of the outputs,and (c) defuzzification of the result.10NLZPL10NLZRPL0.750.6250.750.3...

  • Page 840

    828SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-45. Two-conveyor packaging system.17-5 FUZZY LOGIC CONTROL EXAMPLEMotor 1Encoder 1PE1PE2To wrappingmachineMotor 2Encoder 2PE3PE4ConnectionConvey...

  • Page 841

    829CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.commain program must adjust the two fuzzy inputs, the part/box offset and the rateof change of the offset, so that the data is centered around a value of 2048...

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    830SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-48. Fuzzy system flowchart.the system will slow conveyor B until the part is at PE1, at which time thefuzzy controller will indicate an increase ...

  • Page 843

    831CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comMEMBERSHIP FUNCTIONS AND RULE CREATIONFigure 17-49. Three fuzzy sets used for the conveyor example: (a) deviation betweenpart and box (input), (b) rate of ...

  • Page 844

    832SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-50. Fuzzy logic rule matrix.Table 17-2. Fuzzy system rules.variable is from 0 to 4095 counts. This corresponds to a range of ±24 inchesfor the d...

  • Page 845

    833CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comOnce the fuzzy controller receives the inputs, it will determine the finaloutput value based on a logical addition of the selected outcomes. Theoutcome cal...

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    834SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-52. Part/box configuration.SOLUTION(a) Figure 17-53 shows the four rules that will be triggered by the inputreading, along with the selected outc...

  • Page 847

    835CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com(b) Figure 17-54 shows the logical sum of all the rules’ actions. Thecentroid for this output is located at approximately 2990 counts, whichincreases the...

  • Page 848

    836SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicusing standard control methods. A system designer should not use fuzzylogic control just because it is available. Rather, he or she should use itbecause it...

  • Page 849

    837CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.combefore the batch temperature, the fuzzy controller can take corrective actionby suggesting an increase in the steam volume going into the jacket. Thisopera...

  • Page 850

    838SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFuzzyControllerProcessFuzzy Logic SystemSystem Block DiagramPure Fuzzy ControlExistingConventionalControllerProcessParallel Fuzzy ControlFuzzyControllerExi...

  • Page 851

    839CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFUZZY INFERENCE ENGINEThe selection of the fuzzy inference engine encompasses the determinationof how the fuzzification process will take place (e.g., the ...

  • Page 852

    840SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogiclabels covering the same input data range as a three-label fuzzy set (refer toFigure 17-58), the one with five labels will provide more fine-tuned control,...

  • Page 853

    841CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comRule Decision Making and Outcome Determination. The easiest way toformulate the rules for a fuzzy logic controller is to first write them asIF…THEN state...

  • Page 854

    842SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicRemember that, before defuzzification occurs, the fuzzy controller adds allthe outcomes based on the appropriate logic. If the rule contains a logicalAND f...

  • Page 855

    843CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 17-63. (a) Seven outputs with the final output selected using (b) the left-most max-imum, (c) the right-most maximum, and (d) the center of gravity ...

  • Page 856

    844SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER17FuzzyLogicFigure 17-65. A gap in a fuzzy input set.Figure 17-64. Improper coverage of inputs leading to an error condition.input X2 intersects label ZR anywhere in t...

  • Page 857

    845CHAPTER17FuzzyLogicSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comKEYTERMScenter of gravity methodcentroiddefuzzificationfuzzificationfuzzy logicfuzzy processingfuzzy setgradelabelmaximum value methodmembership functionrule

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

  • Page 859

    LOCAL AREANETWORKSCHAPTEREIGHTEENSynergy means behavior of whole systemsunpredicted by the behavior of their parts.—Richard Buckminster FullerIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    848SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksCHAPTERHIGHLIGHTSAs control systems become more complex, they require more effectivecommunication schemes between the system components. Some machi...

  • Page 861

    849CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com • capable of supporting real-time control • high data integrity (error detection) • high noise immunity • high reliability in harsh enviro...

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    850SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksFigure 18-2. LANcity cable TV network.ADVANTAGES OF LANSBefore local area networks came into use, two other methods were employedto implement commu...

  • Page 863

    851CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comof usable data among PLCs and other hosts. Moreover, because each PLCin the network can communicate independently with the others (without theuse o...

  • Page 864

    852SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksFigure 18-4. Large network using many different topologies.ClosedCircuitTVVoiceCommunicationsConverterBroadbandModemHeadEndModemBroadbandModemBroad...

  • Page 865

    853CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSTARAs mentioned previously, the first PLC networks consisted of a multiporthost computer with each port connected to the programming port of a PLC...

  • Page 866

    854SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksCOMMON BUSThe common bus topology has a main trunkline to which individual PLCnodes are connected in a multidrop fashion (see Figure 18-6). A coaxi...

