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**Unformatted text preview: **A COURSE IN ELECTRICAL AND ELECTRONIC ~/IEASUREMENTS
AND
INSTRUMENrATIC>N . . ·. . . . By
A. K. SAWHNEY
M.Sc. (E11gg.)
Professor of Electrical E11gineeri11g
Tbapar Engineering College,
PATIA LA DHANPAT RAI & SONS
EDUCATIONAL AND T}tCHNICAL PUBLISHERS
1682, .Nai Sara~, Delhi-U0006
Phone : 265367 ~-· @All rights rese,frcd by, the author. No parts of this publication may be reproduced', stored in re;rieval .$ystem., ot·
transmitted, ibany.form or by a~y ~eans, elect~onic, mecha6ical, photocopying, recording, or o herwise, wi~h~~t
the prior wri~ten permissio.1 of the autho~.anJ the publisher.
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·. ·. By tbe Same ~uthor "· 1. A Course in Electrical Machine Design.
2. A Course in Mechanical Measurements and Instrumentation. First. E.aitjfn, 1 : 1973
S,etond F.d!tfon :.1976
: 1978
Reprint. \Rtprint
Reprint
.Third B/iition
Repriri/
Fburtij Editfon Reprinted·
, Reprint ,i'1• ·· . : 1979 : 1980
: 1981 (Modified and Enlarged).
: 1982
: '1983· 1984
1'85 I Compile~ b)' : Smt. ~hand~r Sawhney Pl,lblished by : J.C. Kapur', fqr Dhanpat Rai & Sons, Delbi"l10006 (H.o. JuUundur) ..
ctmposed by : Karan P1ibtio1·Sr.cv'ice, Subhash Park, Shahdara, Delhi·l1Qo3f.
Printed at 1. D.R., Prilltloj Service, Panch.sheeJ Garden, ShahdAta, DeJhH 10032/ I Preface to the· Fourtn 1:arc1on
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'The author i~ pleased to brfogi out the Fourth Editiori of the book a.ncf is _fhankful t~· both·
teachers and students for their affecfi-0nate and warm receptio:n to the thlfd ed1t~n of the boo~
whJ9h has been sold out in a period of less than one year. The present edit.ion retai~s essentially
the same subjectmatter as the third edition. However, the typographical and (\ther .errors,
which had crept in earlier edition, have been corre.cted.
The book is intended as a stand~rd text for students studying for their first de8ree i•.
Electrical, Electronics and lhstrumentation Engineering at ~ndian Universities (}nd abroad, qd·
also for those appearing for A.M.l.E. section Band other profession~l examinations. The book
is equally useful for postgraduate students as well as practising engineers involved in ihe iel4A
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of Measurements and Instrumentation.
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There have been significant changes in curriculum of almost all the upiversities in recent
years. Electrical and Electronic In,strumentation is now offered· as separate paper in maay
universitks. This has been necessitated on account of latest technological advances which put
greater emphasis and reliance on Electronic Instrumentation.
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The contents of the book have been· drastically modified, .re-arrange~ an9 updated t9 ·
acquaint the reader of modern trends in the field: pf_ Measurements and Instrumeµtation. _
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The bobk has b.een divided into two parts. -i Part I d~aJs with Mea.surements .and Measuriq
Instruments and Part II takes care of the Instrmnentat1on. There 1s an extensive coverage 4f
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 ahapteu
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 instrumftlnts and
instrumentation which is constant with the present trends.
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There are .three Appendices in the book. Appendix A deals with Number Systems,
Appendix B with Logic gates and Appendix C with conversions from various system~ of units to
S.I. The significant additions to the measurements· portion are Transformer ratio bridges (wliich
are fast replacing the conventional four arm a.c. bridges), spectrum analyzer, vector impedance
meter, vector meter, digital maximum demand indicator and Hall effect multiplier to name a few .
.The book ,in fact covers a very wide spectrum of the_Jield of Electrical and Electro1io
Measurements ?.nd Instrumentation and .is a conlplete reference in. itself.
Another outstanding feature of the book is the i~clusion Qf over 400 1solveQproblems which·
ill addition to linking the theory with actual applications gives
insight of the industrial practieo.
Also about 300 unsolved problems (with answers) have been included to give the students practiee
in solving problems.
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The author considers the inclusion of problems on Instrumentation (both· ''solved and uB.l
~~ved) as a speciality of this book. This is a pioneering effort which is the outcome of cuthor's,
experience of teaching the subject for almost two decades.
