This document contains questions and answers related to electrical instrumentation and measurement systems. It discusses different types of instruments such as mechanical, electrical, and electronic instruments. It also addresses direct and indirect methods of measurement, instrument calibration, and applications of measurement systems. Various instruments are described including voltmeters, ammeters, wattmeters, and energy meters. Measurement methods such as potentiometers and instrument transformers are also summarized.

1. IMPORTANT QUESTIONS
Electrical Instrumentation
2 Marks Questions
Question What is meant by measurement?
Answer Measurement is an act or the result of comparison between the
quantity and a predefined standard.
Question What are the 2 methods for measurement?
Answer Direct method and
Indirect method.
Question Define Instrument.
Answer Instrument is defined as a device for determining the value or magnitude of a
quantity or variable.
Question List the types of instruments.
Answer The 3 types of instruments are
Mechanical Instruments
Electrical Instruments and
Electronic Instruments.
Question Classify instruments based on their functions.
Answer
Indicating instruments
Integrating instruments
Recording instruments
Question Give the applications of measurement systems.
Answer The instruments and measurement systems are sued for
Monitoring of processes and operations.
Control of processes and operations.
Experimental engineering analysis.
Question Why calibration of instrument is important?
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

2. IMPORTANT QUESTIONS
Answer The calibration of all instruments is important since it affords the opportunity to
check the instrument against a known standard and subsequently to errors in
accuracy.
Question Explain the calibration procedure.
Answer Calibration procedure involves a comparison of the particular instrument with
Either.
A primary standard
A secondary standard with a higher accuracy than the instrument to be calibrated
or An instrument of known accuracy.
Question Define Calibration.
Answer It is the process by which comparing the instrument with a standard to correct
the accuracy.
Question Name the different essential torques in indicating instruments.
Answer Deflecting torque
Controlling torque
Damping torque
Question Name the types of instruments used for making voltmeter and ammeter.
Answer PMMC type
Moving iron type
Dynamometer type
Hot wire type
Electrostatic type
Induction type.
Question State the advantages of PMMC instruments
Answer Uniform scale.
No hysteresis loss
Very accurate
High efficiency.
Question State the disadvantages of PMMC instruments
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

3. IMPORTANT QUESTIONS
Answer Cannot be used for ac m/s
Some errors are caused by temperature variations.
Question State the applications of PMMC instruments
Answer m/s of dc voltage and
Current used in dc galvanometer.
Question How the range of instrument can be extended in PMMC instruments.
Answer In ammeter by connecting a shunt resister
In voltmeter by connecting a series resister.
Question State the advantages of Dynamometer type instruments
Answer Can be used for both dc and ac m/s.
Free from hysteresis and eddy current errors.
Question State the advantages of Moving iron type instruments
Answer Less expensive
Can be used for both dc and ac Reasonably accurate.
Question State the advantages of Hot wire type instruments
Answer Can be used for both dc and ac Unaffected by stray magnetic fields
Readings are independent of frequency and waveform
Question What are the constructional parts of dynamometer type wattmeter?
Answer Fixed coil Moving Coil
Current limiting resister Helical spring
Spindle attached with pointer Graduated scale
Question Write down the deflecting torque equation in dynamometer type
wattmeter.
Answer Td á VI CosÖ
Question State the disadvantages of Dynamometer type wattmeter
Answer Readings may be affected by stray magnetic fields.
At low power factor it causes error.
Question Name the errors caused in Dynamometer type wattmeter.
Answer Error due to pressure coil inductance
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

4. IMPORTANT QUESTIONS
Error due to pressure coil capacitance
Error due to methods of connection
Error due to stray magnetic fields
Error due to eddy current.
Question How the errors caused by pc inductance is compensated.
Answer By connecting a capacitor in parallel to the resister.
Question How the errors caused by methods of connection is compensated
Answer By using compensating coil.
Question Name the methods used for power measurement in three phase circuits.
Answer Single wattmeter method
Two wattmeter method
Three wattmeter method.
Question What are the special features to be incorporated for LPF wattmeter?
Answer Pressure coil circuit
Compensation for Pressure coil current
Compensation for Pressure coil inductance.
Question Define Phantom loading.
Answer Method by which energizing the pressure coil circuit and current coil circuits
separately is called phantom loading.
Question State the use of phantom loading.
Answer Power loss is minimized.
Question Name the methods used in Wattmeter calibration.
Answer By comparing with std wattmeter.
By using voltmeter ammeter method.
By using Potentiometer.
Question What are the types of energy meters?
Answer Electrolytic meters
Motor meters.
Clock meters
Question Name the constructional parts of induction type energy meter.
Answer Current coil with series
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

