# GTU Electrical Measurements and Electronics Question Paper Dec 2010

GUJARAT TECHNOLOGICAL UNIVERSITY

B.E. Sem-Vth Examination December 2010

Subject code: 152402

Subject Name: Electrical Measurements & Electronics Instruments

Total Marks: 70

Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1 (a) Explain principle and operation of PMMC instrument. Derive torque equation for it.

(b) What are static and dynamic characteristics in measurement system? State various  static and dynamic characteristics of measuring instruments. Define any three static characteristics.

Q.2 (a) With neat diagram explain construction and operation of single phase energy meter. State various types of errors in potential transformer. Explain how they can be  reduced.

OR

(b) Explain measurement of three phase power using two watt meter method. Draw necessary diagrams.

Q.3 (a) Explain types of measurement method in broad sense. Classify and explain  measuring instruments.

(b) A PMMC instrument with 800 coil resistance gives Full Scale Deflection (FSD) with a 250A coil current. Calculate the required shunt resistance to convert the instruments into a DC ammeter with an FSD of 1) 40mA 2) 60mA.

OR

Q.3 (a) Explain (1) Q-factor of inductor (2) D-factor of capacitor.

(b) When the signal generator frequency of a Q meter is set to 1.45 MHz, the Q of a coil  is measured as 98 when C = 135pF. Determine the coil inductance and resistance.

Q.4 (a) Draw the circuit of a 4-bit DAC using R/2R network. Explain circuit operation and DAC output resolution.

(b) Explain Potentiometer calibration method.

OR

Q.4 (a) State various method of low resistance measurement. Explain any one method for  the same.

(b) List the different between power transformer and instrument transformer.

Q.5 (a) Give different accessories for measuring instruments. Explain 1) RF demodulator  probes

2) current probes.

(b) Explain voltage ohm meter (VOM) with neat diagram.

OR

Q.5 (a) Explain Creep, Overload Compensation and Temp Compensation in single phase  energy meter.

(b) Why light – beam Galvanometer is used? Explain its construction and operation.