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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 2
26.
In figure, the position of voltmeter and ammeter are exchanged. It may result in damage to
both the instruments
ammeter
voltmeter
neither of two
Answer: Option
Explanation:

Very high current will flow through ammeter because ammeter resistance is very low.

27.
The volt ratio box is basically a
potential divider
current transformer
a high resistance voltmeter
either (a) or (c)
Answer: Option
Explanation:

DC potentiometer can measure voltages upto about 1.5 V. Volt ratio box is used to reduce the unknown voltage so that it can be measured by dc potentiometer.

28.
A sinusoidal ac voltage of amplitude 100 V is applied to a rectifying device which offers 10 Ω resistance in forward direction and infinite resistance in backward direction. A moving coil ammeter is also connected in the circuit. The reading of ammeter will be
10 A
5 A
3.185 A
14.14 A
Answer: Option
Explanation:

Moving coil instrument indicates average value

.

29.
A variable reluctance tachometer has 180 teeth on rotor. The speed of shaft on which it is mounted in 1200 rpm. The frequency of output pulses is
1800 per second
3600 per second
4800 per second
5600 per second
Answer: Option
Explanation:

.

30.
In the wheatstone bridge in figure, each resistance is increased by 0.05%. The value of v0 will be
50 mV
5 mV
0.1 mV
zero
Answer: Option
Explanation:

Output of first op-amp is -2V, -V2.

Therefore, .

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