ELECTRICAL INSTRUMENTATION

ANDPROCESS CONTROL

Dr. J.P. NavaniB.Tech., M.Tech., Ph.D.

Er. Sonal SapraB.Tech., M.Tech.

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As per new and revised syllabus of UPTU 2014-2015

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© 2015, Dr. J.P. Navani & Er. Sonal SapraAll rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) without written permission of the copyright owner. Any breach of this will entail legal action and prosecution without further notice.Jurisdiction : All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New Delhi, India only.First Edition 2015ISBN : 978-93-848-5740-0 Code : 1010 655 This book is for Sale in India & other SAARC Countries only.

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DedicatedTo

Shri Suresh Kumar Sapra

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Preface

Disclaimer : While the authors of this book have made every effort to avoid any mistakes or omissions and have used their skill, expertise and knowledge to the best of their capacity to provide accurate and updated information, the authors and S. Chand do not give any representation or warranty with respect to the accuracy or completeness of the contents of this publication and are selling this publication on the condition and understanding that they shall not be made liable in any manner whatsoever. S.Chand and the authors expressly disclaim all and any liability/responsibility to any person, whether a purchaser or reader of this publication or not, in respect of anything and everything forming part of the contents of this publication. S. Chand shall not be responsible for any errors, omissions or damages arising out of the use of the information contained in this publication.Further, the appearance of the personal name, location, place and incidence, if any; in the illustrations used herein is purely coincidental and work of imagination. Thus the same should in no manner be termed as defamatory to any individual.

It is a matter of great pleasure to present the first edition of the book Electrical Instrumentation and Process Control. The primary purpose of this book is to provide the students with the basic principles of Electrical Instrumentation and Process Control. It will serve as a textbook for the subject of Electrical Instrumentation and Process Control for B.E./B.Tech., Diploma and AMIE students of all branches.

This book is written in a simple and easy-to-understand language to explain the fundamental concepts of the subject. The book presents the subject of EIPC in a comprehensive manner to the students at undergraduate level.

This book not only covers the entire scope of the subject but also explains the philosophy of the subject. This makes the understanding of the subject more clear and interesting. The book will be very useful not only to the students but also to the faculty members.

Any suggestions for the improvement of the book will be acknowledged and well appreciated.

Dr. J.P. Navani Er. Sonal Sapra

(v)

Acknowledgements

From the core of our hearts, we would like to express our deep gratitude and thanks to all those who helped us directly and indirectly to reduce failure. We wish to express our profound thanks to all those who helped in making this book a reality. We express gratitude and special thanks to all those sources, i.e. teachers, colleagues, staff, students, reference books and journals which helped us in preparation and bringing out this book.

We are very grateful to Shri Dinesh Goel Ji (Chairman, RKG Group), Prof. B.K. Gupta (Adviser, RKG Group), Dr. Laxman Prasad, Dr. Neeta Awasthy, Dr. Rakesh Goel, Shri Vipul Goel, Dr. N.K. Sharma, Dr. Somshekher, Dr. S.C. Gupta, Dr. Manorma Sharma, Dr. Sanjay Garolla, Dr. Bhavesh Chauhan, Dr. A.K. Vasisth, Prof. Ravi Gupta and Prof. Neeraj Kumar who have always encouraged and helped us.

We are very thankful to all HODs, faculty members and staff of RKGIT and RKGITW, Ghaziabad. We also reserve our thanks to Prof. Reshu Gupta, Prof. Kadambari Aggarwal, Prof. J.G. Yadav, Mr. Mayank Goel, Mr. Sandeep Singh, Mr. Amit Yadav, Ms. Reema Malik, Mr. Anubhav Kumar, Mr. Alok Tyagi, Mr. Atul Kushwaha, Mr. Arun Vasisth, Mrs. Bindu Kapoor and all faculty members of RKGITW.

We are especially grateful to Mr. Shailesh Kumar, Mr. Manoj Kumar, Mr. Akhlish Kumar, Mr. Vikas Rajput, Mr. Varun Singhal, Mr. Madhur Chauhan, Mr. Rajnesh Sharma, Mrs. Isha Rajput and all faculty members of RKGIT.

We are also very thankful to Miss Kirti and Abhinaya for providing new and latest data.

We are also grateful and thankful to Master Midhansh, Ms. Megha Sapra and Mr. Pratek Kadam (Senior System Software Analyst), New Jersey, U.S.A.

Last but not least, we wish to thank the management and the editorial team of S. Chand & Company Pvt. Ltd., New Delhi for help and support in publication of this edition.