  • Page 867

    855CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPLCPLCPLCPLCFigure 18-8. Ring topology.Some LAN manufacturers have overcome the problem of node failure in aring topology by using a wire center. T...

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    856SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksPLCPLCPLCPLCWireCenterDATA TRANSMISSION TECHNIQUESFigure 18-9. Star-shaped ring topology with a wire center.Several transmission techniques are use...

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    857CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com18-4 NETWORK ACCESS METHODSAn access method is the manner in which a PLC accesses the network totransmit information. In other words, it defines t...

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    858SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworks•with a transmitter that can be set to a high independence state•with a passive current-loop transmitter, wired in series with the othertransmi...

  • Page 871

    859CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comtemporary, right to control the network (i.e., transmit information). Thestation with the token has the exclusive right to transmit on the network;...

  • Page 872

    860SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworks18-5 COMMUNICATION MEDIAThis section discusses the communication media (i.e., cables) used to imple-ment local area networks. If installed properl...

  • Page 873

    861CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comBASEBAND COAXIAL CABLEBaseband coaxial cable, which can send one signal at a time at its originalfrequency, can transmit data in a local area netwo...

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    862SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksbut not from use in star or ring topologies. In addition, fiber-optic cable isthree to four times more expensive than baseband coaxial cable, and o...

  • Page 875

    863CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comRESPONSE TIMEResponse time (RT), as used in this book, is the time between an inputtransition at one node and the corresponding output transition a...

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    864SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworks80% of the baud rate due to the start and stop bits that accompany each 8 databits. In these systems, the time intervals between transmitted charac...

  • Page 877

    865CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPLC on the network, along with various monitoring and control functions,if available. If a network-compatible programming device is not available,a...

  • Page 878

    866SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksis energized, the network contact, Net 200 (–| |–), in PLC #2 will close. PLC#2 can use this contact like any other contact in its ladder progr...

  • Page 879

    867CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comOSI REFERENCE MODELNetworks follow a protocol to implement the transmission and reception ofdata over the network medium (e.g., coaxial cable). In ...

  • Page 880

    868SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksTo understand this seven-layer architecture, let’s examine a familiar every-day example, an interoffice memo (see Figure 18-15). Imagine that two...

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    869CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 18-15. Seven-layer architecture.•The mail room clerk takes the memo, makes sure that it has the rightpostage and address, and puts it in t...

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    870SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksFigure 18-16. IEEE 802 standard.IEEE STANDARDSThe Institute of Electrical and Electronic Engineers (IEEE) computer societyestablished the Standards...

  • Page 883

    871CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comand Intel, the IEEE accepted it with only a few modifications to make itcomply with the 802.3 (CSMA/CD bus). The ISO has also taken Ethernet asa st...

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    872SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksTCP/IP PROTOCOLMost manufacturers who offer Ethernet compatibility to implement supervi-sory functions over equipment controlling plant floor funct...

  • Page 885

    873CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 18-18. Allen-Bradley’s PLC-5 controllers with built-in TCP/IP-over-Ethernet protocol.Figure 18-19. PLC connected directly to an Ethernet n...

  • Page 886

    874SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworks18-8 NETWORK TESTING AND TROUBLESHOOTINGBefore a local area network is installed, the designer should test it to ensurethat it not only performs t...

  • Page 887

    875CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com18-9 NETWORK COMPARISON AND SELECTION CRITERIANETWORK COMPARISONThe most distinctive differences among local area networks are the transmis-sion o...

  • Page 888

    876SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER18Local AreaNetworksby too many nodes trying to communicate at the same time. This short delaymay be acceptable in an office environment using Ethernet (IEEE 802.3),wh...

  • Page 889

    877CHAPTER18Local AreaNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.coma gateway or directly through the PLC using the local area network. Incontrast, PLC manufacturers’ proprietary networks may not have as manycompa...

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

  • Page 891

    I/O BUSNETWORKSCHAPTERNINETEENNecessity is the mother of invention.—Latin ProverbIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 892

    880SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksAdvances in large-scale electronic integration and surface-mount technology,coupled with trends towards decentralized control and distributed intelli-...

  • Page 893

    881CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 19-1. I/O bus network block diagram.Information NetworkPlant ComputingSystemLocal Area NetworkWindowsComputerSupervisoryPLCsPLCPLCPLCI/O Device...

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    882SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksFigure 19-3. Connections for an I/O bus network.Figure 19-4. Intelligent field device.Figure 19-2. Connection between a PLC, a local area network, and...

  • Page 895

    883CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comdecrease because of a dirty lens, or a limit switch can report the number ofmotions it has performed. This type of information can prevent I/O devicem...

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    884SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksbus networks that include discrete devices, as well as small analog devices,are called byte-wide bus networks. These networks can transfer between 1an...

  • Page 897

    885CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAlthough no proclaimed standards exist for device bus network applications,several de facto standards are emerging due to the availability of company-...

