JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III ELECTRONIC MEASUREMENTS AND INSTRUMENTATION Previous Question Paper (September - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
The pointer of d’ Arsonval meter movement gives full scale deflection of 20mA. The potential difference across the meter when carrying 20mA is 400mV. Determine i) the shunt resistance required to design 0- 200A range ammeter. ii) the series resistance required to design 0- 1000V range voltmeter.
Answer
Given: Full scale deflection current Im = 20 mA = 0.02 A, Voltage drop Vm = 400 mV = 0.4 V.
First, calculate the internal resistance of the meter Rm:
i) For an ammeter range I = 200 A, the shunt resistance Rsh is:
ii) For a voltmeter range V = 1000 V, the series multiplier resistance Rs is:
Explain the principle of working of True RMS responding voltmeter and outline its applications.
Answer
A True RMS responding voltmeter measures the effective heating value of an arbitrary waveform, regardless of its shape. Unlike average-responding meters calibrated for sine waves, it computes the root-mean-square value directly.
The working principle typically involves a thermal converter or an electronic circuit:
- The input signal is fed into a squaring circuit, which produces an output proportional to the square of the instantaneous input voltage (v2).
- This signal is passed through a low-pass filter or an integrator to obtain the average value of the squared input.
- A square-root circuit then processes this average to produce an output proportional to the square root of the mean, yielding the RMS value.
Applications include: Measuring non-sinusoidal waveforms such as square waves, triangular waves, and pulses; analyzing noise signals; and determining power dissipation in loads where harmonic content is significant.
Compare shunt ohmmeter and series ohmmeter.
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How can you extend the range of Voltmeter? Elaborate with example.
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Explain the principle of working of Function Generator with a neat sketch.
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Conclude the need of Heterodyne wave Analyzers.
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Conclude the need of Video signal generators.
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Explain the principle and working of Spectrum Analyzer with a neat sketch.
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Conclude the need of Time Base Circuits in CRO.
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Explain the principle of working of sampling Oscilloscope with a neat sketch.
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How can you measure frequency and phase using Lissajous figures? Elaborate.
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Compare Analog Storage and Digital storage CROs.
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Explain the working principle of Synchros and summarize its application.
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Explain the working principle of Gyroscope and summarize its application.
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How could you measure Velocity? Elaborate.
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Construct the bridge circuit to measure inductance and develop relation for unknown Inductance.
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