Dr. J.P. Navani Er. Sonal Sapra

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Syllabus

ELECTRICAL INSTRUMENTATION AND PROCESS CONTROL (NEE-403)

SECOND YEAR STUDENTS (2014-2015)UPTU (LUCKNOW)

UNIT – I TRANSDUCER – I Definition, Advantages of electrical transducers, Classification, Characteristics, Factors

affecting the choice of transducers, Potentiometers, Strain gauges, Resistance thermometer, Thermistors, Thermocouples, LVDT, RVDT.

UNIT – II TRANSDUCER – II Capacitive, piezoelectric, Hall effect and optoelectronic transducers. Measurement of motion,

force, pressure, temperature, flow and liquid level.

UNIT – III TELEMETRY General telemetry system, Landline & radio frequency telemetering systems, Transmission

channels and media, Data receiver & transmitter.

DATA ACQUISITION SYSTEM Analog data acquisition system, Digital data acquisition system, Modern digital data acquisition

system.

UNIT – IV

DISPLAY DEVICES AND RECORDERS Display devices, Storage oscilloscope, Spectrum analyzer, Strip chart & X-Y recorders,

Magnetic tape & digital tape recorders.

PROCESS CONTROL Principle, Elements of process control system, Process characteristics, Electronic, pneumatic

& digital controllers.

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ELECTRICAL INSTRUMENTATION AND PROCESS CONTROL (EEN-701 / EEE- 504)

FINAL YEAR STUDENTSUPTU (LUCKNOW)

UNIT – I TRANSDUCER – I Definition, Advantages of electrical transducers, Classification, Characteristics, Factors

affecting the choice of transducers, Potentiometers, Strain gauges, Resistance thermometer, Thermistors, Thermocouples, LVDT, RVDT.

UNIT – II TRANSDUCER – II Capacitive, piezoelectric Hall effect and optoelectronic transducers. Measurement of motion,

force, pressure, temperature, flow and liquid level.

UNIT – III TELEMETRY General telemetry system, Landline & radio frequency telemetering systems, transmission

channels and media, receiver & transmitter.

DATA ACQUISITION SYSTEM Analog data acquisition system, Digital data acquisition system, Modern digital data acquisition

system. UNIT – IV

DISPLAY DEVICES & RECORDERS Display devices, Storage oscilloscope, Spectrum analyzer, Strip chart & X-Y recorders,

Magnetic tape & digital tape recorders.

RECENT DEVELOPMENTS Computer aided measurements, fibre optic transducers, micro sensors, smart sensors, smart

transmitters.

UNIT – V PROCESS CONTROL: Principle, elements of process control system, process characteristics, proportional (P),

integral (I), Derivative (D), PI, PD and PID control modes. Electronic, Pneumatic & digital controllers.

(viii)

Contents 1. TRANSDUCER-I 1–49 1.1 Introduction 1 1.2 Transducer versus Sensor 2 1.3 Types of Transducer 3 1.4 Basic Requirement of a Transducer 4 1.5 Classification of Transducer 5 1.6 Characteristics of Transducer 6 1.7 Factors Affecting Choice of Transducer 6 1.8 Mechanical Devices as Primary Sensing Elements 7 1.9 Resistive Transducer 14 1.10 Potentiometer 14 1.11 Strain Gauge 21 1.12 Temperature Transducer 27 1.13 Resistance Thermometer (Resistance Temperature Detector) 28 1.14 Thermistor 31 1.15 Thermocouple 33 1.16 Inductive Transducer 38 1.17 Linear Variable Differential Transformer (LVDT) 39 1.18 Rotary Variable Differential Transformer (RVDT) 43 1.19 Load Cell 43

2. TRANSDUCER-II 50–107 2.1 Introduction 50 2.2 Capacitive Transducers 51 2.3 Piezoelectric Transducer 55 2.4 Hall Effect Transducer 59 2.5 Optoelectronic/Photoelectronic Transducer 62 2.6 Measurement of Motion 68 2.7 Measurement of Force 68 2.8 Measurement of Pressure 70 2.9 Classification of Pressure 71 2.10 Low and Medium Pressure Measurement 72 2.11 High Pressure Measurement 75 2.12 Vacuum Gauges 77 2.13 Measurement of Temperature 81 2.14 Methods of Temperature Measurement 81 2.15 Measurement of Flow 86 2.16 Different Types of Flow Meters 88 2.17 Measurement of Liquid Level 96

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3. TELEMETRY AND ACQUISITION SYSTEM 108–139

