# Instrumentation Transducers Questions and Answers – Measurement of Phase Angle

This set of Instrumentation Transducers Multiple Choice Questions & Answers (MCQs) focuses on ” Measurement of Phase Angle”.

1. Phase difference between two voltages at frequencies above 10Hz can be measured using _________
a) CRO
b) Voltmeter
c) X-Y plotter
d) Multi meter

Explanation: For signals with frequencies greater than 10Hz, phase angle can be measured using CRO. Two signals are applied on two channels and the phase difference is measured from the screen.

2. What is the operating range of X-Y plotter?
a) Below 5Hz
b) Above 10Hz
c) Above 1 KHz
d) Very high frequency

Explanation: X-Y plotter is used for measuring the phase difference between signals with very low frequencies. That is below 5Hz.

3. What is the expression for phase angle using X-Y plotter? (Assume t0 be time interval between zero crossing of signals and T be time period of signals).
a) (360T0) ⁄ t0
b) (180 T0) ⁄ t0
c) (360 t0) ⁄ T0
d) (180 t0) ⁄ T0

Explanation: t0 is the time interval between zero crossing of two signals of the same frequency, and T0 is the time period of signals. Phase angle is represented by φ and is expressed in degree.

4. What is the use of flip-flop in electronic phase meters?
a) To provide a delay
b) To provide stability
c) To save data for particular time duration
d) To produce rectangular pulse

Explanation: Flip-flop in electronic phase meters are used to produce a rectangular pulse with duration t which is equal to phase difference between signals.

5. Phase-Sensitive detectors are used for measuring phase of ______________
a) Sinusoidal signals only
b) Non periodic signals only
c) Periodic signals only
d) Both periodic and non-periodic signals

Explanation: Phase sensitive detectors are used to measure the phase and amplitude of periodic signals. It is done by comparing a signal with a standard reference signal.
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6. Rejection capability of Phase sensitive detector is depended on the averaging time of smoothing filter.
a) True
b) False

Explanation: Rejection of noise signals in p.s.d is depended on the averaging time of smoothing filter. Higher the averaging time, greater is its rejection capability.

7. For what purpose, FET’s are included in phase sensitive detectors?
a) As SPDT switches, for working with very high frequency signals
b) As SPDT switches, for working with very low frequency signals
c) As SPST switches, for working with very high frequency signals
d) As SPST switches, for working with very low frequency signals

Explanation: Field effect transistors are included as single-pole, double-throw switches to work with very low frequency signals.

8. Which of the following relation is correct for phase angle and reactive power?
a) Reactive power = apparent power ∗ sin θ
b) Reactive power = apparent power ⁄ sin θ
c) Reactive power = Real power ∗ sin θ
d) Reactive power = Real power ⁄ sin θ

Explanation: From the power triangle, using relation for sin function we obtain Reactive power is the product of apparent power and sin of phase angle.

9. Which of the following is the expression of power factor?
a) cos θ
b) sin θ
c) tan θ
d) sec θ

Explanation: Power factor is a measure of power usage of a system from total supplied power. It can be expressed as cos θ, in which θ represents phase angle.

10. What is the relation for phase angle (in degree) of a signal with time delay Δt and frequency f?
a) 3600∗f.∗ Δt
b) 1800∗f∗ Δt
c) 3600 ⁄ (f∗ Δt)
d) 1800 ⁄ (f∗ Δt)

Explanation: Phase angle of a signal in degree can be measured using the above formula, if frequency and time delay are known.

Sanfoundry Global Education & Learning Series – Instrumentation Transducers.

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