A Course in Electrical and Electronic Measurements and Instrumentation

1351 Pages·2012·167.63 MB·English

by  A.K. Sawhney, Puneet Sawhney

A Course in
Electrical
and
Electronic Measurements
and
Instrumentation
A.K. Sawhney
M.Sc. (Engg.)
Formerly Professor & Head,
Electrical and Electronics Engineering Deptt.,
Thapar Institute of Engineering and Technology,
(Deemed University) PATIALA - 147004
Puneet Sawhney
M.Sc.
University of Waterloo, Canada
Senior Engineer, Engineering Global Solutions
DEARBORN (U.S.A)
DHANPAT RAI & Co. (Pvt.) Ltd.
EDUCATIONAL AND TECHNICAL PUBLISHERS
A Course in
Electrical and Electronic Measurements and Instrumentation
Published by : GAGAN KAPUR
Dhanpat Rai & Co. (P) Ltd., Delhi
Sales Office : Regd. Office :
1682, 1710, Nai Sarak, 4576/15, Agarwal Road
Delhi-110006 Darya Ganj, New Delhi-110002
Phone : [phone] Phone : [phone], 37, 38
[email protected] [email protected]
© All Rights Reserved
Edited by : Smt. Chandra Kanta Sawhney
Disclaimer
Every effort has been made to avoid errors or omissions in this publication. Inspite of this, some errors
might have crept in. Any mistake, error or discrepancy noted may be brought to our notice which shall be
taken care of in the next edition. It is notified that neither the publisher nor the author or seller will be
responsible for any damage or loss of action to any one, of any kind, in any manner, therefrom.
Editions : 1973, 1976, 1981, 1983, 1987, 1988, 1989, 1990,
1991, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2007
Nineteenth Revised Edition : 2011
Reprint: 2012
Price : 495
Typesetting by : North Delhi Computer Convention, Delhi-110009, [email protected]
Printed at : Natraj Offset, Delhi
Preface to t^e Nineteenth Edition
The authors are pleased to bring out the nineteenth edition of the book Electrical and
Electronic Measurements and Instrumentation', and are grateful to students and
faculty members of different institutions in India and abroad for their warm
affectionate support.
The book has been completely reproduced and care has been taken to rectify the
mistakes which had cropped up in the earlier editions. The authors take this
opportunity to thank all those who were kind enough to send critical suggestions for
the improvement of the text.
The present edition retains all the features of the earlier editions. A new salient
feature of the book is, addition of Five New Chapters (Chapters 32 to 36) at the end of
the book. The authors hope that with these additions, the book covers all the topics
required in the syllabus and that the students and practising engineers need to
familiarise themselves with the present day technology and practice in the area of
Electrical and Electronic Measurements and Instrumentation.
The authors are highly obliged to Mrs. Chandra Kanta Sawhney for editing the present
edition.
Authors again request the students, teachers and practising engineers to send their
suggestions for updating the text.
A.K. Sawhney
Puneet Sawhney
Preface To T^e Fourth Edition
The author is pleased to bring out the Fourth Edition of the book and is thankful to
both teachers and students for their affectionate and warm reception to the third
edition of the book which has been sold out in a period of less than one year. The
present edition retains essentially the same subject-matter as the third edition.
However, the typographical and other errors, which had crept in earlier edition, have
been corrected.
The book is intended as a standard text for students studying for their first degree in
Electrical, Electronics and Instrumentation Engineering at Indian Universities and
abroad, and also for those appearing for A.M.I.E. Section B and other professional
examinations. The book is equally useful for postgraduate students as well as
practising engineers involved in the field of Measurements and Instrumentation.
There have been significant changes in curriculum of almost all the universities in
recent years. Electrical and Electronic Instrumentation is now offered as separate
paper in many universities. This has been necessitated on account of latest
technological advances which put greater emphasis and reliance on Electronic
Instrumentation.
The contents of the book have been drastically modified, re-arranged and updated to
acquaint the reader of modern trends in the field of Measurements and Instrumentation.