  • Page 898

    886SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksdigital communication was one of the major reasons for the establishmentof I/O bus networks. Digital communication allows more than one fielddevice to...

  • Page 899

    887CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 19-7. InterBus-S I/O block interfaces.A PLC or computer in an InterBus-S network communicates with the bus ina master/slave method via a host c...

  • Page 900

    888SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksFigure 19-9. An InterBus-S network with a host controller interface to a PLC.I/O device addresses in an InterBus-S network are automatically determine...

  • Page 901

    889CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 19-1. Features and benefits of the InterBus-S network.scitsiretcarahCkrowteNserutaeFS-suBretnIstifeneBresU:)1reyaL(reyaLlacisyhPerutcurtslocotor...

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    890SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksTable 19-2. Speed-versus-length tables for (a) DeviceNet and (b) SDS CANbus networks.Figure 19-10. (a) A CANbus communication link and (b) a CANbus fo...

  • Page 903

    891CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThe DeviceNet byte-wide network can support 64 nodes and a maximum of2048 field I/O devices. The SDS network can also support 64 nodes; however,this n...

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    892SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksBecause an SDS network can transmit many bytes of information in the formof variable length messages, it can also support many intelligent devices tha...

  • Page 905

    893CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 19-13. (a) Information transfer through a CANbus network and (b) Allen-Bradley’sCANbus DeviceNet scanner.(a)(b)Courtesy of Allen-Bradley, Hig...

  • Page 906

    894SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksAs mentioned earlier, the SDS CANbus network can handle 126 addressableI/O devices per network per channel. To increase the number of connectabledevic...

  • Page 907

    895CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comactuators require only one bit of data to operate. By minimizing their datatransmission capabilities, bit-wide device bus networks provide optimumperf...

  • Page 908

    896SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksASI networks require a 24-VDC power supply connected through a two-wire,unshielded, untwisted cable. Both data and power flow through the same twowire...

  • Page 909

    897CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSeriplex Bit-Wide Device Bus Network. The Seriplex device bus networkcan connect up to 510 field devices to a PLC in either a master/slave or peer-to-...

  • Page 910

    898SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksnetwork can interface with analog I/O devices; however, the digitized analogsignal is read or written one bit at a time in each scan cycle. Figure 19-...

  • Page 911

    899CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com19-5 PROCESS BUS NETWORKSA process bus network is a high-level, open, digital communication networkused to connect analog field devices to a control ...

  • Page 912

    900SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksProcess bus networks will eventually replace the commonly used analognetworks, which are based on the 4–20 mA standard for analog devices. Thiswill ...

  • Page 913

    901CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFIELDBUS PROCESS BUS NETWORKThe Fieldbus process bus network from the Fieldbus Foundation (FF) is adigital, serial, multiport, two-way communication s...

  • Page 914

    902SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworkslayer on top of the application layer called the user layer. This user layerprovides several key functions, which are function blocks, device descript...

  • Page 915

    903CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 19-3. Fieldbus physical layer specifications.eriWfoepyTepyTsuBdeepS/seciveDforebmuNtnemgeSsubdleiFtnemgeSsuBweN)riaP-detsiwT/dedleihS(tnemgeSsuB...

  • Page 916

    904SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksAt a speed of 31.25 kbaud, the physical layer of the Fieldbus process networkcan support existing 4–20 mA wiring. This increases cost-effectiveness ...

  • Page 917

    905CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comtheir connection to the bus. The process information gathered through thesefunction block programs can then be passed to the host through the network,...

  • Page 918

    906SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksPROFIBUS PROCESS BUS NETWORKProfibus is a digital process bus network capable of communicating in-formation between a master controller (or host) and ...

  • Page 919

    907CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com(or cell) areas, which exercise the actual control during production. Thecontrollers at the cell level must communicate with other supervisory sys-tem...

  • Page 920

    908SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksThe Profibus-DP network, on the other hand, does not define layers 3 through7 (see Figure 19-29). It omits layer 7 primarily to achieve the high opera...

  • Page 921

    909CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThrough this hybrid medium access protocol, a Profibus network can functionas a master-slave system, a master-master system (token passing), or acombi...

  • Page 922

    910SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksAs mentioned earlier, layer 2 of the Profibus network is responsible for dataintegrity, which is ensured through the Hamming Distance HD = 4 errordete...

  • Page 923

    911CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comtype of communication standard (i.e., RS-485, RS-422, etc.) varies depend-ing on the specific network (e.g., DeviceNet, Seriplex, ASI, Profibus,Fieldb...

  • Page 924

    912SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksDEVICE BUS NETWORK WIRING GUIDELINESFigure 19-35. CANbus DeviceNet wiring diagram for the multiport tap in Figure 19-34.Figure 19-36. (a) Plug-and-pla...

