Exercise: Measurements And Instrumentation

Questions for: Measurements And Instrumentation

A single element strain gauge bridge has two fixed resistances R1 and R1 of 120 Ω each and a variable resistance which gives full deflection at 120 Ω for zero strain and 120.6 Ω for straine e. If gauge factor is 2, strain e is
A:
0.0025
B:
0.0035
C:
0.005
D:
0.0075
Answer: A

.

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A moving iron voltmeter reads 250 V when connected to 250 V dc. If connected to 250 V 50 Hz, the voltmeter reading is likely to be
A:
250 V
B:
252 V
C:
248 V
D:
210 V
Answer: C

The inductance of coil will allow slightly less ac current. Hence reading slightly less.

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If an inductance L is connected in one arm of bridge and resistance R1, R2, R3 in other three arms
A:
the bridge cannot be balanced
B:
the bridge can be balanced
C:
the bridge is balanced for some specified value of frequency
D:
the bridge is balanced for some specific values of R1, R2, R3
Answer: A

To balance the bridge both magnitudes and phase angles of voltages have to be balanced.

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An accelerometer has a seismic mass of 0.05 kg and spring constant of 3 x 105 N/m. If maximum displacement of mass is ± 1 mm, the maximum acceleration which can be measured is
A:
30 m/s2
B:
60 m/s2
C:
90 m/s2
D:
120 m/s2
Answer: B

0.05 x a = 3 x 103 x 10-3 or a = 60 m/s2.

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Electrostatic voltmeter is suitable only for low voltages.
A:
True
B:
False
C:
D:
Answer: B

It is suitable for high voltage.

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