3.1 Introduction 108 3.2 Methods of Data Transmission 109 3.3 Telemetry 109 3.4 General Telemetry System 110 3.5 Types of Telemetry System 110 3.6 Modulation Methods in R.F. Telemetry System 116 3.7 Types of Modulation 116 3.8 Demodulation 119 3.9 Multiplexing in Telemetering System 119 3.10 Frequency Modulation (FM) Telemetry System 122 3.11 Pulse Telemetry System 122 3.12 Problems in Telemetry System 125 3.13 Transmission Channels and Media 125 3.14 Types of Transmission Channel and Media 126 3.15 Data Acquisition System 127 3.16 Types of Data Acquisition System 128 3.17 Classification of Data Acquisition System 131 3.18 Modern Digital Data Acquisition System 134 3.19 Block Diagram of Modern Digital Data Acquisition System 135 3.20 Data Loggers 135 3.21 General Purpose Interface Bus (GPIB) or IEEE-488 137

4. DISPLAY DEVICES AND RECORDERS 140–202

4.1 Introduction 141 4.2 Display Devices 142 4.3 Light Emitting Diode (LED) 142 4.4 Liquid Crystal Display (LCD) 146 4.5 LED versus LCD 147 4.6 Dot Matrix Display 148 4.7 Summary of Display Devices 152 4.8 Applications of Digital Display 153 4.9 Cathode Ray Oscilloscope (CRO) 154 4.10 Cathode Ray Tube (CRT) 156 4.11 CRO Measurement 158 4.12 Storage Oscilloscope 160 4.13 Signal Analysis 163 4.14 Wave Analyser 164 4.15 Harmonic Distortion Analyser 167 4.16 Spectrum Analyser 171 4.17 Recorders 176

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4.18 Graphic Recorders 177 4.19 Strip Chart Recorder 178 4.20 Oscillographic Recorders 184 4.21 Magnetic Tape Recorder 185 4.22 Digital Tape Recorder 192 4.23 Digital Frequency Counter 193 4.24 Analog and Digital Data Converters 196

5. PROCESS CONTROL 203–234

5.1 Introduction 203 5.2 Control System 203 5.3 Principles of Process Control 204 5.4 Types of Process Control 204 5.5 Elements of Process Control System 205 5.6 Properties of Controller 206 5.7 Classification of Controllers 207 5.8 Analog Controllers 217 5.9 Electronic Controller 218 5.10 Pneumatic Controllers 225 5.11 Pneumatic Controller versus Hydraulic Controller 230 5.12 Digital Controller 230

6. RECENT DEVELOPMENTS 235–256

6.1 Introduction 235 6.2 Computer Aided Measurement 236 6.3 Microprocessors or Microcomputers Used in DAS 236 6.4 Modern Digital Data Acquisition System 237 6.5 Block Diagram of Modern Digital DAS 237 6.6 Data Loggers 238 6.7 Block Diagram of Data Loggers 238 6.8 IEEE-488 Standard/General Purpose Interface Bus (GPIB) 239 6.9 Optical Fibre Sensors 241 6.10 Micro Sensors 243 6.11 Smart Sensors 245 6.12 Sensors and Their Applications 247 6.13 Recent Trends in Sensor Technology 248 6.14 Smart Transmitters 249 6.15 Programmable Logic Controller (PLC) 250

UNIVERSITY PAPERS 257–270

CHAPTER

1

OUTLINE 1.1 Introduction 1.11 Strain gauge 1.2 Transducer versus sensor 1.12 Temperature transducer 1.3 Types of transducer 1.13 Resistance thermometer 1.4 Basic requirement of a transducer 1.14 Thermistor 1.5 Classification of transducer 1.15 Thermocouple 1.6 Characteristics of transducer 1.16 Inductive transducer 1.7 Factors affecting choice of transducer 1.17 Linear Variable Differential Transformer (LVDT) 1.8 Mechanical devices as primary sensing 1.18 Rotary Variable Differential elements Transformer (RVDT) 1.9 Resistive transducer 1.19 Load cell 1.10 Potentiometer

OBJECTIVESAfter completing this chapter, you will be able to: ● Understandtheconceptoftransducerandsensor. ● Knowthevarioustypesoftransducer. ● Understandthealltypesoftransducerveryeasily. ● Explainthealltypesoftransducerofthischapter.

