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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 3
46.
Consider the following statements
  1. Thermistor is more sensitive than platinum resistance thermometer
  2. The resistance of thermistor is solely a function of its absolute temperature whether the source of heat is external or internal
  3. Thermistor has linear temperature-resistance relationship
  4. Thermistor has linear negative temperature coefficient
Of the Statements, the correct statements are
1 and 2
3 and 4
1, 2, 3, 4
1, 2 and 4
Answer: Option
Explanation:

Thermistor is a non-linear device.

47.
A moving coil meter has 10 Ω resistance and requires 40 mA for full scale deflection. The shunt resistance required to convert it into 0-2 A ammeter is
0.1021 Ω
0.2041 Ω
0.256 Ω
0.4210 Ω
Answer: Option
Explanation:

.

48.
Which of the following instruments can be used for dc as well ac upto a few MHz?
  1. Moving iron instrument
  2. Thermocouple instrument
  3. Induction instrument
  4. Moving coil instrument
Select the correct answer as per following codes
2 only
2 and 3 only
1, 2 and 3 only
2 and 4 only
Answer: Option
Explanation:

Thermocouple instrument is based on heating effect and can be used for very high frequencies also.

49.

Assertion (A): Strain measurement using strain gauge invariably requires a dummy strain gauge.

Reason (R): The resistance of strain gauge depends on temperature.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true
Answer: Option
Explanation:

The dummy strain gauge compensates the error due to change in temperature because temperature affects both the active and dummy strain gauges equally.

50.
If a shunt of 200 Ω resistance is used with a galvanometer of 1000 Ω resistance, the multiplying power is
6
5
1/5
1/6
Answer: Option
Explanation:

If current through galvanometer is 1,

A current through shunt = . Total current = 6 I. Hence multiplying factor is 6.

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