Electronics and Communication Engineering - Measurements and Instrumentation

11. 

A moving coil instrument has a resistance of 0.6 Ω and full scale deflection at 0.1 A. To convert it into an ammeter of 0-15 A range, the resistance of shunt should be

A. 0.6 Ω
B. 0.06 Ω
C. 0.1 Ω
D. 0.004 Ω

Answer: Option D

Explanation:

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12. 

A piezoelectric force transducer has a charge sensitivity of 20 pC/N. It is connected to a charge amplifier and overall gain of transducer and amplifier is 50 mV/N. The gain of amplifier is

A. 1 mV/pC
B. 1.5 mV/pC
C. 2.5 mV/pC
D. 4 mV/pC

Answer: Option C

Explanation:

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13. 

An LVDT is used to measure displacement. The LVDT feeds a Voltmeter of 0-5 V range through a 250 gain amplifier. For a displacement 0.5 mm the output of LVDT is 2 mV. The sensitivity of instrument is

A. 0.1 V/mm
B. 0.5 V/mm
C. 1 V/mm
D. 5 V/mm

Answer: Option C

Explanation:

Final output = 2 x 10-3 x 250 = 0.5 V.

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14. 

Assertion (A): When a wattmeter is used for low impedance loads, the pressure coil is connected across the load.

Reason (R): A wattmeter measures apparent power.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

Answer: Option C

Explanation:

Wattmeter measures active power.


15. 

As per BIS there are 6 accuracy classes of instruments.

A. True
B. False

Answer: Option B

Explanation:

There are 8 classes of accuracy as per BIS.