The book has been divided into two Parts. Part I deals with Measurements and
Measuring Instruments and Part II takes care of the Instrumentation. There is an
extensive coverage of Electrical and Electronic Instrumentation in this edition of the
book as compared with the earlier ones. The coverage of Instrumentation portion is
about 500 pages out of a total of nearly 1200 pages. The subject of Instrumentation
has been developed in logical steps. Separate chapters are devoted to topics like
Generalized Measurement Systems, Transducers, Signal Conditioning, Data
Transmission and Telemetry, Display Devices and Recorders, Measurement of
Non-electrical Quantities and Data Acquisition Systems. Also there are additional
chapters on static and dynamic characteristics of Measurement Systems. There is an
increased emphasis on digital instruments and instrumentation which is consonant
with the present trends.
Conversions from various systems of units to S.I. units is given as Appendix at the end
of the book. The significant additions to the measurements portion are Transformer
ratio bridges (which are fast replacing the conventional four arm a.c. bridges),
spectrum analyzer, vector impedance meter, vector voltmeter, digital maximum
demand indicator and Hall effect multiplier to name a few.
The book in fact covers a very wide spectrum of the field of Electrical and Electronic
Measurements and Instrumentation and is a complete reference in itself.
Another outstanding feature of the book is the inclusion of over 400 solved problems
which in addition to linking the theory with actual applications gives an insight of the
industrial practice. Also about 300 unsolved problems {with answers) have been
included to give the students practice in solving problems.
The author considers the inclusion of problems on Instrumentation (both solved and
unsolved) as a speciality of this book. This is a pioneering effort which is the outcome
of author's experience of teaching the subject for almost two decades.
The book though voluminous, covers two papers, i.e., first on Electrical and Electronic
Measurements and Instruments and second on Electrical and Electronic Instrumentation
and thus fully justifies its volume. SI units have been uniformly used in the book
throughout.
The author will feel highly obliged to all readers for their constructive suggestions and
healthy criticism of the book which will go a long way in the improvement of the text.
The author is thankful to his wife, Chandra, for rendering assistance in the compilation
and editing of the work.
The author is grateful to his brother Ravish and Ajay for their constant help during the
preparation of the text.
To author's parents who have been a source of encouragement and guidance.
A. K. Sawhney
Contents
Part I
Electrical and Electronic Measurement and Measuring Instruments
Measurements and Measurement Systems
1
1.1 Measurements 1 1.9 Functions of Instruments and
1.2 Significance of Measurements 1 Measurement Systems 6
1.5 Methods of Measurements 1 1.10 Applications of Measurement Systems 6
1.3.1 Direct Methods 1 1.11 Types of instrumentation Systems 7
1.3.2 Indirect Methods 2 1.12 Information and Signal Processing 7
1.4 Instruments and Measurement Systems 2 1.15 Elements of a Generalized
1.5 Mechanical, Electrical and Measurement System 7
Electronic Instruments 2 1.13.1 Primary Sensing Element 8