5. IMPORTANT QUESTIONS
magnet Voltage coil with shunt
magnet Al disc
Braking magnet
Registering mechanism.
Question How voltage coil is connected in induction type energy meter.
Answer It is connected in parallel to supply and load.
Question How current coil is connected in induction type energy meter
Answer It is connected in series to the load
Question Why Al disc is used in induction type energy meter.
Answer Aluminum is a nonmagnetic metal.
Question What is the purpose of registering mechanism.
Answer It gives a valuable number proportional to the rotations.
Question What is the purpose of braking mechanism?
Answer It provides necessary braking torque.
Question Define creeping.
Answer Slow but continuous rotation of disc when pc is energized and cc is not
energized.
Question State the reason why holes are provided in Al disc.
Answer To avoid creeping holes are provided on both sides of Al disc.
Question What is the basic principle used in potentiometer
Answer In potentiometer the unknown emf is measured by comparing it with a std known
emf.
Question Name the potentiometer material used.
Answer In potentiometer the unknown emf is measured by comparing it with a std known
emf.
Question Name the potentiometer material used.
Answer German silver Manganin wire
Question Define standardization
Answer It is the process by which adjusting the current flows through the potentiometer
coil to make the voltage across the std cell is equal.
Question State the applications of potentiometer.
Answer Used for m/s of unknown emf Used for ammeter calibration Used for Voltmeter
calibration Used for wattmeter calibration
Question State the advantages of crompton potentiometer
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

6. IMPORTANT QUESTIONS
Answer More accurate Easy to adjust
Question What are the practical difficulties in ac potentiometers?
Answer More complicated
Accuracy is seriously affected
Difficulty is experienced in standardization.
Question Classify ac potentiometers
Answer Polar potentiometer
Coordinate potentiometer.
Question How the phase angle is measured in polar type potentiometers.
Answer Polar potentiometer
Coordinate potentiometer.
Question How the phase angle is measured in polar type potentiometers.
Answer It is measured from the position of phase shifter.
Question Name some ac potentiometers.
Answer Drysdale Tinsley potentiometer Gall Tinsley
potentiometer
Question State the advantages of ac potentiometers
Answer Can be used for m/s of both magnitude and phase angle
Can be used for m/s of inductance of the coil. It is used in m/s of errors in CTS
Question State the applications of ac potentiometers
Answer M/s of self inductance.
Ammeter calibration
Voltmeter calibration
Wattmeter calibration.
Question State the advantages of instrument transformers
Answer Used for extension of range Power loss is minimum
High voltage and currents can be measured.
Question State the disadvantage of instrument transformers
Answer Cannot be used for dc measurements.
Question What are the constructional parts of current transformer?
Answer Primary winding
Secondary winding
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

7. IMPORTANT QUESTIONS
Magnetic core.
Question Name the errors caused in current transformer.
Answer Ratio error
Phase angle error
Question Define ratio error.
Answer The ratio of energy component current and secondary current is known as
the ratio error.
Question How the phase angle error is created.
Answer It is mainly due to magnetizing component of excitation current
Question State the use of potential transformer.
Answer Used for m/s of high voltage
Used for energizing relays and protective circuits.
Question Name the errors caused in potential transformer.
Answer Ratio error
Phase angle error.
Question How the CT and PT are connected in the circuits.
Answer CT is connected in series and PT is connected in parallel.
Question Classify resistance
Answer Low resistance Medium resistance
High resistance
Question What is the range of medium resistance?
Answer Resistance of about 1 ohm to 100 kilo ohms is called medium resistance.
Question Name the methods used for low resistance measurement
Answer Ammeter – voltmeter method
Potentiometer method
Kelvin double bridge method
Ohm meter method.
Question Name the methods used for medium resistance measurement
Answer Ammeter – voltmeter method Substitution method Wheatstone bridge method
Carey foster bridge method
Question Where high resistance m/s is required?
Answer Insulation resistance of cables High resistance circuit elements
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

8. IMPORTANT QUESTIONS
Volume resistivity of a material Surface resistivity.
Question State the advantages of Wheatstone bridge method.
Answer Free from errors
The balance is quit independent of source emf
Question State the advantages of Kelvin double bridge method.
Answer Errors owing to contact resistance, resistance of leads can be eliminated by using
this Kelvin double bridge
Question What are the constructional features of doctor ohmmeter?
Answer Permanent magnet
Current coil
Pressure coil
Battery
Pointer with graduated scale.
Question Define megger.
Answer The megger is an instrument used for the measurement of high
resistance and insulation resistance
Question Name the parts of megger.
It consists of a hand driven dc generator and a direct reading true ohm meter.
Answer What is the range of low resistance?
Question Resistance of about 1 ohm and under are included in this class.
Answer What is the range of medium resistance?
Question Resistance of 100 kilo ohms and above is usually termed as high resistance.
Answer What ranges of resistance can be measured by using doctor ohmmeter.
Question 0 to 500 micro ohms
0 to 5 milli ohms
0 to 50 milli ohms
0 to 500 milli ohms
0 to 5 ohms.
Answer How resistance is measured in direct deflection method.
Question The deflection of galvanometer connected in series with the resistance to be
Measured gives a measure of the insulation resistance.
Answer Classify the cables according to their sheathing.
Question Armoured cables Unarmoured cables.
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

