JNTU III B.Tech Supplimentary Examinations, Aug/Sep 2008

JNTU III B.Tech Supplimentary Examinations, Aug/Sep 2008

INSTRUMENTATION

(Electrical & Electronic Engineering)

SET-II

1. Define the following

(a) Arithmetic mean

(b) Median

(c) Standard deviation

(d) Variance.

 

2. (a) Write about analog and digital signals with illustrations?

(b) Define all the standard test signals with suitable waveforms?

 

3. (a) Derive the relation for deflection sensitivity ‘Se’ of a CRT.

(b) With neat diagram explain the working function of analog storage oscilloscope.

 

4. List different types of DVM and explain any one of them with neat sketch?

 

5. (a) What is harmonic distortion? What are the types of the distortion? Discuss them.

(b) A capacitor of capacitance 245 ?F produces resonance at angular frequency of 5 × 106 rad/s, while a capacitor of capacitance 50 pF produces resonance with the second harmonic of this frequency. Calculate the inductance and the self capacitance of the coil.

 

6. (a) Explain the input and ouput characteristics of the transducers.

(b) Discuss the materials used for potentiometers.

 

7. (a) Define gauge sensitivity and derive expression for it.

(b) in order to measure strain in a cantilever beam a single strain gauge of resistance 1 K  and gauge factor 2 and temperature coefficient of 10 × 10 – 6/0C is mounted on one beam and connected in one arm of the bridge circuit. The other three arms of the bridge have resistances of 100  each. The bridge detector resistance is 100  and it’s sensitivity is 10mm/?A

i. Calculate deflector’s defletion for 0.1% strain

ii. Calculate the change in effective strain indicated when the room temperature increases by 10 0C.

(c) Mention few devices that are used for the measurement of Rotary displacement.

 

8. (a) Explain the principle of solid rod thermometer.

(b) The hot junction of a chromel- alumel thermocouple is connected to a potentiometer terminals is at 240C. The potentiometer whose terminals are at 24

0C reads 27.6mV. What is the temperature of the thermocouple junction. The calibration chart of the thermocouple is

Temp( 0C) 20 24 28 ……….. 480 488 493

Voltage(mV) 0.8 0.95 1.12 ……….. 26.25 26.72 26.04

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