1.5.1 Mechanical Instruments 2 1.13.2 Variable Conversion Element 8
1.5.2 Electrical Instruments 2 1.13.3 Variable Manipulation Element 8
1.5.3 Electronic Instruments 2 1.13.4 Data Presentation Element 9
1.6 Classification of Instruments 5 1.14 Input-Output Configurations of Measuring
1.7 Deflection and hull Type Instruments 5 Instruments and Measurement Systems 10
1.7.1 Deflection Type 4 1.14.1 Desired Inputs 10
1.7.2 Null Type 4 1.14.2 Interfering Inputs 10
1.7.3 Comparison of Deflection and Null 1.14.3 Modifying Inputs 10
Type Instruments 5 1.15 Methods of Correction for
1.8 Analog & Digital Modes of Operation 5 Interfering and Modifying inputs 12
/ hapter 2 CHARACTERISTICS OF INSTRUMENTS AND MEASUREMENT SYSTEMS
19
2.1 Measurement System Performance 19 2.12.5 Noise Factor and Noise Figure 24
2.2 Static Calibration 19 2.15 Accuracy and Precision 26
2.5 Static Characteristics 19 2.13.1 Accuracy 26
2.13.2 Precision 26
2.4 Errors in Measurement 19
2.5 True Value 20 2.14 Indications of Precision 27
2.6 Static Error 20 2.15 Significant Figures 27
2.16 Range of Doubt or Possible Errors
2.7 Static Correction 20
and Doubtful Figures 28
2.8 Scale Range and Scale Span 21
2.17 Static Sensitivity 29
2.9 Error Calibration Curve 21
2.18 Linearity 50
2.10 Reproducibility and Drift 21
2.19 hysteresis 51
2 11 Repeatability 22
2.20 Threshold 52
2 12 hoise 22
2.12.1 Signal to Noise Ratio (S/N) 22 2.21 Dead Time 52
2.12.2 Sources of Noise 23 2.22 Dead Zone 55
2.12.3 Johonson Noise 24 2.25 Resolution or Discrimination 55
2.12.4 Power Spectrum Density 24 2.24 Loading Effects 55
2.25 Input and Output Impedances 55 2.27 Loading Effects due to Series
2.25.1 Input Impedance 34 Connected Instruments 58
2.25.2 Input Admittance 34 2.28 Generalized Impedance and
2.25.3 Output Impedance 34 Stiffness Concepts 59
2.25.4 Output Admittance 35
2.29 Static Stiffness and Static Compliance 40
2.26 Loading Effects due to 5hunt
2.50 Impedance Matching and Maximum
Connected Instruments 55
Power Transfer 42
hapter 3 ERRORS IN MEASUREMENTS AND THEIR STATISTICAL ANALYSIS 49
Limiting Errors (Guarantee Errors) 49 3.10.2 Arithmetic Mean 58
^.3.2 Relative (Fractional) Limiting Error 49 3.10.3 Measure of Dispersion from the Mean 58
Combination of Quantities 3.10.4 Range 58
with Limiting Errors 50 3.10.5 Deviation 58
3.10.6 Average Deviation 58
X 5.4 Known Errors 55
3.10.7 Standard Deviation (S.D.) 59
Types of Errors 54
3.10.8 Variance 59
"re Gross Errors 54
3.10.9 Normal or Gaussian Curve of Errors 59
Systematic Errors 54 3.10.10 Precision Index 60
3.7.1 Instrumental Errors 54 3.10.11 Probable Error 61
3.7.2 Environmental Errors 56 3.10.12 Average Deviation for the Normal Curve 61
3.7.3 Observational Errors 56 3.10.13 Standard Deviation for the Normal Curve 61
Random (Residual) Errors 57 3.10.14 Probable Error of a Finite
Number of Readings 61
5.9 Central Value 57
3.10.15 Standard Deviation of Mean 62
5.10 Statistical Treatment of Data 57
3.10.16 Standard Deviation of Standard Deviation 62
3.10.1 Histogram 57
5.11 Probability Tables 62
Dynamic Characteristics of Instruments and
Measurement Systems 81
4.1 Dynamic Response 81 4.21 Differential Equation for a General
4.2 Dynamic Analysis of Measurement Systems 82 First Order System 97
4.5 Mathematical Models of Measurement Systems 85 4.22 Response of a First Order System to
4.4 Linear and Non-Linear Systems 85 a Unit Step Input 97
