1、Fundamentals ofIndustrial Control2nd EditionD.A. Coggan, EditorFundamentals ofIndustrial Control2nd EditionD. A. Coggan, EditorPractical Guidesfor Measurement and ControlNoticeThe information presented in this publication is for the general education of the reader. Because neither the author nor the
2、 publisher have any control over the use of the information by the reader, both the author and the publisher disclaim any and all liability of any kind arising out of such use. The reader is expected to exercise sound professional judgment in using any of the information presented in a particular ap
3、plication.Additionally, neither the author nor the publisher have investigated or considered the affect of any patents on the ability of the reader to use any of the information in a particular application. The reader is responsible for reviewing any possible patents that may affect any particular u
4、se of the information presented.Any references to commercial products in the work are cited as examples only. Neither the author nor the publisher endorse any referenced commercial product. Any trademarks or tradenames referenced belong to the respective owner of the mark or name. Neither the author
5、 nor the publisher make any representation regarding the availability of any referenced commercial product at any time. The manufacturers instructions on use of any commercial product must be followed at all times, even if in conflict with the information in this publication.Copyright 2004 ISA - The
6、 Instrumentation, Systems, and Automation SocietyAll rights reserved. Printed in the United States of America. 10 9 8 7 6 5 4 3ISBN 1-55617-863-8No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechani-cal, photocopying, re
7、cording or otherwise, without the prior written permission of the publisher.ISA67 Alexander DriveP.O. Box 12277Research Triangle Park, NC 27709Library of Congress Cataloging-in-Publication Data in progressvTable of ContentsPreface ixContributors xiChapter 1 Sensors 1Applications of Instrumentation 1
8、Introduction to Sensor Fundamentals 2Standards of Measurement 10Level Measurement 11Pressure Measurement 31Flow Measurement 63Thermometers 96Weight Measurement 141Bibliography 150About the Authors 152Chapter 2 Analytical Instrumentation 153General Measurement Principals For Analyzers 154Analyzers Ta
9、rgeting Specific Stream Elements 160Analyzers for Measuring Bulk Properties 188References 199About the Authors 200Chapter 3 Chemical Process Control 201Introduction 201Responsibilities of a Process Control Engineer 202Types of Process and Control Diagrams 203Operator Acceptance 205Control Loop Hardw
10、are 206Characterizing Dynamic Behavior 214PID Control: Fundamental Characteristics of Proportional, Integral, and Derivative Action 219PID Tuning 223Advanced PID Control 233Control of MIMO Processes 243Model Predictive Control 245Case Studies 249References 265About the Author 265Table of ContentsviC
11、hapter 4 Final Control Elements 267Control Valves and ActuatorsAn Introduction 267Pressure Differential 278Control Valve Sizing 280Trim Design 296Actuators 296Valve Positioners and Accessories 300Reversible Electric Motor Drives 307Solenoid Valves 307Electric Motor Drive Control 309Regulators, Relie
12、f Valves, and Other Control Elements 312Summary 320Bibliography 321About the Author 322Chapter 5 Computer Technology 323The Digital Computer 323The Central Processing Unit (CPU) 326Computer Architecture: Components and Structure 329Computer Operating Environment 344Operating Systems 347Industrial Ap
13、plications Software 358Artificial Intelligence 378Neural Networks 382Fuzzy Logic 389Case-Based Reasoning (CBR) 393Genetic Algorithms 395Combined Approaches 398Plant Floor Applications 398Communications 401Networks 411Enterprise Computing 440Internet 444References and Bibliography 454About the Author
14、s 460Chapter 6 Control System Theory 461The Transfer Function 461Open and Closed Loops 462Block Diagrams 464Modeling 466Block Diagram Reduction Techniques 470Signal Flow Graphs 472Differential Equations 476Transform Calculus Using the Laplace Transform 477System Response and Bode Diagrams 479Stabili
15、ty 494Performance Indices 500Compensation 500The Z-Transform 501Table of ContentsviiState-Space Approach to Digital Control Systems 504Predictive Control 507Adaptive Control 508Statistical Process Control 512Expert Systems 513Conclusion 514References 515About the Author 516Chapter 7 Analog and Digit
16、al Control Devices 517Automatic Controllers 517Analog Controllers and Auxiliary Devices 519Pneumatic Auxiliary Devices 525Electric and Electronic Controllers 529Electronic Auxiliary Devices 534Digital Controllers and Auxiliary Devices 540References 550About the Authors 550Chapter 8 Distributed Contr
17、ol Systems / Digital Automation Systems 551Introduction 551DCS Architecture 557DAS Defined 564System Architecture, Functionality, and Standards 565User Interfaces 575Basic DCS/DAS Software Modules and Functionality 581Installation 584Maintenance 594Purchasing Strategies 598Migration Solutions 600Con
