Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech III ELECTRONIC INSTRUMENTATION Previous Question Paper (May/June - 2019 - R15)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
What are the precautions that are to be taken to avoid errors while measuring sine wave.
Answer
To avoid errors when measuring sine waves, ensure the signal source impedance is low to prevent loading effects, maintain proper shielding to minimize electromagnetic interference (EMI), and ensure the measurement instrument has a high input impedance and sufficient bandwidth to accurately capture the waveform without distortion.
With necessary equations define envelope delay or group delay.
Answer
Envelope delay, or group delay, is defined as the rate of change of the phase shift with respect to frequency. It represents the time delay of the envelope of an amplitude-modulated signal passing through a system. It is mathematically expressed as:
where φ is the phase shift in radians and ω is the angular frequency in rad/s.
What are the reasons for employing DC amplifiers?
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What are choppers?
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Explain the purpose of synchronous detectors.
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Draw the block diagram of a simplified differential voltmeter.
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Define Mutual Inductance.
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Explain the purpose of megohmmeter.
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What are the problems encountered during measurement of impedance at radio frequencies.
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What are the disadvantages of transformer-ratio-arm bridges?
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Part B
Explain how Gain or Loss measurement can be done using Classical substitution method and Direct method. With neat diagrams explain how loop gain can be measured using elementary method. Also discuss the necessary changes needed for the circuit to measure loop gain under different conditions.
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Briefly discuss about the effects of low end cut-offs on square wave response. Explain about the method for measuring group delay.
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With a neat diagram explain about the input stage of a direct coupled amplifier using FET. Obtain the overall voltage gain of an improved differential amplifier with four integrated circuit blocks.
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With a neat diagram explain the basic circuit for automatically resetting the operating point of a direct coupled amplifier. Explain the purpose of a bilateral transistor chopper.
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With a neat block diagram explain the operation of servo DVM. Explain the operation of average responding detectors.
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What are sampling voltmeters? Explain their working with a neat block diagram. Write a short note on Alternating current probes.
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Discuss the frequency characteristics of Capacitors. With a neat diagram explain about the different Capacitance and Inductance meters.
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Discuss about the different meter methods to measure impedance. Explain the working of a Kelvin double bridge used to measure low valued resistances.
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Briefly discuss about the different types of low frequency bridges. Explain about the different measurements obtained from transmitting systems.
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Describe about the different methods for the measurement of precision resistance, precision capacitance and precision inductance. What is the purpose of a RF Vector Impedance meter? Explain.
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