The book though voluminous, covers two papers, i.e., first on Electrical and Ele~tronie:
Measurements and Instruments and second on Electrical and Electronic Instrull_1entat\Qn .arid thus
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fully justifies its volume. SI units have been uniformly used in .the book throughout.
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The autho'r will feel highly obliged to·all the readers for their constructive suggestions aQd
healthy criticism of the book which will go a long way in the improvement of the text.
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The author is thankful to his wife, Chander J for render,ing assistance in the compilation Qd
editing of the work. ·
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The author is grateful to his brothers, Ravish a~d Ajay, for their constant help durinatlae:
p~eparatiQn of tqe text.
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To. . . aut~or;s parents who have ~~en~ s~urce of encourascment and guidance. an PATIALA 26-9-1.984 ' ~. A..K.
-· -- _.,.,,.,, ••>"' S.A.WQlf ' ' <" DEDICATED TO
Anuradha and Puneet 4', • ,I ., Chapt ' ,\ \,' Contents
PART I
ELECTRICAL. AND ELECTRONIC MEASUREMENTS ANO
MEASURING INSTRUMENTS
Chapter 1-Measurements and Measuring Systems ll-8 Measurements. Significance of Measurements Methods of Measurement.
Direct Methods. Indirec,t Methods .. Instruments. Mechanical, Electrical and ,
Electronic Jnstruments. Mec4anical .Instruments. Electrical . Instruments. Electronic Instruments.. Classification of Instruments: Analog and· Digital.
Modes ofc Operation. i Functions of Instruments and Measurement Sy.stems.
Applications of Measurement Systems. Elements of a Generalized Measurement Syste~. · ·
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Chapter 2 - Characteristics of Instruments and Measurement Systems 9-34 Measurement System J,>erformance. §tatic Calibration. Static Characteristics.
Errors in Measurements. True Value. Static Error. Static Correction.
Scale Range and Scale Span. Error Ca.libration Curve. Reproducibility
and Drift. RepeatabiJity. Noise. Accuracy and Precision. Indications
of Precision. Significant Figures. Range of Doubt or Possible Errors and
Doubtful Figures_. Static Sensitivity. Instrument Efficiency, ·Index·Scale
and Index Number. Linearity. Hysteresis. Threshold, Dead Time. Dead
Zone. Resolution or Discrimination. Loading , Effe~ts. Loading Effects
due to Shunt connected Instruments. Loading Effects due to s~ries connec·
ted Instruments. · Impedance Matching and Maximum Power Transfer.
Dynamic Response Measuiing Lag. Standard Signals, Overshoot. Unsol·
ved Problems.
Chapter 3-Errors in Measurements and their Statistical Analysis 35-'4 Limiting Errors (Guara'otee Errors). Relative (Fractional) Limiting ErrorL
Combination of Quantities with Limiting Errors · Known Errors.Types of
Errors. Gross Errors. Systematib Brrc,rs. In'strumental Errors. Environ·
mental Errors. Observational Errors. Random (Residual) Errors.. Central
,\/.'.
Value. Statistical , Treatment of Data. Histogram. Arithmetic Mean.
L~~r
Measure of Dispersion from the Mean. Range., Deviation. Average Devi·
· ation. Standard Deviation (S.D.), Variance. Normal or Gaussian Curve
of Errors. Precision fodex. Probable Error. Average Deviation for the
Normal Curve. Standard Deviatian for the Normal Curve. Probable
Error of a Finite Number of Readings. Standard Deviation of Mean.
Standard Deviation of Standard Deviation. Specifying ODDS. · Specifying
Measurement Data. Variance and Standard Deviations of Combination of
Components. Probable Error of Combination of Components. lJ'ncer·
tainty Analysis and Treatment of Single Sample Data : Propagation of
Uncertainties. Unsolved Probems.
Chapter 4-Units, Systems, Dimensions and Standards
65-q 101
Introduction. Unit. Absolute Units. Fundamental and Derkre.4 · Plcltts•.
Dime11sions. D!mepsi9ns ·of Me~hanical. 9. u~. ntities: ~istoric~l :Q.. a.pk.f. &r?,µp~ .
of System of Units. COS System .of Umts: Electromagnetic U~it( (~~¥P· .··~ ./ (it)
units). Electrostatic Units (e.s. u~its). Practical Units. Dimensional.Equations.
Dimensions in Electrostatic System. Dimensions in Electromagnetic System
Relationship between Electrostatic and Electromagnetic Systems of Units.
M.K.S. System (Giorgi System). Rationalised M.K.S.A. System. SI Units.