  • Page 925

    913CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThe majority of device bus networks require that a terminator resistor bepresent at the end of the main trunk line for proper operation and transmissi...

  • Page 926

    914SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksand 500 kbits/sec. Process bus wiring installations may also require atermination block at the end of the wiring. T-junction connectors provide thecon...

  • Page 927

    915CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comI/O BUS NETWORK ADDRESSINGAddressing of the I/O devices in an I/O bus network occurs during theconfiguration, or programming, of the devices in the sy...

  • Page 928

    916SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworks19-7 SUMMARY OF I/O BUS NETWORKSThe device and process types of I/O bus networks provide incredible potentialsystem cost savings, which are realized ...

  • Page 929

    917CHAPTER19I/O BusNetworksSECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 19-41. Large plantwide network.Information Network (TCP/IP)Plant ComputerSystemLocal Area NetworkWindowsComputerSupervisoryPLCsPLCPLCPLCI/O Dev...

  • Page 930

    918SECTION5Advanced PLCTopics and NetworksIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER19I/O BusNetworksFigure 19-42. Network data transmission comparison.can be purchased at a relatively low cost. Process bus networks, on the otherhand, require devices ...

  • Page 931

    INSTALLATION ANDSTART-UPSECTION SIX•PLC Start-Up and Maintenance•System Selection GuidelinesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

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    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

  • Page 933

    PLC START-UPAND MAINTENANCECHAPTERTWENTYIf I had been present at the Creation, I wouldhave given some useful hints for the betterarrangement of the Universe.—Alfonso the Wise, King of CastilleIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 934

    922SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceThe design of programmable controllers includes a number of ruggedfeatures that allow PLCs to be installed in almost any industrial environ-ment....

  • Page 935

    923CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 20-1. Installation of a PLC-based system using modular I/O terminal blocks.an enclosure is not always required, but it is recommended for ...

  • Page 936

    924SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceTable 20-1. NEMA panel enclosure descriptions.serusolcnElenaPAMEN)tnuomecafruS(1epyTnitnempiuqedesolcneehthtiwtcatnoctsniagatcetorpotesuroodniroF...

  • Page 937

    925CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 20-2. Enclosure layout.Input Signal WirewayTerminal Block (AC Inputs)Terminal Block (DC I/O)System Signal Wireway (Inputs)System/Output Wi...

  • Page 938

    926SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceGeneral. The following recommendations address preliminary consider-ations for the location and physical aspects of a PLC enclosure:•The enclos...

  • Page 939

    927CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 20-3. Placement of PLC components.Although different controllers have different mounting and spacing require-ments, the following consider...

  • Page 940

    928SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenance•Remote I/O racks and their auxiliary power supplies are generallyplaced inside an enclosure at the remote location, following the sameplacemen...

  • Page 941

    929CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comseparated as much as possible within the rack. A suitable partitioningwould involve placing all AC modules or all DC modules togetherand, if spac...

  • Page 942

    930SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceFigure 20-5. I/O wiring from a conduit.•When designing the duct layout, the separation between the I/Omodules and any wire duct should be at le...

  • Page 943

    931CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com•The enclosure should be properly grounded to the ground bus, whichshould have a good electrical connection at the point of contact withthe enc...

  • Page 944

    932SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceIf line conditions fall below the minimum operating level, the power supplywill detect the abnormal condition and signal the processor, which wil...

  • Page 945

    933CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comEmergency Stops. The system should have emergency stop circuits forevery machine directly controlled by the PLC. To provide maximum safety,these ...

  • Page 946

    934SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenanceswitch connected to the circuit. De-energizing the control relay coil re-moves power to the input and output devices. The CPU, however, continues...

  • Page 947

    935CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com0.22 µF for 220 VAC) is placed across the disconnect to protect against anoutrush condition. Outrush occurs when the power disconnect turns off ...

  • Page 948

    936SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceFigure 20-10. Suppression of a three-phase motor lead.Figure 20-11. Power noise reduction using one of three line-filtering configurations.L1L2L3...

  • Page 949

    937CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comExcessive Heat. Programmable controllers can withstand temperaturesranging from 0 to 60°C. They are normally cooled by convection, meaningthat a...

  • Page 950

    938SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceEXAMPLE 20-1The NEMA 12 enclosure shown in Figure 20-15 contains a program-mable controller with a power supply transformer, power supplies foran...

  • Page 951

    939CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 20-14. Temperature rise graph for a NEMA 12 enclosure.Figure 20-15. NEMA 12 enclosure.Courtesy of Hoffman Engineering Co., Anoka, MNHeigh...

  • Page 952

    940SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceSOLUTION(a) To calculate the temperature rise, first calculate the total area(square feet) of the exposed sides of the enclosure. Assuming that t...

  • Page 953

    941CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAssuming that all inside components can withstand up to 60°C(140°F), the permissible temperature rise (∆T) in °F of the cooling airis:∆T =...