4.5 Analysis of Linear Systems 86 4.25 Modelling of a Thermometer 99
4.6 Linear Approximation of Non-linear Systems 86 4.24 Ramp Response of a First Order System 102
4.7 Electric Networks 87 4.25 Impulse Response of a First Order System 105
4.8 Mechanical Systems 88 4.26 Response of Second Order Systems 104
4.9 Force-Voltage and Force-Current Analogies 89 4.27 Step Response of a Second Order System 106
4.27.1 Time Domain Specifications 107
4.10 Thermal Systems 90
4.28 Ramp Response of a Second Order System 108
4.11 Liquid Level Systems 91
4.29 Impulse Response of a
4.12 Pneumatic Systems 92
Second Order System 110
4.15 Transfer Function 95
4.50 Frequency Domain Analysis 110
4.14 Block Diagram Representation 94
4.51 Frequency Response of First Order Systems 111
4.15 Impulse Response of a Linear System 94
4.52 Frequency Response of a
4.16 Sinusoidal Transfer Function 94
Second Order System 115
4.17 Time Domain Response 94
4.55 Dead-Time Elements 116
4.18 Zero Order Systems 95
4.54 Correlationship between Time and Frequency
4.19 First Order Electrical Systems 95 Response of Second Order Systems 117
4.20 First Order Non-electrical Systems 96
eight
7.5 Constructional Details 180 7.11.1 Eddy Current Damping Torque of
Metal Former 188
7.6 Types of Supports 181
7.11.2 Damping Torque of a Metal Disc 189
7.7 Torque/Weight Ratio 182
7.12 Permanent Magnets 190
7.8 Control Systems 183
7.13 Pointers and Scales 190
7.8.1 Comparison between Spring and
Gravity Control 184 7.14 Symbols used for Analog Instruments 191
7.9 Damping Systems 187 7.14.1 Safety 191
7.14.2 Nature of Measured Quantity and
7.9.1 Air Friction Damping 187
Number of Measuring Elements 191
7.9.2 Fluid Friction Damping 187
7.14.3 Position of Use 192
7.9.3 Eddy Current Damping 188
7.14.4 Accuracy Class 192
7.9.4 Electromagnetic Damping 188
7.14.5 Principle of Operation 192
7.10 Comparison of Methods of Damping 188
7.15 Recording Instruments 192
7.11 Methods of Eddy Current Damping 188
7.16 Integrating Instrument 195
apter 8 GALVANOMETERS 197
8.1 Introduction 197 8.12 Damping 204
8.2 D'Arsonval Galvanometer 197 8.15 Sensitivity 205
8.3 Construction of d'Arsonval Galvanometer 197 8.14 Galvanometer Shunts 206
8.4 Torque Equation 198 8.14.1 Ayrton Universal Shunt 207
8.5 Dynamic Behaviour of Galvanometers 198..> 8.15 Ballistic Galvanometer 214
8:5.1 Equation of Motion 199 8.15.1 Construction of Ballistic Galvanometers 215
8.5.2 Underdamped Motion of a 8.15.2 Theory of Ballistic Galvanometer 215
Galvanometer 200 8.15.3 Calibration of a Ballistic Galvanometer 217
8.5.2A Undamped Motion of a 8.16 Flux Meter 219
Galvanometer 201
8.16.1 Construction of Flux Meter 219
8.5.3 Critically Damped Motion of
8.16.2 Operation of Flux Meter 219
a Galvanometer 201
8.16.3 Theory of Flux Meter 219
8.5.4 Overdamped Motion of Galvanometer 202
8.16.4 Use of Shunt with Flux Meter 220
8.6 Response of Galvanometers 202
8.16.5 Advantages and Disadvantages
8.7 Operational Constants 202 of Flux Meters 221
8.8 Relative Damping 202 8.17 Vibration Galvanometers 224
8.9 Logarithmic Decrement 203 8.17.1 Construction of Vibration Galvanometers 225
8.10 Overshoot 205 8.18 Duddell's Oscillograph 227
8.11 tlon-dimensional Curves of 8.18.1 Theory Duddell's Oscillograph 228
a Galvanometer Motion 204
er 9 Analog Ammeters, Voltmeters and Ohmmeters 237
9.1 Introduction 257 9.4.7 Effect of Temperature Changes
9.2 Types of Instruments 257 in Voltmeters 246
