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Electrical Measurements & Measuring Instruments Multiple Choice Questions on “Potentiometric Integrating Type DVM”.
1. In a potentiometric DVM ________
a) voltage is compared
b) current is compared
c) resistance is compared
d) power is compared
Answer: a
Clarification: Potentiometric integrating type DVM employs voltage comparison. The unknown voltage is compared with a reference. The reference value is set by a calibrated potentiometer.
2. How to obtain balance?
a) by using a detector
b) by changing the pot setting
c) by supplying voltage
d) by using a transformer
Answer: b
Clarification: Balance is obtained in a potentiometric integrating type DVM by adjusting the settings of the potentiometer. The dial setting of the potentiometer gives the value of the unknown voltage.
3. In a potentiometric DVM, balance is obtained manually.
a) True
b) False
Answer: b
Clarification: Balance is obtained in a potentiometric integrating type DVM by adjusting the settings of the potentiometer. Hence in a potentiometric integrating type DVM, the balance is obtained automatically.
4. Unknown voltage is __________
a) converted to current
b) boosted
c) filtered
d) measured using a voltmeter
Answer: c
Clarification: In a potentiometric integrated type DVM, the unknown voltage is filtered. It is also attenuated to a suitable magnitude. This forms the input for the comparator. A chopper is usually used as an error detector.
5. How is the reference voltage obtained?
a) from a fixed current source
b) from a variable voltage source
c) from a variable current source
d) from a fixed voltage source
Answer: d
Clarification: Reference voltage is applied to the potentiometer. It is obtained from a source of fixed voltage. The position of the slider on the contact surface determines the value of the feedback voltage.
6. Feedback voltage is applied to the ________
a) comparator
b) error amplifier
c) potentiometer
d) sliding contact
Answer: a
Clarification: Comparator accepts the feedback voltage as an input. Comparator compares the values of the unknown voltage and the feedback voltage. Comparator then provides the difference between the feedback voltage and the unknown voltage as its output.
7. Output of the comparator is known as ________
a) amplified signal
b) error signal
c) feedback signal
d) attenuated signal
Answer: b
Clarification: Comparator then provides the difference between the feedback voltage and the unknown voltage as its output. This is also known as the error signal.
8. Slider movement depends on ________
a) current magnitude
b) resistance magnitude
c) voltage magnitude
d) power magnitude
Answer: c
Clarification: In a potentiometric integrating type DVM, the slider moves based on the magnitude of the feedback voltage with respect to the input voltage. Contact is pushed back to the place where the unknown voltage equals the feedback voltage.
9. Accuracy of a potentiometric DVM is ________
a) zero
b) medium
c) low
d) high
Answer: d
Clarification: In a potentiometric integrating type DVM, the accuracy is usually high. It generally depends on the reference of the digital to analog converter. Accuracy of the voltage to frequency converter is less important compared to that of the digital to analog converter.
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