Base Units of SI. Supplementary Units. Multiplying Prefixes of 'Units
Determination of Absolute Units. Absolute Measurement of Current:
Rayleigh's Cu,rrent Balance. Absolute Measurement of Resistance: Loi'en7t
Method. Standards and their Classification : International· Standards;
Primary Stflndards. Secondary Standards. Working Standards., Standards
for Mass and Length. Atomic Frequency and Time Standards. Temperature
Standards. Luminons Intensity Standards. Electrical Standards. Emf.·
Standards : Primary Standard of Emf. Secondary Standn,rd of Bmf LaQo- ·
ratory Standards·of Emf. Higher Voltage Zener Sources and Temperature
Effects... Primary Standards of Resistance.. Current Standards. Inf. ilctanoo
Standards. Capacitance Standards. . Unsolved Problems.
1 Chapter 5 -Circuit Components (Rolstors, Inductors and Capacitors) and their Residues
Residues. Resistors. Resistance Materials. Spools (Formers) for ·coils
Resistance Wires. Ageing. Annealing. Resistance Standards. Resistance
Standards for. D.C. Low Resistance Standards. Stan·dard Resistances for
A.C. Circuits Frequency Errors of Resistors. Methods of Reducing Residual
.Inductance. Resistance Boxes. Thin Film Resistors. Composition Resistors
Shielded Resistors.
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INDUCTORS
Standards of Inductance. Formers for Inductance Coils. Coils of Induc·
tance Coils. Standards of Mutual lnouctance. Standards of Self-Inductance.
Vax:iable foduct1nces. Inductors for High Frequency Work. Inductors for
Low Frequency Work. Frequency Errors in Inductors.
CAPACITORS
Loss Angle and Power. Factor. Distributed Capacitance. Capacitance
Standards. Vacuum and Gas-filled Capacitors. Solid Dielectric Capacitors
Variable Capacitors. Decade Capacitance Boxes. Frequency Errors in
Capacitors. Unsolved Problems.
Chapter 6-Analog (pointer) Iostrnments
Analog Instruments. Classification of Analog Instruments. Principles of
Operation.
ELECTROMECHANICAL INDICATING
INSTRUMENTS
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Operating forces. Constructional Details. Types of Supports. Balancing.
Torque/Weight Ratio. Control Systems. Damping System&, Eddy Current
Damping Torque of M~tal Former. Damping Torque of a Metal Disc.
Permanent Magnets. Pointers and Scales. Recording Instruments. Integrat·
ing Instruments. Unsolved Problems. Chapter 7-GalvHometers
Introduction. D' Arsonval Galvanometer. Construciion of d'Arsonval
_Galvapometer. }'Qrque Equation. Dyna~i~ Behaviour pf Galvanometers.
Eqlia!ton of Motton. Underdamp.ed ¥ot1on. of a Galvanometer. Undamped
Motion of, a Galvanometer. CrittcaUy Damped Motion of a Galvanometer,
Operational Constants. Relative.Damping. , LogarithmicDoorement; Over- (
140~191 (iU) shoot. Overdamped Motion of Galvanpmeter. Non-dimensional Cur/ves
of a Galvanometer Motion. Damping. Sensitivity. Galvanometer· Ty~~·
Galvanometer Shunts. Ayrton Universal Shunt. Ballistic Gdlv.an.om ~.~r:·
Calibralion of a ·'Ballistic Galvanometer. Flux Meter. Use of Shunt . ith
.Flu!mete1'. Vibration Galvanometers. ·Duddell's Oscillograph. Unso ved
Problems.
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1 l£tiaptet.::s-Amdog Ammeters, Vo»tm~-~~r~ Hd Obmmete~s 192-~0 ·Introduction. Power Loss. Types of Instruments. Errors in Ammeters
and Voltmeters. Pamanent Magnet Moving Coil Instruments (PMMC)
Construction. Torque Equation.\ Range. Ammeter Shunts. Arrangement
-for Temperature Effect CorrectiQn. · Multi-range Ammeters Vottqieter
Multipliers. Effect of Temperatu~ Changes. Multirange d c. Voltmeters.
·Sensitivity. Voltmeter Sensitivity a~d Loading Effects. Errors. Advant~ges
and Disadvantages.
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Ohmmeters. Introduction. Series-tyP,e 0.hmmetel'/ Shunt type Ohmmete~s.