  • Page 954

    942SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenancenot providing power to the outputs. This arrangement will lessen the loadsupported by the transformer, allowing a smaller transformer to be used....

  • Page 955

    943CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comI/O MODULE INSTALLATIONPlacement and installation of the I/O modules is simply a matter of insertingthe correct modules in their proper locations...

  • Page 956

    944SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenance•Remove and lock out input power from the controller and I/O beforeany installation and wiring begins.•Verify that all modules are in the cor...

  • Page 957

    945CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comConnecting Leaky Inputs. Some field devices have a small leakage currenteven when they are in the OFF state. Both triac and transistor outputs ex...

  • Page 958

    946SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenanceand the input circuit. This causes a shunt on the input’s terminals. Conse-quently, the leakage current is routed through the bleeding resistor...

  • Page 959

    947CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comMost output modules are designed to drive inductive loads, so they typicallyinclude suppression networks. Nevertheless, under certain loading con...

  • Page 960

    948SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceFusing Outputs. Solid-state outputs normally have fusing on the module, toprotect the triac or transistor from moderate overloads. If the output ...

  • Page 961

    949CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com•Inspect all CPU components and I/O modules to ensure that they areinstalled in the correct slot locations and placed securely in position.•C...

  • Page 962

    950SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenancethe wrong input terminal. If no indicator turns ON, then a fault mayexist in either the input device, field wiring, or input module (seeSection 2...

  • Page 963

    951CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comin the RUN mode, depress the push button to perform the test.With the controller in single-scan mode, depress and maintain thepush button while t...

  • Page 964

    952SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand Maintenance•Load the control program into the PLC memory.•Test the control logic using one of the following methods:•Switch the controller to the TEST...

  • Page 965

    953CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPREVENTIVE MAINTENANCEPreventive maintenance of programmable controller systems includes onlya few basic procedures, which will greatly reduce th...

  • Page 966

    954SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceSPARE PARTSREPLACEMENT OF I/O MODULES20-7 TROUBLESHOOTING THE PLC SYSTEMTROUBLESHOOTING GROUND LOOPSIt is a good idea to keep a stock of replace...

  • Page 967

    955CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comconnected to ground on only one side of the chassis, preferably the PLC side.In the example shown in Figure 20-21, the shield should only be conn...

  • Page 968

    956SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceDIAGNOSTIC INDICATORSLED status indicators can provide much information about field devices,wiring, and I/O modules. Most input/output modules ha...

  • Page 969

    957CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comThe next step is to evaluate the PLC’s reading of the input module. This canbe accomplished using the PLC’s test mode, which reads the inputs...

  • Page 970

    958SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER20PLC Start-Upand MaintenanceTROUBLESHOOTING PLC OUTPUTSPLC output interfaces also contain status indicators that provide usefultroubleshooting information. Like the troubles...

  • Page 971

    959CHAPTER20PLC Start-Upand MaintenanceSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comSUMMARY OF TROUBLESHOOTING METHODSIn conclusion, the best method for diagnosing input/output malfunctions is toisolate the problem to the module,...

  • Page 972

    Industrial Text & Video Company 1-800-752-8398www.industrialtext.comThis page intentionally left blank.

  • Page 973

    SYSTEM SELECTIONGUIDELINESCHAPTERTWENTY-ONEThis is not the end. It is not even the beginningof the end. But it is, perhaps, the end of thebeginning,—Winston ChurchillIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com

  • Page 974

    962SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesIn this chapter, we will explain the procedures for selecting the properprogrammable controller for an application. We will explain how to deter-m...

  • Page 975

    963CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comComplexity and CostI/O Count3264128 512 1024 2048 4096819212345CBAFigure 21-1. PLC product ranges.also increase. Similarly, as the system complexi...

  • Page 976

    964SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesFigure 21-2. PLC Direct’s micro PLC DL105.Table 21-1. Standard features of micro PLCs.SEGMENT 2: SMALL PLCSSmall controllers are mostly used in ...

  • Page 977

    965CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 21-2. Standard features of small PLCs.Figure 21-3. Area A (SLC500) controller capable of handling up to 72 discrete and 4analog I/O.SEGMENT ...

  • Page 978

    966SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesFigure 21-4. Medium-sized PLC 5/11(left) and PLC 5/20 (right) processorswith up to 512 I/O capacity.Figure 21-5. Omron’s area B CV500 PLCwith a ...

  • Page 979

    967CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFigure 21-6. Large Mitsubishi A3NCPU controller with 2048 I/O capacity.Table 21-4. Standard features of large PLCs.Area C. Area C includes the seg...

  • Page 980

    968SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesFigure 21-7. Giddings & Lewis’s area C PIC900 with up to 3168 I/O and motion I/O, IECprogramming, and floating-point math capabilities.SEGME...

