Download Answer the following questions :-

Measuring Instruments
Chapter 3 : Voltmeters
Answer the following questions :Show True or False :1 - The loading-effect for VOM may cause error .
(
)
Choose the correct answer :1 ) When measuring voltage Vm = 45 V it is better to use
a ) VFS = 15 V scale.
b ) VFS = 50 V scale.
c ) VFS = 150 V scale.
d ) VFS = 500 V scale.
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Complete the following :1 – When measuring a voltage ( or current ) select a range that results in deflection
as close to …………………. as possible, this will minimize the effect of
…………………….. error.
2 - When measuring a voltage select a range so that ………………………………. .
This will minimize the effect of …………………….. error.
3- For a series connected multiplier resistors Voltmeter :
a – In the series arrangement of multiplier resistor, Diodes D1& D2 are normally
…………... biased and act as …………………….. .
b – When the current increases through the meter movement, D1 or D2 will
become ………………..……., thus …………………. Most of the current around the
meter movement.
c – Resistor RCAL is used to compensate for :
a) ……………………………………………
b) …………………………………………….
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Solve the following :
1 - Given a basic meter movement with IFS = 100 μA and Rm = 2 K Ω.
Use it to design a 0 to 10 v D.C. voltmeter include the following information:
a ) The sensitivity of the voltmeter ( S ).
b ) The input resistance of the voltmeter ( Rin ).
c ) The value of the series resistance ( Rs ).
d ) Sketch illustrating how the meter face can be calibrated to read voltage by
using the following table:
D%
Vin = D X IFS X Rin
100
80
60
40
20
0
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2 - Given a basic meter movement with IFS = 50 μA and Rm = 2 K Ω.
Use it to design an elementary multi-range series connected multiplier DC voltmeter
to measure the following ranges :
VFS = 0 ------ 0.1 V
= 0 ------ 50 V
= 0 ------ 100 V
a ) Design the elementary series circuit .
( Calculate the required Rs resistance values for each range )
b ) Draw the practical circuit for the meter movement.
Range
Rin = S VFS
Rs = Rin - Rm
0 ------ 0.1 V
0 ------ 50 V
0 ------ 100 V
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3 –A voltmeter on a 0 – 15 range ( with a meter movement full-scale 100 μA , 750 Ω
coil resistance ) is connected to measure the voltage across R2 .
( R1 = 47 K Ω , R2 = 82 K Ω ). Calculate :
R1=47 k
a) Thevenin equivalent circuit.
b) The original voltage ( Vo ).
c) The measured voltage ( Vm ) .
d) The percent of accuracy ( a % ) .
e) The percent of error ( e % )
15V
R1=82 k
15 V
R1=47
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4 – For the circuit shown in figure, a voltmeter with RIN = 60 K Ω is used to measure
the voltage between A and B, determine the following:
a) Thevenin equivalent circuit RTH &VTH
b) The original voltage ( Vo )between A and B.
c) The measured voltage ( Vm ) between A and B
d) The percent of accuracy ( a % ) .
18 K
e) The percent of error ( e % )
20 K
A
30 K
40 K
70 V
B
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5 - A meter movement has full scale 50 μA , 1700 Ω coil resistance is to be used as
a voltmeter. Design a series connected multiplier resistors multi range DC voltmeter
that provides the following ranges:
0 - 10 V
0 - 50 V
0 - 100 V
a )Draw the circuit .
b ) Calculate the required Rs resistance values for each range )
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