Multimeter or Volt-Ohm-Milli-ammeter (V.O.M.). Ratiometer. Ratiomet~r
Ohmmeters. Megger. Ducter Ohmmeter. . Moving Iron Instruments General Torque Equation .Cla~ifica·
. tion of Moving Iron Instruments. Attraction Typ~ ~epulsion
Type. Reason for Use on both A.C. and D.C. Shape bf Scale
.Long Scale Instruments. Shunt for Moving Iron Instruments. Multipliers
for Moving Iron I,nstruments. Comparison between Attraction and Repulsion ·
Types of Instruments. Errors. Advantages and Disadvantages. Electro·
dynamometer Electrodynamic) Type Instruments. Operating Principle
Construction. Torque Equation. Electrodynamometer Ammeters. Electrodyriamometer Voltmeters Errors. Use on D.C. and A.C. Shape Qf Scale.
Advantages and Disadvantages. Ranges . Use of Electrodynamoqieter Type
·Instruments at High Frequencies. Ferrodynamic Instruments. Construction
Operation. Advantages and DisadvaQ.tages Electrothermic Instrbments.
Classification Hot Wire Instruments. Thermoelectric Instruments. Thermal
Emf. Principle of Operation. Heater Element. Thermo-element Shape
of Scale Connections. Advantages and Disadvantages. Range's Electro~
static Instruments. Force and Torque Equations. Qu:idrant Electrometer
'Kelvin Multicellular Voltmeter. Attraction Type Portable Instruments.
Attracted Disc Type·Kelvin Ahsolute Electrometer. Everett Edgecumbe
Voltmeter. Use on both AC. and D.C· · Shape of Scale. General Con·
siderations Extension of Range of Electrostatic Voltmeters. Errors Advan. tages and Disadvantages. Inducti!ln Type Instruments. Principle of Operation.
Types of Instruments. Ferraris Type. ·Shaded Pole Type .. Shape of Scale.
Advantages and Disadvantages. R~ctifier Instruments. Rectifier Elements.
Rectifier Characteristics. Rectifier Voltmeters. Full Wave Rectifier Circuit~
Factors InfluenCing the Performance. Half Wave Rectifier Circuits. Multi·
meters. Simpson's Multimeter. Rectifier Ammeters. Advantages .of
Rectifier Instruments. Unsolved Problems. i Chapter 9- Instrumeo~ ·Transformers
Introduction. · Use of Instrument Transformers. Ratios. Burden. 289-332 CURRENT TRANSFORMERS Theory. Brron. Cbaract~risti~ of Curr~nt Tr41ntformers Causes of Errors.. ~,
Reduction of. Errors.· · Construction:: of · Currtnt 1'.ransforrners. Clamp .on
Aµimeters. E~ect of Seo()ndary Open Ci.-euit., r.inanel)t Magnetization and t .
'i ··~ (iv)
its Demagnetization. Current Transformers for High Frequencies. Potential
Transformers. Difference between C. T. and P. T. Theory. Errors. R,educ·
tion of Errors. Construction of Potential Transformers. High Voltage
Potential Transformers. Capacitive Potential Transformers Characteristics
of Potential Transformers. Testing of Instrument Transformers. Current
Transformer Testing. Potential Transformer.Testing. Unsolved Problems. ..1. 333-37~ Chapter IO-Measurement of Power and Wattmeters
Power in D.C. Circuits. Po~1er in: A.C. circuits. Electrodynamometer
Wattmeters. Construc'ion. Theory. Shape of Scale. Wa~tmeter Errors.
Torsii:m ·head Electrodyn amometer Watt meters Ferrodynamic ·Wattmeters.
Cambridge Reflecting Wattmeter Low Power Factor Wattmeters (Electro·
dynamameter type). Thermocouple Wattmeter (Thermal Watt Converter)
Electrostatic Wattmeters. Induction Type · Wattmeters. Lipman· Type
Induction Wattmeter. Hall Effect Multiplier. Measurement of Power Using
Instrument Tn;msfot·mers. Po\vcr ih Poly-Phase Systems. Measurement of
Power in Three Phase Circuits.
Three Phase Wattmeters. Measurerr .mt
of Reactive Power.· Summation ,Metering. Unsolved Problems. 3~1-403 Chapter H-Measureme'nt of Energy and Industrial Metering
General. Motor Meters Braking. Friction. Energy Meters for A.C.
Circuits. Single Phase Induction Type Watt-hour Meters. Construction.
Theory and Operation. Lag Adjustment Devices. Light Load or Friction
Compensation. Creep. Over-Load Compensation. Voltage Compensation.