  • Page 981

    969CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 21-5. Standard features of very large PLCs.21-3 PROCESS CONTROL SYSTEM DEFINITIONsCLPegraLyreVO/I2918otpU•seitilibapachtaM•srossecorpit...

  • Page 982

    970SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelines•input/output•type of control•memory•software•peripherals•physical and environmentalINPUT/OUTPUT CONSIDERATIONSDetermining the amount ...

  • Page 983

    971CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comtemperature, and pressure, and are used to control voltage or current outputdevices. Typical interface ratings include –10 to +10 V, 0 to +10 V,...

  • Page 984

    972SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesoften when automating a process. Knowing process application and futureautomation requirements will help the user to decide what type of control,a...

  • Page 985

    973CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCentralized Control. Centralized control is used when a central PLCcontrols several machines or processes. This type of control can havemany subsy...

  • Page 986

    974SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesmemory expands incrementally in units of 1K, 2K, 4K, etc. Although thereare no fixed rules for determining the amount of memory required, certaing...

  • Page 987

    975CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comPersonal computers provide a better way to program a system if the controlprogram is large. Many PLC manufacturers provide software that allowsthe...

  • Page 988

    976SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesTable 21-6. PLC requirement checklist.tsilkcehCmetsySO/IsnoitacificepSlacipyTtnuoCO/ItnuoclatigiD)elbaxim(O/I821fomumixaMtnuocgolanA)elbaxim(O/I61...

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    977CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 21-6 continued.tsilkcehCmetsySO/IsnoitacificepSlacipyTO/IlaicepSretnuoceslupdeeps-hgiHzHk05,etomerdnalacoLtupnicinortceletsaFmuminimhtdiwesl...

  • Page 990

    978SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesTable 21-6 continued.tsilkcehCUPCsnoitacificepSlacipyTylppuSrewoPnoitairavegatloV%01–,%51+noitcetorpegatlovrevOseYgnitimiltnerruCseYylppustnerru...

  • Page 991

    979CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comTable 21-6 continued.tsilkcehCerawtfoSsnoitacificepSlacipyTgnildnaHataDsretsigerforebmuNhcaestib61,821sretsigerniezisataDDCB9999dna,76723–,76723...

  • Page 992

    980SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesTable 21-6 continued.egarotSdnagnimmargorPtsilkcehCeciveDsnoitacificepSlacipyTremmargorPlaunaMlacisyhPnoitacinummoCC232-SRrewopgnimocnItinumorFeru...

  • Page 993

    981CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.com21-4 OTHER CONSIDERATIONSAn evaluation of the previously discussed hardware and software require-ments will narrow the selection of the PLC down ...

  • Page 994

    982SECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCHAPTER21System SelectionGuidelinesstructure, programming device, and elementary instruction set. They alsohave similar memory organization and structure. Because of their similari-...

  • Page 995

    983CHAPTER21System SelectionGuidelinesSECTION6Installationand Start-UpIndustrial Text & Video Company 1-800-752-8398www.industrialtext.competSnoitcA1.dellortnocebotssecorpehtwonK2.lortnocfoepytehtenimreteDlortnocdetubirtsiD•lortnocdezilartneC•lortnoclaudividnI•3.stnemeriuqereca...

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  • Page 997

    •Logic Symbols, Truth Tables, andEquivalent Ladder/Logic Diagrams•ASCII Reference•Electrical Relay Diagram Symbols•P&ID Symbols•Equation of a Line and NumberTables•Abbreviations and Acronyms•Voltage-Current Laplace TransferFunction Relationships APPENDICESIndustrial Text & V...

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    987APPENDIXALogic Symbols, Truth Tables,and Equivalent Ladder/Logic DiagramsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAPPENDIX A: LOGIC SYMBOLS, TRUTH TABLES, ANDEQUIVALENT LADDER/LOGIC DIAGRAMSLOGIC SYMBOLS AND TRUTH TABLESANDORABY11110001000011010001100011...

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    988APPENDIXALogic Symbols, Truth Tables,and Equivalent Ladder/Logic DiagramsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comEQUIVALENT LADDER/LOGIC DIAGRAMSLogic DiagramLadder DiagramABC000011101110ABC001011101110ABC001010100110Truth TableABC000011101111ABC0000101...

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    989APPENDIXBASCIIReferenceIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCTRLASCIIKEYBDOCTDECPARITYHEXCHAREQUIVALTERNATE CODE NAMES0001EVEN00NUL@NULL, CTRL SHIFT P, TAPE LEADER0012ODD01SOHASTART OF HEADER, SOM0023ODD02STXBSTART OF TEXT, EOA0034EVEN03ETXCEND OF TE...

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    990APPENDIXBASCIIReferenceIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comCTRLASCIIKEYBDOCTDECPARITYHEXCHAREQUIVALTERNATE CODE NAMES07461EVEN3C<LESS THAN07562ODD3D=07663ODD3E>GREATER THAN07764EVEN3F?10065ODD40@SHIFT P10166EVEN41A10267EVEN42B10368ODD43C10469E...