9.5 Errors in Ammeters and Voltmeters 258 9.4.8 Multirange d.c. Voltmeters 246
9.4.9 Sensitivity of PMMC Voltmeters 247
9.4 Permanent Magnet Moving Coil
9.4.10 Sensitivity of PMMC Voltmeters
Instrument (PMMC) 258
and their Loading Effects 248
9.4.1 Construction of PMMC Instruments 238
9.4.11 Errors in PMMC Instruments 249
9.4.2 Torque Equation 240
9.4.12 Advantages and Disadvantages
9.4.3 Ammeter Shunts 241
of PMMC Instruments 249
9.4.4 Effect of Temperature Changes
9.5 Ohmmeters 250
in Ammeters 243
9.5.1 Series-type Ohmmeter 250
9.4.5 Multi-range Ammeters 244
9.5.2 Shunt Type Ohmmeter 252
9.4.6 Voltmeter Multipliers 245
9.6 Multimeter or Volt-Ohm-Milli-ammeter 9.12 Hot Wire Instruments 277
(V.O.M.) 255 9.15 Thermocouple Instruments 2.77
9.7 Ratiometer 255 9.13. 1 Principle of Operation of
9.7.1 Ratiometer Ohmmeters 256 Thermoelectric Instruments 278
9.8 Megger 256 9.13. 2 Construction of Thermoelectric
Instruments 278
9.9 Moving Iron (M.l.) Instruments 257
9.13. 3 Advantages and Disadvantages of
9.9.1 General Torque Equation of
Thermo-electric Instruments 280
Moving Iron Instruments 257
9.14 Electrostatic Instruments 282
9.9.2 Classification of Moving Iron
Instruments 258 9.14.1 Force and Torque Equations of
Electrostatic Instruments 282
9.9.3 Shape of Scale of Moving
9.14.2 Quadrant Electrometer 283
Iron Instruments 259
9.14.3 Kelvin Multicellular Voltmeter 285
9.9.4 Shunts for Moving Iron Instruments 260
9.14.4 Attraction Type Portable Electrostatic
9.9.5 Multipliers for Moving Iron
Instrument 285
Instruments 260
9.14.5 Attracted Disc Type-Kelvin
9.9.6 Comparison between Attraction and
Absolute Electrometer 286
Repulsion Types of Instruments 261
9.14.6 Extension of Range of Electrostatic
9.9.7 ^ Errors in Moving Iron Instruments 261
Voltmeters 286
9.9.8 Advantages and Disadvantages of
9.14.7 Advantages and Disadvantages of
Moving Iron Instruments 262
Electrostatic Instruments 287
9.10 Electrodynamometer (Eelectrodynamic)
9.15 Rectifier Type Instruments 291
Type Instruments 267
9.15.1 Rectifier Elements 292
9.10.1 Operating Principle of Electrodynamometer
9.15.2 Characteristics of Rectifier Elements 292
Type Instrument 268
9.15.3 Half Wave Rectifier Circuit 293
9.10.2 Construction of Electrodynamometer
Type Instrument 268 9.15.4 Full Wave Rectifier Circuit 293
9.10.3 Torque Equation of Electrodynamometer 9.15.5 Sensitivity of Rectifier Type
Instruments 269 Instruments 294
9.10.4 Electrodynamometer Ammeters 270 9.15.6 Extension of Range of Rectifier
Instruments as Voltmeters 294
9.10.5 Electrodynamometer Voltmeters 270
9.15.7 Factors Affecting the Performance of
9.10.6 Errors in Electrodynamometer
Rectifier Type Instruments 295
Instruments 271
9.15.8 Multimeters 297
9.10.7 Shape of Scale Electrodynamometer
Type Instruments 272 9.15.9 Simpson's Multimeter 298
9.10.8 Advantages and Disadvantages of 9.15.10 Rectifier Ammeters 299
Electrodynamometer Instruments 273 9.15.11 Advantages of Rectifier Instruments 299
9.11 Electrothermic Instruments 277 9.15.12 Loading Effects of Rectifier Instruments 299
9.11.1 Classification of Electrothermic 9.16 Summary Classification of Alternating
Instruments 277 and Direct Current Meters 500
Instrument Transformers 313
10.1 Introduction 515 10.5.6 Construction of Current Transformers 322
10.2 Use of Instrument Transformers 313 10.5.7 Clamp on Ammeters 323