18、clusion 603References 603About the Authors 604Chapter 9 Programmable Logic Controllers 605Introduction 606Principles of Operation 607PLCs versus Other Types of Controllers 608Ladder Logic Concepts 611Processors 618The Memory System 626The Analog I/O System 652Special Function Interfacing 659Programm
19、ing Languages 664PLC System Documentation 668Implementing and Programming the PLC 676Guidelines for Installation, Startup, and Maintenance 685References 700About the Author 702Table of ContentsviiiChapter 10 Ergonomics and Occupational Safety 703Ergonomics As a Science 703Information Ergonomics in I
20、ndustrial Control 706Planning Control Centers 715Technical Personnel Training 727Occupational Safety 730Bibliography 736About the Author 736Chapter 11 Project Management Strategies 737Standards 737Documentation 739Instrumentation Projects 753Engineering Phases 758Site Work 779Conclusion 781Bibliogra
21、phy 781About the Author 781Appendix 1 Laboratory Standards 783Introduction to Laboratory Standards 783Pressure 789Temperature 807Liquid Level 827Miscellaneous 831About the Author 838Appendix 2 Basics of Electricity and Electronics 839Electrons 839Direct Current 839Bridge Circuits 841Alternating Curr
22、ent 844Solid-State Electronics 848Appendix 3 Basics of Chemistry 855Basic Definitions 855Valence 856Symbols, Formulas, and Equations 857Molecular Formulas and Percentage Composition 858Inorganic Chemistry 860Organic Chemistry 862Index 865ixPrefaceReaders will wonder how the second edition of this bo
23、ok on fundamentals can be published when there already seems to be so much similar material on the market. This one truly continues to be different. As the introductory volume to the entire Practical Guide Series, it was written in the PGS spiritwith emphasis on the practical. This isnt always easy
24、to do when dealing with fundamental concepts. The contributors to this book have succeeded, however, in finding the right balance between requisite theory and recommended application.Another way in which this book is different is that it has a proven track record. Before becoming the introductory vo
25、lume to the Practical Guide Series, it was used in a preliminary version as reference notes for an introductory course in process instrumentation given at McGill University in Montral. This course has run continuously for more than 50 years, and the lecturers have always been practitioners. Their ba
26、ckgrounds have rubbed off on the course presentations andfortunatelyin this book.Finally, this book was written by a dedicated group of professionals, many of whom are members of the Montral chapter of ISA. A major factor in assembling all the material needed to produce the words as they are printed
27、 here was the commitment and enthusiasm of all the contributors. The reader will undoubtedly sense this throughout the book.PrefacexAbout the EditorDonald A. Coggan, author of ISAs book and accompanying software, Preparing for Instrumentation Technician Evaluation, is an independent consulting engin
28、eer. Since 1981, he has carried on his business activities under the umbrella company, Donald A. Coggan, Ingnieur-Engineer. With a value-engineering orientation and particular specialty in laboratory ventilation control, he has provided English and French services throughout the United States and Ca
29、nada, as well as overseas.Born and raised in Winnipeg, Manitoba, Don later moved to Montral where he obtained his Bachelor of Electrical Engineering degree from McGill University. Before starting up his own consulting engineering business at the end of 1980, Don had previously worked for Johnson Con
30、trols and MCC Powers in positions of increasing responsibility. In addition, he was a part-time instructor from 1972 to 1986 at Vanier College where he taught courses in instrumentation, HVAC controls, energy conservation, and computer-aided drafting.Don is the author of over 60 articles and technic
31、al papers, which he has presented throughout North America and in Europe and Asia. As founder and Editor-in-Chief of Gaining Control, his own technical publications company serving the control and automation industry, he has written a number of technical reports and software programs. An avid reader
32、 and amateur health buff, Don lives and works in Outremont, Qubec.xiContributorsBiographies of each of the following contributors are included at the end of their respective chapters.Helen BeecroftLafarge Corporate Technical ServicesDiana Churchill BouchardPulp and Paper Research Institute of Canada
33、Gilles J. P. BouchardConsultantJames E. BouchardJohnson thus, the measured quantity may be disturbed by the act of measurement, making a perfect measurement theoretically impossible. Good instruments are de-signed to minimize this effect.Energy Conversion Principles Energy Controlling PrinciplesElec
