Chapter - 1
Questions
Measuring Instruments
Chapter 1 : Analog Meter Movements
Answer the following questions :Show True or False :1- The effective error Em is related to the measured current Im and the calibration
error as Em % = ( CE / Im ) x 100 % .
2- The taut-band movement more sensitive than the D'arsonval meter movement.
3- The 100 % accuracy means that the measured value is exactly equal to
the true value .
4- When the Rm of the meter is relatively high this means that the accuracy is very
high.
5- The Dynamometer has higher sensitivity than the D'arsonval meter movement.
6- The internal resistance of the ideal meter movement is high.
7 – The loading effect for a measuring instrument may cause an error .
8 - The iron - vane movement primarily used for low frequencies AC measurements.
9 – The sensitivity of meter movement means the smallest possible change in
current would produce a readable change in pointer deflection.
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Switching Section
Chapter - 1
Questions
Solve the following :
1 ) For the circuit in figure IFS = 500 µA and Rm = 400 Ω
following :
a ) The original current Io
b ) The measured current Im
c ) % of accuracy a
d ) % of error e
. determine the
2 ) The accuracy of a 0 to 100 µA meter movement is stated as 4 percent
of the full scale value
1. The amount of calibration error ( CE ) .
2. The range ( R ) of current when the meter reads 60 µA .
3. The percentage error ( Effective error Em % ) at the measured current.
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Switching Section
Chapter - 1
Questions
Questions :
1 ) a - Complete the main parts on the figure of the D'arsonval meter movement .
b ) From the above figure (D'arsonval meter movement )complete the following :
1 ) The purpose of the horseshoe magnet is to
.................................................................. ..................................................................
.......................................................................................................................................
2 ) The purpose of the spring is to
.................................................................. ..................................................................
.......................................................................................................................................
3 ) The purpose of the moving coil is to
.................................................................. ..................................................................
.......................................................................................................................................
4 ) The purpose of the Jeweled Bearing is to
.................................................................. ..................................................................
.......................................................................................................................................
5 ) The purpose of the Aluminum Frame is
.................................................................. ..................................................................
.......................................................................................................................................
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Switching Section
Chapter - 1
Questions
Choose the correct answer :1 ) The taut-band movement is used to measure .
a ) The average value of the current .
b ) The RMS value of the current .
c ) The volts .
2 ) The accuracy of the meter defined as :
a ) a = Im / Io
b ) a = R / R+ Rm
c ) all the above
3 ) The error in measuring the current is :
a ) e = 1/ 2 Im
b)e = 1-a
c ) e = I o - ( Im / Io )
4 ) The accuracy is stated as :
a ) The measured value ( Im )
b ) The calibration error ( CE )
c ) A percentage ( % age ) of Full Scale Deflection.
5 ) The range of the measured current that will be indicated is :
a ) Im x CE
b ) Im + CE
c ) The actual measured value
6 ) The scale of the Dynamometers is :
a ) linear scale .
b ) log scale .
c ) non-linear
7 ) The scale of the taut-band movement is :
a ) linear scale .
b ) log scale .
c ) non-linear
8 ) The scale of the D'Arsonval meter movement is :
a ) linear scale .
b ) log scale .
c ) non-linear
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Switching Section
Chapter - 1
Questions
9 ) The scale of the iron - vane movement is :
a ) linear scale .
b ) log scale .
c ) non-linear
10 ) All common meter movement are based on the law of magnetism, which states
that
a) Like magnetic poles attract.
b) Opposite magnetic poles repel.
c) Like magnetic poles repel.
d) Electromagnetic poles repel.
11 ) The basic meter movement measure:
a ) Current.
b ) Power.
c) Voltage.
d) resistance.
12 ) The D'Arsonval movement uses
a) Two vanes.
b) A moving coil and a fixed permanent magnet.
c) Three coils.
d) A fixed coil and a moving permanent magnet.
13 ) The iron – vane meter movement is constructed with
a) Three coils, two fixed and one moving coil.
b) Two vanes (one fixed and one moving) and a single fixed coil.
c) A moving coil and a fixed permanent magnet.
d) A fixed coil and a moving permanent magnet.
14 ) When measuring current Im = 30 µA by a with IFS = 100 µA with 3 % accuracy,
we can say that the meter within range if the measured value equal:
a) 27 µA.
b) 32 µA.
c) 30 µA.
d) all of the above.
a)
b)
c)
d)
15 ) The meter movement accuracy is usually specified as:
Friction.
A percentage of measured value.
Linearity.
A percentage of full scale.
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Switching Section
Chapter - 1
Questions
Answer the following questions :Complete the following :very low - effective error - 100 % accuracy - taut-band - ( 1 - a ) - Iron vane
- Dynamometers - Non Linear - sensitivity . Concentric vane - radial vane Linear
1- The ...........……................ movement is basically used for low frequency AC
measurement .
2- The internal resistance of the ideal meter movement is ..........................................
3- The D'arsonval meter movement has higher sensitivity than the ............................
4- The ................................................... means that the measured value is exactly
equal to the true value .
5- The error in measuring the current is equal to .................................
6 - The .......….................... movement is used to measure the average value of the
current .
7 - The ........................... Em in current measurements is equal to ( CE / Im ) x 1.
8 – The D’Arsonval meter movement has a …………………… sacle.
9 – The concentric – vane meter movement has a ……………………… scale.
10 – The …………………… of meter movement means that the smallest possible
change in current would produce a readable change in pointer deflection.
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Switching Section