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    991APPENDIXCElectrical RelayDiagram SymbolsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAPPENDIX C: ELECTRICAL RELAY DIAGRAM SYMBOLSSWITCHESDisconnectCircuitInterrupterLimitNeutral PositionCircuitBreakerNormallyOpenNormallyClosedHeldClosedHeldOpenActuatedMainta...

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    992APPENDIXCElectrical RelayDiagram SymbolsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comConnections, Etc. (cont.)GroundChassisOr FrameNot NecessarilyGroundedPlugandRecp.ContactsTime Delay After CoilNormallyOpenNormallyClosedNormallyOpenNormallyClosedRelay, Etc....

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    993APPENDIXDP&IDSymbolsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAPPENDIX D: P&ID SYMBOLSINSTRUMENT LINE SYMBOLSSYMBOLS FOR TRANSDUCERS AND ELEMENTSOrifice plateControl valveRotameterMagneticVenturi or nozzleFE10FE104EE4FI5Capillary tubeElectric sign...

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    994APPENDIXDP&IDSymbolsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comINSTRUMENT IDENTIFICATION LETTERINGFirst LetterSecond LetterAAnalysisAlarmBBurner, combustionUser’s choice*CUser’s choiceControlDUser’s choiceEVoltageSensory (primary element)FFlow ra...

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    995APPENDIXEEquation of a Lineand Number TablesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAPPENDIX E: EQUATION OF A LINE AND NUMBERTABLESEQUATION OF A LINEThe value of m can be calculated as: m=Y0X0=Y2 − Y1X2 − X1If the value of b is not given but the ...

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    996APPENDIXEEquation of a Lineand Number TablesIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNUMBER TABLESPowers of Two2nn102142831643256461287256851291,024102,048114,096128,1921316,3841432,76815Powers of Eight8nn108164251234,096432,7685262,14462,097,152716,777,...

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    997APPENDIXFAbbreviationsand AcronymsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAPPENDIX F: ABBREVIATIONS AND ACRONYMSAampereACalternating currentA/Danalog-to-digital converterAIartificial intelligenceANSIAmerican National Standards InstituteASCIIAmerican Sta...

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    998APPENDIXFAbbreviationsand AcronymsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comLCDliquid crystal displayLEDlight-emitting diodeLIFOlast-in first-outLRClongitudinal redundancy checkLSBleast significant bit/byteLVDTlinear variable differential transformermAmil...

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    999APPENDIXGVoltage-Current LaplaceTransfer Function RelationshipsIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comAPPENDIX G: VOLTAGE-CURRENT LAPLACE TRANSFERFUNCTION RELATIONSHIPSTable G-1 presents resistor, inductor, and capacitor voltage-current relationshipsan...

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    1001GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comGLOSSARYAC/DC I/O interface. A discrete interface that converts alternating current (AC)voltages from field devices into direct current (DC) signals that the processor canuse. It can also convert DC signa...

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    1002GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comapplication. (1) A machine or process monitored and controlled by a PLC. (2) Theuse of computer or processor-based routines for specific purposes.application memory. The part of the total system memory de...

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    1003GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comBCD. See binary coded decimal.binary coded decimal (BCD). A binary number system in which each decimal digitfrom 0 to 9 is represented by four binary digits (bits). The four positions have aweighted value...

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    1004GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.combus. (1) A group of lines used for data transmission or control. (2) Power distributionconductors.bus topology. A network configuration in which all stations are connected in parallelwith the communicatio...

  • Page 1017

    1005GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comcode. (1) A binary representation of numbers, letters, or symbols that have somemeaning. (2) A set of programmed instructions.coil. A ladder diagram symbol that represents an output instruction.cold junct...

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    1006GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comconvergence. A point in a sequential function chart where many elements flow intoone element.counter. An electromechanical device that counts the number of times an eventoccurs.counter instructions. Compu...

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    1007GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comdefuzzification. The process of converting a fuzzy logic controller’s output conclu-sions into real output data and sending the data to the field device.depth-first search. A rule evaluation method that...

  • Page 1020

    1008GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comdynamic system checkout. The process of verifying the correct operation of acontrol program by actually implementing it.EAROM. See electrically alterable read-only memory.EEPROM. See electrically erasable...

  • Page 1021

    1009GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comFALSE. As related to PLC instructions, a reset logic state associated with a binary0.fast-input interface. An intelligent I/O module that functions as a pulse stretcher,detecting very fast input pulses th...

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    1010GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comgate. A circuit having two or more input terminals and one output terminal, wherean output is present only when the prescribed inputs are present.gateway. A device or pair of devices that connects two or ...

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    1011GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.cominference engine. The section of an AI system where all decisions are made usingthe knowledge stored in the knowledge database.input. Information sent to the processor from connected devices.input device....