9. IMPORTANT QUESTIONS
Answer Name the leads present in megger
Question Earth lead
Line lead
Guard lead.
Answer How resistance is measured by using ohm meter method.
Question Series ohm meter method
Shunt ohm meter method.
Answer How resistance is measured in loss of charge method
Question In this method a capacitor is charged and discharged for a specific time period and
from this resistance is measured
Question State the balance equation used in bridge methods.
Answer The product of opposite branch resistances are equal
Question How the earth resistance is measured
Answer By using earth megger the value of surface earth resistance can be measured.
Question What are the basic elements of a generalized measurement system?
Answer The basic elements of a measurement system are primary sensing element,
variable conversion element, variable manipulation element, data transmission
element and data presentation element.
Question Define the term precision
Answer Precision is the measure of the consistency or repeatability of a series of
measurements.
Precision=1- Xi-X/Xi
Xi=the value of the i
th
measurements.
X=the average value of n measurements
Question What is the difference between accuracy and precision?
Answer Accuracy: It is the closeness with which an instrument reading approaches the
true value of the variable being measured.
Precision: It is the measure of reproducibility of the measurements.
Question List the different types of possible errors in measurements.
Answer The types of errors in measurements are systematic errors, Random errors and
gross errors
Question List any 4 static characteristics of a measuring system.
Answer The static characteristics of a measuring system are accuracy, sensitivity,
resolution, precision, drift and dead zone.
Question What are the different types of standards?
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

10. IMPORTANT QUESTIONS
Answer The different types of standards are international standards, primary standards,
secondary standards and working standards.
Question Define span.
Answer Span is defined as the algebraic difference the highest and lowest scale values of
an instrument.
Question What is random error?
Answer Random error is an error due to unknown causes and observed when the
magnitude and polarity of a measurement fluctuates in a unpredictable manner.
Question Define sensitivity of an instrument.
Answer Sensitivity of an instrument is a measure of the change in reading of an instrument
for a given change in the measured quantity.
Question Define resolution of an instrument.
Answer Resolution of an instrument is the smallest change in the measured quantity that
will produce a detectable change in the instrument reading.
Question Define limiting error
Answer In most instruments, the accuracy is guaranteed to be within a certain percentage
of full scale reading. Manufacturers have to specify the deviations from the
nominal value of a particular quantity. The limits of these deviations from the
specified value are defined a s limiting errors or guarantee errors.
Limiting error = accuracy x full-scale value.
Question Define calibration
Answer Calibration is the process of checking the accuracy of instruments by comparing
the instrument reading with a standard or against a similar meter of known
accuracy. It is also defined as marking the scale of an instrument.
Question Define fidelity
Answer Fidelity is defined as the degree to which a measurement system indicates
changes in the measured quantity without any dynamic error.
Question Define dynamic error
Answer Dynamic error is defined as the difference between the true value of the
quantity changing with time and the value indicated by the measurement
system if no static error is assumed. It is also called measurement error. It is
one the dynamic characteristics.
Question Define drift
Answer Drift is defined as slow variation of reading from a fixed value.
Question Define speed response
Answer Speed response is defined as the rapidity with which a measurement system
responds to changes in measured quantity. It is one of the dynamic
characteristics of a measurement system.
Question Define reproducibility
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

11. IMPORTANT QUESTIONS
Answer Reproducibility is defined as the degree of closeness with which
a given value may be repeatedly measured. It is specified in
terms of scale readings over a given period of time.
Question Define linearity
Answer The linearity is defined as the ability to reproduce the input characteristics
symmetrically and linearly
Question Define threshold
Answer Threshold is defined as the minimum value of the input at which the output starts
changing/increasing from zero.
Question Define resolution
Answer Resolution is defined as the smallest increment of quantity being measured which
can be detected with certainty being measured which can be detected with
certainty by an instrument.
Question Write the characteristics of the measurement system.
Answer Characteristics of measurement system is divided into two categories:
i. Static characteristics
ii. Dynamic characteristics
Question Write the main static characteristics?
Answer The main static characteristics are:
i. Accuracy
ii. Sensitivity
iii. Reproducibility
iv. Drift
v. Static error
vi. Dead zone
vii. Resolution
viii. Precision
ix. Repeatability
x. Stability
Question How controlling torque is produced?
Answer Using springs, & using control weight the controlling torque is produced
Question Why scale of gravity is non-uniform?
Answer The quantity is to measure is proportional to sin rather than in gravity control which is
not a uniform. Hence scale calibrated is not in uniform.
Question What are the different ways of producing damping torque in instruments?
Answer a) Air friction damping,
b) Fluid friction damping,
c) Eddy current damping.
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com

12. IMPORTANT QUESTIONS
Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical
& Electronics Engineering @ NRI Institute of Information Science &
Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053
Email:Jraysbhadoriya@gmail.com
From-
Mr. Jitendra Singh Bhadoriya
Assistant Professor
Department of Electrical & Electronics Engineering
NIIST, Bhopal