JNTU
JNTU B.Tech II ELECTRICAL AND ELECTRONIC MEASUREMENTS Previous Question Paper (February - 2024 - R16)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
(25 Marks)
What are the types of instruments based on the form of measurement?
Answer
Based on the form of measurement, instruments are classified into two types:
- Absolute Instruments: These provide the value of the quantity to be measured in terms of the physical constants of the instrument and its own deflection. No prior calibration is required (e.g., Tangent Galvanometer).
- Secondary Instruments: These are calibrated by comparison with an absolute instrument or another previously calibrated secondary instrument. The value of the electrical quantity is directly indicated by the deflection of the instrument (e.g., Ammeters, Voltmeters, and Wattmeters).
What are the merits of spring control devices?
Answer
The merits of spring control devices in electrical measuring instruments include the following:
- High sensitivity: Spring control provides a restoring torque that is directly proportional to the angle of deflection, allowing the instrument to respond accurately to small changes in the measured quantity.
- Versatility in mounting: Unlike gravity control, which requires the instrument to be placed in a strictly vertical position, spring-controlled instruments can be used in any position, making them suitable for portable equipment.
- Compact design: The mechanism is lightweight and occupies minimal space within the instrument casing, contributing to a smaller overall size and lower manufacturing costs.
What are the effect of phase angle error AN Instrument Transformers?
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Write the operating procedure of D.C. Crompton’s potentiometer.
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What is creeping? How can it be prevented?
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What are the main difference between LPF and UPF wattmeter’s?
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What are the various methods that can be employed for the measurement of low resistance?
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What are the merits of Anderson’s bridge?
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What is transducer? Give applications.
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What are the advantages of electrical transducers?
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Part B
(50 Marks)
Explain various methods of providing damping torque in an indicating instrument.
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The coil of a measuring instrument has a resistance of 1 Ω and the instrument reads upto 250 V when a resistance of 4.999 Ω is connected in series. Find the current range of the instrument when used as an ammeter with the coil connected across a shunt of resistance (1/499) Ω and the exact value of series resistance to be connected to measure 500 V DC.
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Explain the principle and working of an M.I. instrument.
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Describe principle of electrostatic instrument with a neat sketch.
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Describe how Drysdale- Tinsely AC Potentiometer is standardized.
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In the measurement of power by a polar potentiometer, the following readings were obtained: Voltage across a 0.2 ohms standard resistance in series with the load = 1.46 320 V, voltage across a 200:1 potential divider across the line = 1.37 560 V. Estimate the current, voltage, power and power factor of the load.
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Explain difference between AC and DC potentiometers.
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At its rated load, 25 VA, a 100/5 ampere current transformer has an iron loss of 0.2 W and a magnetizing current of 1.5 A. Calculate its error and phase angle when supplying rated output to a meter having a ratio resistances to reactance as 6.0.
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Explain the features of low power factor wattmeter.
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Two wattmeter’s used to measure the power input in a 3-phase circuit indicate 1000 W and 5000 W respectively. Find p.f of the circuit. (i) When both wattmeter readings are positive and (ii) When the latter is obtained by reversing the current coil connections.
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Derive the torque equation of single phase induction type energy meter.
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Explain the testing by phantom loading using R.S.S. meter.
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Explain how the Kelvin bridge overcomes the limitations of the Wheatstone bridge. Why do you call it a double bridge?
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Each of the ratio arms of a laboratory type Wheatstone bridge has guaranteed accuracy of ± 0.05 %, while the standard arm has a guaranteed accuracy of ± 0.1 %. The ratio arms are both set at 1000 Ω and bridge is balanced with standard arm adjusted to 3154 Ω. Determine the upper and lower limits of the unknown resistance, based upon the guaranteed accuracies of the unknown bridge arms.
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What is the Maxwell’s inductance bridge? Derive its balance equation.
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In a Schering bridge, the component values with usual notations are, R1 = 10 kΩ; C1 = 0.1 μF; R2 = 12 kΩ; C3 = 0.2 μF at balance. Determine the value of CX and RX if the AC input given has a frequency of 150 Hz.
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Explain the electrical transducers and selecting a transducer.
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Explain working principle of LVDT and state advantages and disadvantages of LVDT.
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Explain construction of thermistor. Give its characteristics and explain the different applications of thermistor.
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Suggest and explain a suitable instrumentation system to measure the level in petrol tank.
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