  • Page 1024

    1012GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comI/O bus network scanner. A device connected to a PLC that reads and writes to fielddevices connected to an I/O bus network, as well as decodes the data in the networkinformation packet.I/O module. A plug-...

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    1013GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comLaplace transform. A mathematical function used to convert differential equationsfrom the time domain into the frequency domain so that they become easy-to-manage algebraic equations.LCD. See liquid cryst...

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    1014GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.commask. A logical function used to set certain bits in a word to an established state.master. A device used to control other devices.master control relay (MCR). A hardwired or softwired relay instruction th...

  • Page 1027

    1015GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comNAND. A logical operator that yields a logic 1 output if any input is logic 0 and a logic0 output if all inputs are logic 1. This operator is a negated AND function, the resultof negating the output of an...

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    1016GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comone shot. A programming technique that sets a storage bit or output to a certain statefor only one scan.on-line. The state of being in continuous communication with the processor.open loop. A control sys...

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    1017GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.compotentiometer. A simple transducer that measures displacement based on resistancechanges due to the movement of a wiper arm.power supply. The unit that supplies the necessary voltage and current to a syst...

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    1018GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comproportional-integral-derivative controller. A continuous-mode controller thatuses proportional, integral, and derivative actions to determine the control variableoutput based on the amount of error, its ...

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    1019GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comdelay, between the transmission of the last character of a network node’s messageand its receipt of the first character of the reply.reverse-acting controller. A closed-loop controller whose control var...

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    1020GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comsingle-ended input/output. An analog I/O connection in which the commons areelectrically tied together resulting in only one return line.single-precision arithmetic. Arithmetic instructions that use one r...

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    1021GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comstorage register assignment document. A document that lists the storage registersused in a control program, including their contents and a description of theirfunction.strain gauge. A mechanical transduce...

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    1022GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comthermistor. A temperature transducer made of semiconductor material, such asoxides of cobalt, nickel, manganese, iron, and titanium, that exhibits changes ininternal resistance proportional to changes in ...

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    1023GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comtriac. A semiconductor device that functions as an electrically controlled switch forAC loads.TRUE. As related to PLC instructions, a set logic state associated with a binary 1.truth table. A table that s...

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    1024GlossaryIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comwire input module. A special input interface designed to detect short-circuit oropen-circuit connections between a module and its input devices.word. The number of bits that the central processing unit op...

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    1025IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comabsolute instruction 342AC/DC input interfaces 151–153AC output interfaces 165–167action (SFC) 387, 419–429Boolean 419–423normal 424–426pulse 423–424SFC 426–429stand-alone 422–423A/D. See ana...

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    1026IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comblock transfer instruction 354–355Boolean action 419–423Boolean algebra 64–67Boolean language 280, 369Boolean variables 378Bourdon tubes 589–590bridge circuits 566–569current-sensitive 568–569vol...

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    1027IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comcomplement 342invert 343data manipulation instructions 334–347absolute 342BCD-to-binary 340–341binary-to-BCD 340–341complement 342data comparison 334–337data conversion 340–343examine bit 346–347...

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    1028IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comdocumentation (continued)control program storage 547documentation systems 547–549internal storage address assignment document 450–451, 542I/O address assignment document 542, 450–451I/O wiring connecti...

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    1029IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comhexadecimal number system 40–41IEC 1131 standard 374–375IEC 1131-3 programming standarddata functions 375data variable types 375–376, 378function blocks 376IEC 1131-3–like languages 432–438instruct...

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    1030IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comisolation transformer 101, 932ITAE controller tuning method 756–760jump to instruction 319knowledge AI systems 775knowledge database 777–778knowledge inference 781–788knowledge representation 778–780...

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    1031IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comMAC. See medium access controlmacrostep 391manual programmer. See miniprogrammermaster control relay instruction 318–319, 458–462master rack 140master/slave bus topology 854maximum value defuzzification ...

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    1032IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comone’s complement 44ON/OFF controller. See two-position discrete controllersOR convergence 411OR divergence 410–411OR function 59–60orifice plate 593–597OSI reference model 867–869output coil instru...

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    1033IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comlag 630–631, 645–653process gain 627–628transfer functions 624–627, 633transient responses 625–627stability responses 670–671system parameters 614–623control variable 618–621error 611–612, ...

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    1034IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comscan 11, 86–91, 132I/O update scan 87program scan 87, 298–299reading fast inputs 89–91scan time 87–88scan time 87–88scratch pad area 120second-order system response 631, 651–653, 653–665critica...

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    1035IndexIndustrial Text & Video Company 1-800-752-8398www.industrialtext.comsubsystemsarchitecture 92, 146–147remote 30, 146–147subtraction instruction 327–329sum-of-the-weights method 35system abstract 537–538system configuration diagram 538–539system documentation. See d...

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