Instrumentation Transducers

Measurement of Phase Angle

Question 1
Marks : +2 | -2
Pass Ratio : 100%
What is the relation for phase angle (in degree) of a signal with time delay Δt and frequency f?
3600∗f.∗ Δt
1800∗f∗ Δt
3600 ⁄ (f∗ Δt)
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.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Rejection capability of Phase sensitive detector is depended on the averaging time of smoothing filter.
True
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.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Phase difference between two voltages at frequencies above 10Hz can be measured using _________
CRO
Voltmeter
X-Y plotter
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.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
What is the operating range of X-Y plotter?
Below 5Hz
Above 10Hz
Above 1 KHz
Very high frequency
Explanation:
X-Y plotter is used for measuring the phase difference between signals with very low frequencies. That is below 5Hz.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
Which of the following relation is correct for phase angle and reactive power?
Reactive power = apparent power ∗ sin θ
Reactive power = apparent power ⁄ sin θ
Reactive power = Real power ∗ sin θ
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.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
What is the use of flip-flop in electronic phase meters?
To provide a delay
To provide stability
To save data for particular time duration
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.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which of the following is the expression of power factor?
cos θ
sin θ
tan θ
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.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Phase-Sensitive detectors are used for measuring phase of ______________
Sinusoidal signals only
Non periodic signals only
Periodic signals only
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.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
For what purpose, FET’s are included in phase sensitive detectors?
As SPDT switches, for working with very high frequency signals
As SPDT switches, for working with very low frequency signals
As SPST switches, for working with very high frequency signals
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.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
What is the expression for phase angle using X-Y plotter? (Assume t0 be time interval between zero crossing of signals and T
Explanation: