Chap 01 Introduction to Measurements Final - Made Easy · Contact: 011-45124612, 0-9958995830, 8860378007 Visit us at: ... Chap_01_Introduction to Measurements_Final.pmd Author: windows-98

Comprehensive Theory

with Solved Examples and Practice Questions

Electronic Measurements and Instrumentation

ElectronicsEngineering

MADE EASY Publications

Corporate Office: 44-A/4, Kalu Sarai (Near Hauz Khas Metro Station), New Delhi-110016E-mail: [email protected]: 011-45124612, 0-9958995830, 8860378007

Visit us at: www.madeeasypublications.org

Electronic Measurements and InstrumentationCopyright ©, by MADE EASY Publications.All rights are reserved. No part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photo-copying, recording or otherwise), without the prior written permission of the above mentioned publisher of this book.

First Edition: 2015First Edition: 2016 (Revised and Updated)

© All rights reserved by MADE EASY PUBLICATIONS. No part of this book may be reproduced or utilized in any form without the written permission from the publisher.

This book was motivated by the desire to further the evolution of a concise book

on Electronic Measurements and Instrumentation. Keeping in focus

the importance of this subject in GATE and ESE, we have done a proper study

and thereafter developed the content of the book accordingly. This edition has

an expanded discussion of all relevant topics in the subject.

Initially, we compiled the perceptions of our students on their problems

in GATE and ESE while dealing with the questions from this subject. We

identified their various problems like- lack of fundamentals of the subject,

difficulty in solving simple questions, shortage of a complete study package, etc. These strengthened

our determination to present a complete edition of Electronic Measurements and Instrumentation textbook.

The book addresses all the requirements of the students, i.e. comprehensive coverage of theory, fundamental

concepts, objective type problems and conventional problems, articulated in a lucid language. The concise

presentation will help the readers grasp the concepts with clarity and apply them with ease to solve problems

quickly. The book not only covers the entire syllabus of GATE and ESE, but also addresses the need of many other

competitive examinations. Topics like ‘introduction to measurements, electromechanical indicating instruments,

errors in measurement and their analysis, methods of reducing residual inductance and capacitance in resistors,

measurement of energy and power, measurement of resistance, A.C. bridges, digital instrumentation, cathode

ray oscilloscope, transducers’, are given full coverage in line with our research on their importance in competitive

examinations.

We have put in our sincere efforts to present elaborate solutions for various problems, different problem solving

methodology, some useful quick techniques to save time while attempting MCQs without compromising the accuracy

of answers. A summary of important points to remember is added at the end of each topic. For the convenience of

the readers, points to remember are specifically highlighted in the form of a note- both in theory as well as solved

examples. At the end of each chapter, sets of practice question are given with their keys, that will allow the readers

to evaluate their understanding of the topics and sharpen their problem solving skills.

Our team has made their best efforts to remove all possible errors of any kind. Nonetheless, we would highly

appreciate and acknowledge if you find and share with us any printing, calculation and conceptual error.

It is impossible to thank all the individuals who helped us, but we would like to sincerely thank all the authors, editors

and reviewers for putting in their efforts to publish this book.

With Best Wishes

B. Singh

CMD, MADE EASY

Preface

Chapter 1Introduction to Measurements .............. 2 1.1 Measurements and it’s Significance ....................... 2

1.2 Basic Block Diagram of Measurement System.... 2

1.3 Static Characteristics of Instrument and

Measurement Systems ................................................ 3

1.4 Dynamic Characteristics of Instrument

and Measurement Systems ....................................... 6

1.5 Errors in Measurements and their Analysis .......... 7

1.6 Types of Errors ..............................................................11

1.7 Statistical Treatment of Data ...................................12

1.8 Standard and their Classifications .........................19

1.9 Important Prefixes and Their Symbol ..................21

Student Assignments-1 ...............................................22

Student Assignments-2 ...............................................22

Chapter 2Electromechanical Indicating Instruments ............................................25 2.1 Introduction ..................................................................25

2.2 Deflection and Null Type Instruments .................26

2.3 Torques in Electromechanical Indicating

Instruments ...................................................................28

2.4 Types of Damping .......................................................30

2.5 PMMC Instruments .....................................................32

2.6 Errors in Meters ............................................................42

2.7 Moving Iron (M.I.) Instruments ...............................43

2.8 General Torque Equation of Moving Iron

Instruments ...................................................................44

2.9 Errors in Moving Iron Instruments ........................45

2.10 Electrodynamometer Type Instruments .............56

2.11 Applications of Electrodynamometer Type

Instruments ...................................................................58

2.12 Rectifier Type Instruments (or Rectifier Meters) ... 71

Student Assignments-1 ...............................................76

Student Assignments-2 ...............................................77

Chapter 3Measurement of Power and Energy .....81 3.1 Introduction ..................................................................81

3.2 Measurement of Power in DC Circuits .................81

3.3 Measurement of Power in AC Circuit ...................82

•ElectrodynamometerWattmeter

•ErrorinElectrodynamometerWattmeters

•LowPowerFactorWattmeter

3.4 Power in Poly Phase Systems ..................................95

3.5 Measurement of Energy ........................................ 102

Student Assignments-1 ............................................ 111

Student Assignments-2 ............................................ 111

Chapter 4Measurement of Resistance and DC Bridge ......................................114 4.1 Resistors ....................................................................... 114

4.2 Methods of Reducing Residual Inductance and

Capacitance in Resistors ........................................ 115

4.3 MeasurementofLowResistance ........................ 117

•Ammetervoltmetermethod(orV-Imethod)

•Kelvindoublebridgemethod

•Potentiometermethod

(iv)

Electronic Measurements and Instrumentation

Contents

4.4 Measurement of Medium Resistance ............... 126

•Ammeter-voltmetermethod(orV-Imethod)

•Substitutionmethod

•Wheatstonebridgemethod

•Ohmmetermethod

4.5 Important Definitions ............................................. 132

4.6 Measurement of High Resistance ...................... 137

•LossofChargeMethod

•Meggar

•DirectDeflectionMethod

•MegaohmBridge

Student Assignments-1 ............................................ 141

Student Assignments-2 ............................................ 142

Chapter 5A.C. Bridges ..........................................144 5.1 Introduction to Bridge Measurement

and A.C. Bridges ........................................................ 144

5.2 Measurement of Inductance ................................ 151

•Maxwell’sBridge

•Hay’sBridge

•Anderson’sBridge

•Owen’sBridge

5.3 Measurement of Capacitance .............................. 166

•Desauty’sBridge

•ScheringBridge

5.4 WagnerEarthingDevice ........................................ 169

5.5 MeasurementofFrequency(Wein’sBridge) .... 173

5.6 Special Bridge circuit .............................................. 176

•CarryFosterSlideWireBridge

•HeavisideMutualInductanceBridge

Student Assignments-1 ............................................ 178

Student Assignments-2 ............................................ 179

Chapter 6Digital Instrumentation and Signals Analysis ............................182 6.1 DigitalVoltmeters(DVM) ....................................... 182

•RamptypeDVM

•IntegratingtypeDVM

•PotentiometricTypeDVM

6.2 DigitalFrequencyMeter ........................................ 187

6.3 Digital Phase Meter ................................................. 188

6.4 Signals Analysis ......................................................... 189

•Waveanalyzer

•Harmonicdistortionanalyzer

•Spectrumanalyser

6.5 HarmonicDistortionAnalyzer ............................. 191

6.6 SpectrumAnalyzer .................................................. 194

Student Assignments-1 ............................................ 195

Student Assignments-2 ............................................ 196

Chapter 7Cathode Ray Oscilloscope (CRO) ........199 7.1 BasicsofCRO(CathodeRayOscilloscope) ...... 199

7.2 AdvantagesofCRO .................................................. 199

7.3 Cathode Ray Tube (CRT) ........................................ 201

7.4 DeflectionSensitivityofCRO ............................... 204

7.5 Graticule ...................................................................... 205

7.6 Relation Between Bandwidth and Rise Time ... 206

7.7 LissajousPattern ....................................................... 208

7.8 PhaseAngleFromtheLissajousPattern .......... 212

7.9 SpecialCRO ................................................................ 214

7.10 ProbesofCRO ............................................................ 214

Student Assignments-1 ............................................ 215

Student Assignments-2 ............................................ 216

Chapter 8Transducers ..........................................218 8.1 Introduction ............................................................... 218

8.2 Active and Passive Transducers ........................... 219

8.3 Analog Transducers ................................................. 219

8.4 Measurement of Displacement using

Transducers ................................................................ 220

•Potentiometer

•Linearvariabledifferentialtransformer(LVDT)

•Halleffecttransducer

8.5. Strain Gauges............................................................. 227

8.6 Piezo-electricTransducers .................................... 229

8.7 Inductive Transducers............................................. 235

8.8 Capacitive Transducers ........................................... 236

8.9 Photoelectric Transducer ....................................... 237

(v)

(vi)

8.10 Measurement of Temperature ............................. 239

•ResistanceThermometer(RTD)

•Thermistors

•ApplicationofThermistors

•Thermocouples

•Pyrometer

•Bimetallicstrip

8.11 Measurement of Pressure...................................... 249

8.12 MeasurementofFlow ............................................. 255

8.13 Measurement of Sound ......................................... 259

8.14 Measurement of Angular Displacement .......... 260

Student Assignments-1 ............................................ 263

Student Assignments-2 ............................................ 263

Chapter 9Miscellaneous ......................................266 9.1 Potentiometer ........................................................... 266

9.2 QualityFactorMeter(QMeter) ........................... 271

9.3 FluxMeter ................................................................... 276

9.4 Data Acquisition System ........................................ 277

9.5 Telemetry .................................................................... 280

Student Assignments-1 ............................................ 281

Student Assignments-2 ............................................ 281

nnn