This document discusses electrical and electronic measurement. It begins with an outline covering measurement and its significance, methods of measurement, classification of instruments, errors in measurement, accuracy and precision, significant figures, and standards of measurement. Measurement is defined as the process of converting physical parameters to meaningful numbers by comparing an unknown quantity to a standard unit. Instruments are then broadly classified as mechanical, electrical, or electronic. Methods of measurement are direct or indirect, and instruments can be absolute or secondary, deflection or null type, and used for indicating, recording, or controlling. Sources of error in measurement include gross, systematic, and random errors. Accuracy refers to closeness to the true value while precision refers to the closeness of repeated measurements. Significant

1. Electrical and Electronic Measurement
Parveen Malik
Assistant Professor
School of Electronics Engineering
KIIT University
parveen.malikfet@kiit.ac.in
July 3, 2019
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 1 / 33

2. Outline
1 Measurement and its significance
2 Methods of Measurement
3 Classification of instruments
4 Errors in measurement
5 Accuracy and Precision
6 Significant Figures
7 Standards of Measurement
8 IEEE Standards
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 2 / 33

3. Measurement
” I often say that when you can measure what you are speaking about and
can express in numbers, you know something about it; when you can-not
express it in numbers your knowledge is a meagre and Unsatisfactory Kind
” - Lord Kelvin
Measurement1is the process by which one convert physical parameters to
meaningful numbers. Measuring process is the one in which the property
of an object or system under consideration is compared to an accepted
standard unit.
Requirement of Measurement
The standard used for comparison must be accurately defined and
commonly accepted.
e.g Heavy or light weight doesn’t have sense until its compared with a
standard.
The apparatus used and method adopted must be provable.
1
A Course in Electrical and Electronic Measurements and Instrumentation,
A. K. Sawhney, Dhanpat Rai.
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 3 / 33

4. Measurement and its significance

5. Measurement and its significance
Significance
Measurement play a significant role in achieving goals and objective
of engineering because of feedback information supplied by them. e.g.
Each branch of engineering have two functions :
Design of equipment and process,
Proper operation and maintenance of equipment and process.
All these process require measurements.
Applications
Monitoring of Process and Operations.
Control of processes and operations.
Experiment Engineering Analysis.
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 5 / 33

6. Methods of Measurement

7. Methods of measurement
Methods of Measurement
Direct Method
1 Unknown quantity is directly
compared against a primary
or secondary standard. e.g.
Length, Mass Measurement
2 Human Factor is more2.
3 Less Accurate
Indirect Method
1 Unknown quantity is
measured by instruments.
e.g. Measurement of strain
on elastic iron.
2 Human Factor is less.
3 More Accurate
(a) (b) (c) (d)
Figure: (a) Vernier Calliper (b) Micrometer (c) Multimeter (d) AM
2
Human preciseness =0.25 mm
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 7 / 33

8. Methods of Measurement
What is Instrument ?

9. Methods of measurement- Instrument
Instrument
An instrument is a physical device used to measure the unknown quantity
or variable.
Broader Classification - Electrical, electronic and Mechanical.
Earlier instruments were mechanical in nature and their principals of
operating is vogue today.
Three essential elements of an instrument which are still valid today
are
Detector
An
Intermediate
Transfer Device
Indicator
Recorder
Storage Device
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 9 / 33

10. Types of Instruments
Mechanical, Electrical and
Electronic Instruments

11. Types of Instruments - Broad Classification
Mechanical, Electrical and Electronic Instruments
Mechanical Instruments
Very reliable for static and stable conditions.
Unable to operate under dynamic and transient conditions.
Very bulky,rigid and heavy.
Produce a lot of Noise
Electrical Instruments
More rapid than Mechanical.e.g Galvanometer
Obey Ohm’s law
Limited time due to involvement of mechanical parts. e.g. Industrial
recorders response time 0.5 to 24s.
Frequency response
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 11 / 33

12. Types of Instruments - Broad Classification
Mechanical, Electrical and Electronic Instruments
Electronic Instruments
Faster response -Semiconductor devices (E.g Typical RT ≃ ns)
Higher Sensitivity- Can detect weaker signals e.g. Bio electric
potential ≃ 1mV
Greater Flexibility - Can be added with pre-amplifier to detect weak
signal
Lower weight
Higher Reliability- Can operated at adverse locations.
Low power consumption
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 12 / 33

13. Classification of Instruments
Absolute and Secondary

14. Classification of Instruments- Absolute and Secondary
Absolute Instruments
These instruments gives the
magnitude of quantity under
measurement in terms of physical
constants of the instrument.
e.g. Tangent Galvanometer3
Rayleigh’s current Balance4
Secondary Instruments
These instruments gives the
magnitude of quantity under
measurement by directly observing
the output. e.g. Voltmeter,
Glass Thermometer, Pressure
gauge5
(a) (b) (c) (d)
Figure: (a) T.G. (b) R.C.B. coils (c) Pressure Gauge (d) Voltmeter
3
http://www.questtutorials.com
4
https://nistdigitalarchives.contentdm.oclc.org
5
https://www.grainger.com
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15. Classification of Instruments
Deflection and Null Type

16. Classification of Instruments- Deflection and Null Type
Deflection Type
Basis of measurement is
deflection
e.g. PMMC
Null Type
Basis of measurement is Null
Indication
e.g. D.C.Potentiometer
(a) (b)
Figure: (a) Deflection Type - PMMC. (b) Null Type - D.C. Potentiometer
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17. Classification of Instruments - Deflection and Null Type
Comparison
Deflection Type
1 Lower Accuracy due to
calibration dependency on
instrument constants.
2 Less Sensitive as detector
need to measure magnitude
of unknown quantity.
3 Suitable for Dynamic
Conditions
Null Type
1 Higher Accuracy due to
standard calibration.
2 More sensitive as detector
need not to measure
magnitude of unknown
quantity.
3 Suitable for Static
Conditions6.
6
Exception : Self Balancing Potentiometer used in commercial automatic
control instruments
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18. Classification of Instruments
Indicating, Recording and
Controlling

19. Classification of Instruments - Indicating, Recording and
Controlling Function
Indicating
Supply Info. as
an indication.
e.g Deflection of
pointer of
speedometer,
Pressure Gauge
Recording
Disseminate info.
in the form of a
record. e.g.
Potentiometer
records temp.
put its
instantaneous
values on strip
chart recorder.
Controlling
Use info to
control the
original measured
quantity. e.g.
Thermostats -
Temperature
control, Floats -
liquid control.
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20. Errors in measurement
Gross , Systematic and Random

21. Errors in measurement7
- Gross , Systematic and Random
Gross Error
Human Errors
Misreading,
Adjustments
Improper application of
instruments,
computational
mistakes.
e.g Low R voltmeter in
high R applications
Systematic Error
Instrumental -
Overloading,irregular
spring tension, uneven
stretching of spring.
Environmental -
change in ambient
Temp., Humidity, Pres-
sure,Electrical/Magnetic
field.
Random Error
Random variations
in parameters or
system of
measurement.
Different results
for repeated
measurements.
(a) (b) (c)
7
Modern Electronic Instrumentation and Measurement Techniques - A .D
Helfrick, W.D. CooperParveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 21 / 33

22. Errors in measurement8
8
Lecture Notes on Electrical Engineering Technologies - Prof. Dr. Bahattin
KaragzoluParveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 22 / 33

23. Errors in measurement
Absolute Error and Relative Error

24. Errors in Measurement9
- Absolute Error and Relative Error
Absolute Error
When the measured value is expressed with a absolute value of error, then
it is refered to as Absolute Error
e.g R = 500 ± 50Ω. Here 50Ω is an absolute value.
Relative Error
When the error is expressed as a percentage or fraction of total measured
value.
e.g R = 500 ± 10%Ω. Here 10% is tolerance value in Resistance.
Another representation is ppm.
e.g. Temp. coefficient is expressed as ∆R
∆T = 100ppm/◦C. So 1MΩ would
have 100Ω of increment with 1◦C rise in temperature.
9
Electronic Instrumentation and Measurements David A. Bell
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25. Accuracy and Precision

26. Accuracy and Precision
Accuracy
It is the degree of closeness by
which the measured value
approaches the true value.
e.g True Value : −45.002◦C
Observation 1-5
:−44.93◦C,−44.99◦C,−44.90◦C,
−44.97◦C,−45.003◦C.
Factors Affecting Accuracy
Intrinsic Accuracy of
instrument
Accuracy of observer.
Variation of Signal under
measurement.
Precision
It is the degree of closeness by
which the measured values are
close to each other in a set of
observation.
e.g.
Observation 1-5 : −44.00◦C,
−44.99◦C,−44.90◦C
,−44.97◦C,−45.003◦C
Factors Affecting Precision
Conformity - repeatability or
reproducibility
No. of the significant
numbers.
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27. Accuracy and Precision
Mathematically
Absolute accuracy is defined as maximum absolute deviation from true
value.
δ1 = True Value − Min.
δ2 = Max. − True Value
Absolute Accuracy = max{δ1, δ2}
Relative Accuracy(RA) = Absolute Accuracy
True Value
% Accuracy = RA × 100
(1)
Precision is the absolute max. deviation from the average of the readings.
δ1 = Vavg − Min.
δ2 = Max. − Vavg
Precision = max{δ1, δ2}
(2)
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 27 / 33

28. Significant Figures

29. Significant Figures
Significant figures convey actual information regarding the magnitude and
the measurement precision of a quantity.
The more significant figures the greater the precision of measurement.
e.g. Let us consider the reading of voltmeter is 8.135 V. It means reading
is precise to 4 significant figures so that measurement precision is 0.001 V
or 1 mV. If the measurement was made to precision of 10mv, the display
would be 8.13 V or 8.14 V.
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 29 / 33

30. Standards of Measurement

31. Standards of Measurement
1 International Standards are defined by international agreement. and
maintained at international bureau of weights and measure.
International Ohm: It is defined as the resistance offered by a column
of mercury having a mass of 14.4521 grams, uniform cross-section
areas length of 106.300 cm, to the flow of constant current at the
melting point of ice.
International Ampere: It is an unvarying current, which when passed
through a solution of silver nitrate in water deposits silver at the rate
0.00111800 grams/sec (g/s).
2 Primary Standard are maintained by national standards laboratories
in different parts of the world.
3 Secondary Standard are used in industrial measurement laboratories.
4 Working Standard are the principle tools of a measurement .
Parveen Malik (PhD, IIT Guwahati) E and EM July 3, 2019 31 / 33

32. IEEE Standards

33. IEEE Standards
IEEE stands for Institute for Electrical and Electronics Engineers
This standard is mentioned by society named as IEEE standard.
Most of IEEE standard is considered as the standard test method for
testing and evaluating various electronic systems and components.
e.g. IEEE 488 Instrumentation Bus
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