1.1 INTRODUCTION An electronic instrumentation system consists of a number of components to perform a measurement andrecorditsresult.ThebasicmeasurementsystemconsistsofthreevitalcomponentsasshownintheFig.1.1. (a) Inputdevice (b) Processingdevice (c) Outputdevice

Input device Processing device Output device

Fig. 1.1. The input device receives the quantity under measurement and delivers a proportionalor analogous electrical signal to the processing device.Here the signal is amplified, filtered orotherwisemodifiedinformatacceptabletotheoutputdevice.

1

Transducer-I

2 ELECTRICAL INSTRUMENTATION & PROCESS CONTROL

Usuallytheinputquantityformostoftheinstrumentationsystemisa“non-electricalquantity.”In order to use electricalmethods and techniques formeasurement, the non electrical quantityisgenerallyconverted intoanelectrical formbyadevicecalleda transducer.Wecandefineatransducer as adevice which convert a physical quantity (non electrical) into an electrical signal’s. The primary objective of process control is to control the physical parameters such astemperature,pressure,flowrateetc.Thesystemusedtomaintaintheseparameterconstant,closeto somedesired specificvalue is calledProcess Control System.Theseparametermaychangebecauseofinternalandexternaldisturbanceshenceaconstantcorrectiveactionisrequiredtokeeptheseparameterconstantorwithinthespecifiedrange.

1.2 TRANSDUCER VERSUS SENSOR

Aswehavediscussedabovethatatransducersisadevicewhichconvertsaphysicalquantityintoanelectricalsignal.Theelectricalsignalproducedmaybeavoltage,currentorfrequency.Atransducerusesmanyeffectstoproducesuchconversion.Theprocessoftransformingsignalfromoneformtoanotherformiscalledtransduction. Theelectricaltransducerconsistsoftwopartswhichareverycloselyrelatetoeachother.Thetwo parts are: (i)Sensingordetectingelement (ii)Transductionelement Thesensingordetectingelementiscommonlyknownassensor. Sensor: Sensor is a device that produces a measurable response to a change in physicalcondition. Transduction Element:AtransductionelementtransformstheoutputofasensingelementintoanelectricaloutputasshowninFig.1.2.

Sensingelement

Transductionelement

Sensorresponse

Electrical

signal

Non-electrical

quantity

Fig. 1.2. Transducer elements in cascade

The common range of an electrical signal used to represent analog signal in the industrialenvironmentis0to5Vor4to20mA.Inindustrialapplications,nowadays,4to20mArangeismostcommonlyusedtorepresentanalogsignal.Acurrentof4mArepresentsazerooutputandcurrentof20mArepresentsafullscalevaluei.e.,5Vincaseofvoltagerepresentation. Definition: Different views exist over commondefinitionofbothsensorsandtransducers.Asaresultdifferent definitions have been adopted for an easydistinction. “A device which converts a physical quantity into the proportional electrical signal is called Transducers.”

OR “Instrument society of America defines a sensor or transducer as a device which provides a usable output in response to a specified measurand.”

OR “An element that senses a variation in input energy to produce a variation in another or same form of energy is called a sensor whereas a transducer uses transduction principle to convert a specified measurand into usable output.”

Do You Know

Instrument society of America (ASI) was founded in 1945.

TRANSDUCER-I 3

The transducers are widely used inindustrial application, instrumentationsystem and measurement work becauseall quantities that need to be measured,cannot be displayed as easily as others.A better measurement of a quantity canusuallybemadeifitmaybeconvertedtoanotherformwhichismoreconvenientlyor accurately displayed. For Example,manometer which detects pressure andindicates itdirectlyona scalecalibratedinactualunitsofpressure. Thusthetransducerisadevicewhichprovidesausableoutputinresponsetospecificinputmeasurandwhichmaybephysicalormechanicalquantity,propertyorcondition.Thetransducermaybe mechanical, electrical, magnetic, optical, chemical, acoustic, thermal, nuclear or a combination ofanytwoormoreofthesemanyatimes,thetransducerisapartofacircuitandworkswithotherelementsofthatcircuittoproducetherequiredoutput.

1.3 TYPES OF TRANSDUCER [UPTU : 2007-08, GBTU : 2009-10]

Weknow thata transducer is adevice that receivesenergy fromone systemand transmits it toanothersystemindifferentform.BasicallytherearetwotypesoftransducersasshownintheBlockDiagram1.1.

