JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II TRANSDUCERS AND INSTRUMENTATION Previous Question Paper (November/December - 2020 - R13)
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How can you measure displacement using potentiometers? Explain.
Answer
A potentiometer measures displacement by converting linear or angular mechanical movement into a proportional change in electrical resistance. It consists of a resistive element (such as a wire-wound coil or conductive plastic) and a movable wiper contact.
When the object whose displacement is to be measured is attached to the wiper, the movement of the object causes the wiper to slide along the resistive element. This action changes the length of the resistive path between the wiper and one of the terminals. According to the principle of a voltage divider, the output voltage across the wiper and one end of the potentiometer varies linearly with the position of the wiper.
The output voltage is given by the formula:
where Vin is the excitation voltage, x is the displacement of the wiper, and L is the total length of the resistive element. By measuring the change in output voltage, the displacement can be accurately determined. These devices are widely used for their simplicity, low cost, and high output levels, though they are subject to mechanical wear and friction.
A resistance strain gauge with a gauge factor of 2 is connected to a steel member, which is subjected to a strain of 1 × 106. If the original resistance of the gauge is 150 ohms, calculate the change in the resistance.
Answer
Given parameters:
Gauge factor (G) = 2
Strain (ε) = 1 × 10-6
Original resistance (R) = 150 Ω
The relationship between the change in resistance and strain is defined by the gauge factor formula:
Rearranging to solve for the change in resistance (ΔR):
Substituting the given values:
The change in resistance is 0.0003 Ω.
Explain the working principle of LVDT.
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How the gyroscope velocity sensor works? Explain.
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Explain about Variable reluctance pick up.
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How can you measure torque on rotating shafts? Explain.
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How do you measure force using Piezo-electric transducer? Explain.
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State the merits and demerits of bonded strain gauges.
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How to extend the range of a ammeter? Explain.
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Obtain the balance condition for Wheatstone bridge.
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Calculate the value of the multiplier resistance in the 10V range DC voltmeter, which uses a 100 µA meter movement with an internal resistance of 100 ohms.
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Explain with a diagram the working of Maxwell’s bridge.
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Explain the average time period mode of operation of electronic counter.
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Write short notes on wave analyzers.
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Explain about cable transmission of analog voltage and current signals.
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How the Synchro position repeater system works? Explain.
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