34、tromagnetic ResistancePiezoelectric InductanceMagnetostrictive (as a generator) CapacitanceThermoelectric Mechanoresistance (strain)Photoelectric MagnetoresistancePhotovoltaic ThermoresistanceElectrokinetic PhotoresistancePyroelectric PiezoresistanceMagnetorestrictive (as a variable inductance)Hall
35、effectRadioactive ionizationRadioactive screeningIonization (humidity in solids)Figure 1-2. Generalized Description of an InstrumentSensors4The output signal of the primary sensing element is a physical variable, such as displacement, voltage, or current. For the instrument to perform the desired fu
36、nction, it may be necessary to convert this variable to another, more suitable variable while preserving the information content of the original signal. An ele-ment that performs such a function is called a variable-conversion element. Note that while not every instrument needs a variable-conversion
37、 element, some require several. Also, the “elements” referred to here are functional elements, not physical elements.In performing its intended task, an instrument may require that a signal repre-sented by some physical variable be manipulated in some way. Manipulation means a change in numerical va
38、lue, according to some definite rule while preserv-ing the physical nature of the variable. Thus, an electronic amplifier accepts a small voltage signal as input and produces an output signal that is also a voltage but is some constant times the input. An element that performs such a function will b
39、e called a variable-manipulation element.When the functional elements of an instrument are physically separated, the data must be transmitted from one to another. The data transmission element per-forms this function. It may be as simple as a shaft and bearing assembly, or it may be as complex as a
40、complete telemetry system.If the information about the measured quantity is to be communicated to a hu-man being for purposes of monitoring, control, or analysis, it must be put into a form that is recognizable by one of the human senses. The data presentation ele-ment performs this “translation” fu
41、nction. This element may involve a simple pointer moving over an indicating scale or a pen moving over a recording chart.These elements are present in the pressure-type thermometer (see Figure 1-3). The liquid-filled bulb acts as primary sensor and variable-conversion element be-cause a temperature
42、change results in a pressure change within the bulb due to the constrained thermal activity of the filling fluid. This pressure converts pressure to displacement. This displacement is manipulated by the linkage and gearing to give a larger pointer motion. A scale and pointer again serve to present o
43、r communicate the data.TerminologyInstrument engineering has its own terminology. Some of the terms have sub-tle meanings, and a misunderstanding can lead to a completely mistaken impres-sion of a systems performance. The following definitions are intended only as an introduction to the use of the t
44、erminology. For more complete and precise defini-tions refer to the ISA standard ANSI/ISA-51.1-1979 (R1993) Process Instru-mentation Terminology.RANGEThe region between the limits within which a quantity is measured, received, or transmitted, expressed by stating the minimum value (lower range value
45、) and maximum value (upper range value). Every sensor is designed to work over a specified workable range. While an electrical output may be adjusted to suit the application, this is not usually practical with mechanical transducing elements. The design ranges of these mechanisms are usually fixed,
46、and exceeding them can permanently damage a sensor. Transducing elements must be used over the part of their range in which they provide predictable performance and often truer linearity.ZEROA measurement must be made with respect to a known datum. Often, it is con-venient to adjust the output of th
47、e instrument to zero at the datum. For example, the output of a Celsius thermometer is zero at the freezing point of water; the out-Introduction to Sensor Fundamentals5put of a pressure gage may be zero at atmospheric pressure. Zero, therefore, is a value ascribed to some defined point in the measur
48、ed range.ZERO DRIFTOne of the problems that occurs with sensors is when the value of the zero signal varies from its set value. This introduces an error into the measurement that may be equal to the amount of variation, or drift, as it is usually termed. All sen-sors are affected by drift to some ex
49、tent, which is sometimes specified in terms of short-term and long-term drift. Short-term drift is usually associated with changes in temperature or electronics stabilizing. Long-term drift is usually associated with aging of the transducer or electronic components.SENSITIVITYSensitivity of a sensor is defined as the change in output of the sensor per unit change in the parameter being measured. Sensors may have constant or variable sensitivities, in which cases they are described as having a linear or a nonlinear output, respectively. Clearly, the greater the output signal ch