Temperature Compensation. ·Errors. Adjustments. Polyphase Eoergy
Meters. Two Element Energy Meter. Industrial Metering and Tariffs
Maximum Demand Indicators. Measurement of VAh and VArh. VArh
Metering. Measurement of VAh. \ ENERGY METER TESTING
Types of T~sts. Phantom Loading. Testing 'Meth ·,ds. Meter Testing
Circuits Unsolved Problems.
tllQter 12 - Measurement of Phase and ;frequency 404--t23 POWER FAC'fOR METERS
Introduction. Single Phase Electrodynamometer Po·.ver Factor Meter, Three
Phase Electtodynamometer Power Factor Meter-Construction. ·Moving
Iron Power Factor. Meters. Rotating Field Power Factor Meter. Alternating Field Power Factor Meter (Nalder Lipman Type). Advantages and
Disadvantages of Moving Iron P.F. Meters.
FREQU~NCY METERS Types of Frequency Meters. · Mechanical Resonance Type Frequency Meter
(Vibrating Reed Type). Electrical Reasonance Type Frequency Meters.
Weston Frequency ·Meter. Ratiometer Type Frequency Meter. Saturable
Core Frequency Meter.
SYNCHROSCOJ: ,e;:,
. . : .,;'' Synchron;izing. Electro-dynamometer (Weston)Type Synchroscope. Moving
lron Synchroscopes. Pase Sequence Indicators.
· \'\ (v) Chapter 13-MelSorrement or Resistance
Classification of Resistances.
MEASUREMENT OF MEDIUM RESISTANCES I I~ ' Methods of Measurement of M.edium Resistances. Ammeter Voltmeter
Method. Substitution Method. Wheatstone· Bridge. Sensitivity of · Wheatstone Bridge. Galvanometer Current. Precisfon Measurement. of Medium
Resistances with Wheatston~ Bridge. Carey-Foster Slide-wire Bridge. Kelvin
Varley Slide. Limitations of Wheatstone Bridge.
MEASUREMENT OF LOW RESISTANCES
Introduction. Construction of Low Resistances. Methods for Measurement
of Low Resistance. Ammeter Vol1meter Method ..~Kelvin Double Btidge.
Kelvin Bridge Ohmmeter. · Unbalanced Kelvin Bridge.
MEASUREMENT OF HIGH RESISTANCES
Introduction. Difficulties· in Measurement of fligh Resistances~ Use of
Guard.Circuit. Methods
Measurement of High Resistance. Direct Deftec·
tion M,ethod. Loss of Charge Method. · Megohm Bridge Method. Measurement of Insulation Resistance with Power On. Unsolved Problems. for ~b1»1er 14-:-Potentlometers
. D.C. POTENfIOMETERS
Introduction. Basic Potentiometer Circuit. Laborhtory Type (Cro~pton'$)
Potebt~ometer. Multiple·Range Potentiometer. Cor.structional Details of
Potentiometers. Precision Type Potentiometers. Vernier Potentiometer.
Standard Cell Dial. True Zero. Brooks Deffectional Potentiometer. VoltRatio Box.. Application of D.C. Potentiometers: Protection of Standard
Cell and Galvanometer. Self-Balancing Potentiometers.
A.C. POTENTIOMETERS
Introduction. Standardidng of A C. Pote11tiometers · and Use t>f Transfer
Instruments. Types of A C. Potentiometers. Drysdale Polar Po(.Cniiometu.
Gall-Tinsley (co-ordinate type) A.C. Potentiometer. Quadrature Adjustments,
of Currents. Campbell· Larsen Potentiometer. Applications of A.C. Potentiometers Unsolved Problems, Chapter 15-Power System Measurements
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MEASUREMENT OF EARTH RESJSTANC~ 481-495 Necessity" of Earth. Biectrode. Necessity of Measurement of Resistante of
Earth Electrode. Factors Affecting Earth. Resistance. Methods of ~asuring.
Earth Resistance.
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LOCALIZATION OF CABLE FAULTS
Types of Faults Methods Used for Localizing Faults Methods· Used., for
Localizing Ground and sho1t Circuit Faults. Murray L0op Test. Varfoy
J.oop Test. Location of Open Circuit Faults in Cables.
SYMMETRIC{\L COMPONENTS ANO- THErR MBASUREMENT
Introduction to Symmctncal Comp'onen •.>. Ca;vul~tion of Symmetrical
_Conipon~nts M:easureinent of symmetrical tompon~nts; Measuremeat of
r·.-.., "' •,, (vi)
Positive Sequence Component of Current. Measurement of Negative Sequ·
ie!iJlce Component of Current. · Measuremen...

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