JNTU
JNTU B.Tech II ELECTRICAL AND ELECTRONIC MEASUREMENTS Previous Question Paper (April/May - 2018 - R16)
Note: This question paper contains two parts A and B. 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 and may have a, b, c as sub questions.
PART A
How the instruments are classified?
Answer
Instruments are primarily classified into three categories: Absolute instruments (which give the value of the quantity in terms of their own constants), Indicating instruments (which display the instantaneous value of the quantity), and Recording instruments (which provide a continuous record of the quantity over time).
What are the essential features of indicating instruments?
Answer
The essential features of indicating instruments are: Deflecting torque to move the pointer, Controlling torque to bring the pointer to a rest position proportional to the quantity, and Damping torque to prevent oscillations and bring the pointer to a steady state quickly.
What are the merits of potentiometers?
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Compare the current and potential transformers.
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What are the merits and demerits of dynamo meter type watt meters?
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What are the essential characteristics of energy meters?
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What are the merits and demerits of Maxwell Bridge?
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How are resistances classified?
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What is the need of transducers?
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What are the used of capacitive transducers?
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PART B
Describe the construction details and working of a moving iron instrument.
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A moving coil milli-ammeter having a resistance of 10 ohms gives full scale deflection when a current of 5mA is passing through it. Explain how this instruments can be used for measurement of (i) current of 1 A and (ii) voltage up to 5V.
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Explain with the help of neat sketch the construction of a PMMC type moving coil ammeter. Give the equation for torque of the ammeter and the principle merits and demerits of these instruments. State the causes of change of accuracy with change in temperature and frequency.
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Explain the construction and working of a simple DC potentiometer.
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A 500/5A, current transformer, at its rated load of 25VA, has an iron loss of 0.2W and a magnetizing current of 1.5 A. It is supplying rated output to a meter having a ratio of resistance to reactance of 5. Calculate ratio error and phase angle.
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Explain the use of PT with the help of a connection diagram.
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The current is measured through a standard resistance of 0.1 ± 0.1% (standard deviation) by a potentiometer that is accurate to ± 0.0001V (standard deviation). The voltage across the resistance is measured to be 0.2514V. To what accuracy current has been determined.
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Discuss the various types of errors and their methods of compensation in the dynamometer type watt meter.
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In a particular measurement, the wattcmeters readings were 5kW and 1 kW. Calculate the power and power factor, if (i) both meters read direct and (ii) one of the meters has been reversed.
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Describe with the help of diagrams the construction and working of a domestic single phase energy meter.
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A meter, whose constant is 600 revaluations per kWh, makes 5 revolutions in 20 seconds. Calculate the load in kW.
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Explain the procedure of measuring a low resistance with the help of Kelvin’s double bridge. Derive the relation for finding unknown resistance.
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With the help of circuit diagram explain how capacitance can be measured by the use of Schering Bridge.
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Draw the general form of AC bridge and derive the general equation for its balance.
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Draw the circuit diagram of Anderson’s bridge. Explain its working. State its limitations.
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What are the merits and demerits of LVDT’s.
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Explain the piezoelectric transducers with necessary diagrams.
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Describe the capacitive transducers with diagrams.
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Discuss the measurement of temperature with thermistors with diagram.
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