10.5 Ratios of Instrument Transformers 515 10.5.8 Effect of Secondary Open Circuit 324
10 4 Burden of an Instrument Transformer 515 10.5.9 Permanent Magnetization and
Demagnetization of Cores of
10.5 Current Transformers 515
Current Transformers 324
10.5.1 Relationships in a
10.6 Potential Transformers 550
Current Transformer 316
10.6.1 Difference between C.T. and P.T. 330
10.5.2 Errors in Current Transformers 318
10.6.2 Relationships in a
10.5.3 Characteristics of Current Transformers 318
Potential Transformer 331
10.5.4 Causes of Errors in Current
10.6.3 Errors in Potential Transformers 333
Transformers 319
10.6.4 Reduction of Errors in
10.5.5 Means to Reduce Errors in
Potential Transformers 333
Current Transformers 319
ten
10.6.5 Construction of Potential Transformers 334 10.6.9 Characteristics of
10.6.6 High Voltage Potential Transformers 335 Potential Transformers 336
10.6.7 Protection of 10.7 Testing of Instrument Transformers 558
Potential Transformers 335
10.8 Testing of Current Transformers 558
10.6.8 Capacitive Potential Transformers 335
10.9 Testing of Potential Transformers 541
hapter 11 Measurement of Power and Wattmeters 351
U.l Power in D.C. Circuits 551 11.6 Thermocouple Wattmeter
U.2 Power in A.C. Circuits 551 (Thermal Watt Converter) 565
11.5 Electrodynamometer Wattmeters 552 11.7 Hall Effect Multiplier 565
11.3.1. Construction of Electrodynamometer 11.8 Measurement of Power using
Wattmeter 352 Instrument Transformers 565
11.3.2 Theory of Electrodynamometer
11.9 Power in Poly-Phase Systems 568
Wattmeters 353
11.10 Measurement of Power in
11.3.2A Shape of Scale of Electrodynamometer
Three Phase Circuits 568
Wattmeters 353
11.3.3 Errors in Electrodynamometer 11.11 Three Phase Wattmeters 571
Wattmeters 354 11.12 Measurement of Reactive Power 571
11.4 Ferrodynamic Wattmeters 562
11.5 Low Power Factor Wattmeters
(Electrodynamometer type) 562
apter 12 Measurement of Energy and Industrial Metering 379
12.1 General 579 12.7.9 Errors in Single Phase Energy Meters 387
12.2 Motor Meters 579 12.7.10 Adjustments in Single Phase Energy
Meters 387
12.5 Braking 579
12.8 Polyphase Energy Meters 588
12.4 Friction 580
12.8.1 Two Element Energy Meter 388
12.5 Energy Meters for A.C. Circuits 580
12.9 Industrial Metering and Tariffs 588
12.6 Theory of Induction Type Meters 580
12.10 Maximum Demand Indicators 589
12.7 Single Phase Induction Type Meters 582
12.10.1 Average Demand Indicator (Merz Price
12.7.1 Construction of Induction Type
Maximum Demand Indicator) 390
Energy Meters 382
12.7.2 Theory and Operation of 12.11 Measurement of Vah and VArh 591
Single Phase Energy Meters 383 12.12 VArh Metering 592
12.7.3 Lag Adjustment Devices 384 12.15 Measurement of Vah 595
12.7.4 Light Load or Friction Compensation 385
12.14 Testing of Energy Meters 596
12.7.5 Creep 386
12.14.1 Phantom Loading 396
12.7.6 Over-Load Compensation 386
12.14.2 Meter Testing Circuits 397
12.7.7 Voltage Compensation 387
12.7.8 Temperature Compensation 387
apter 13 MEASUREMENT OF PHASE AND FREQUENCY 405
13.1 Power Factor Meters 405 13.1.4 Advantages and Disadvantages of
13.1.1 Single Phase Electrodynamometer Moving Iron P.F. Meters 409
Power Factor Meter 405
15.2 Frequency Meters 410
13.1.2 Three Phase Electrodynamometer
13.2.1 Mechanical Resonance Type Frequency
Power Factor Meter 406
Meter (Vibrating Reed Type) 410
13.1.3 Moving Iron Power
13.2.2 Electrical Resonance Type
Factor Meters 407
Frequency Meters 411