Transducers

Electricaltransducers

Mechanicaltransducers

Block Diagram 1.1

1.3.1 Electrical TransducersThe function of converting non electrical quantity into electrical quantity is accomplished by adevicecalledelectricaltransducer.Basicallyanelectricaltransducerisasensingdevicebywhichaphysical,Mechanicaloropticalquantitytobemeasuredistransformeddirectlyintoanelectricalsignal(current,voltageorfrequency). Mostquantitiestobemeasuredarenonelectricalsuchastemperature,pressure,displacementetc. but these quantities cannot bemeasured directly. Hence such quantities are required to besensedandchangedintosomeformforeasymeasurement.Theelectricalquantitiessuchascurrent,voltage, resistance, Inductance and capacitance can be conveniently measured, transferred andstoredthereforeformeasurementofnonelectricalquantitiesthesearetobeconvertedintoelectricalquantitiesfirstandthenmeasured.Theproductionofthesesignalisbaseduponelectricaleffectswhichmayberesistive,inductiveandcapacitiveinnature.

Advantages Thereareanumberoftransducerswhichtransformavarietyofphysicalquantitiesintoelectricalsignals.Theadvantagesofconvertingphysicalquantitiesintoanalogouselectricalquantitiesareasfollows: 1. Theelectricaloutputofthetransducercanbeeasilyusedtransmittedandprocessedforthe

purposeofmeasurement.

Fig. 1.3. Transducers and sensors

4 ELECTRICAL INSTRUMENTATION & PROCESS CONTROL

2. Itreducestheeffectsoffrictionandothermechanicalnonlinearities. 3. Duetotheintegratedcircuittechnologytheelectricalandelectronicsystemsarecompact

andhavinglessweightandportable. 4. Thereducedeffectsofmassinertiaproblems. 5. Theelectricalsignalscanbeeasilyattenuatedoramplified. 6. Thepowerrequirementoftransducersisverysmall.Theelectricalsystemscanbecontrolled

withasmalllevelofpower. 7. Theeffectsoffrictionareminimised. 8. Theoutputcanbeindicatedandrecordedremotelyatadistancefromthesensingmedium.

Disadvantages 1. Theelectricaltransducersarecostly. 2. Thedesigniscomplicated. 3. Theeffectofageinganddriftsmustbeconsidered.

GOOD TO KNOW Themaindisadvantageofanelectricaltransducerisitscostandwhiledesigningthecircuit,theeffectofageinganddriftsofparametersofactivecomponentsmustbeconsidered.Thismakesthedesigncomplicated.

1.3.2 Mechanical TransducersThemechanical transducers are those primary sensing elements that respond to changes in thephysicalconditionofasystemandgivesoutputindifferentform.Forexample,whenabimetallicstrip issubjected toa temperaturechange then theoutput is themechanicaldisplacementof thestrip.Themechanicaltransduceraredistinguishedfromtheelectricaltransduceronthebasisoftheoutputsignalgenerated.Themechanicaltransducer’sgenerateoutputsignalwhichismechanicalbynature.Theelectricalsignalrespondtonon-electricalquantitiesbutgenerateoutputsignalwhichiselectricalbynature.Itispracticallyalwayspossibletouseeithermechanicalorelectricaltransducerfor the measurement of any physical parameter. But practically for each measurand electricaltransducerarepreferedoverthemechanicaltransducers.

1.4 BASIC REQUIREMENT OF A TRANSDUCER TheTransducersshouldmeetthefollowingbasicrequirements. 1. Ruggedness:Itshouldbecapableofwithstandingoverloadandsomesafetyarrangement

shouldbeprovidedforoverloadProtection. 2. Linearity: Its input-output characteristics shouldbe linear and it shouldproduce these

characteristicsinsymmetricalway. 3. Repeatability:Itshouldreproducesameoutputsignalwhenthesameinputsignalisapplied

againandagainunderfixedenvironmentalconditionse.g.,temperature,pressure,humidityetc. 4. High output signal quality:Thequalityofoutputsignalshouldbegoodi.e., the ratio of the

signaltothenoiseshouldbehighandtheamplitudeoftheoutputsignalshouldbeenough 5. High Reliability and stability: Itshouldgiveminimumerrorinmeasurementfortemperature

variations,vibrationsandothervariouschangesinsurroundings. 6. No Hysteresis: Itshouldnotgiveanyhysteresisduringmeasurementwhileinputsignalis

variedfromitslowvaluetohighvalueandvice-verse. 7. Residual Deformation: Thereshouldbenodeformationonremovalofinputsignalafter

longPeriodofapplication. 8. Operating Range: Theoperatingrangeofthetransducershouldbewidetopermititsuse

underawiderangeofmeasurementconditions.

Electrical Instrumentation And ProcessControl

Publisher : SChand Publications ISBN : 9789384857400Author : Dr. J. P. Navani,Er. Sonal Sapra

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