# JNTU Previous Papers-B-Tech-EEE-3rd-Year-Instrumentation-Aug/Sep 2008

JNTU B.Tech Supplimentary Examinations, Aug/Sep 2008

INSTRUMENTATION

(Electrical & Electronic Engineering)

SET-III

1. (a) How the performance characteristics of an instrument are classified?

(b) Explain clearly the difference between Accuracy and Precision?

2. (a) Explain the spectra of a periodic rectangular pulse train for the following.

i) Amplitude

(ii) Phase spectra when time origin coincides with centre of pulse.

iii) Phase spectra with pulse starting at t=0.

(b) Define line spectra.

3. Draw and explain different parts of a CRT?

4. Explain with neat circuit diagram the working of the linear ramp type DVM.

5. (a) Explain the working of a heterodyne wave analyzer with a neat block diagram.

(b) Explain the principle and operation of basic spectrum analyzer with a neat block diagram.

6. Explain the factors that influence the selection of a transducer.

7. (a) Describe the following methods of temperature compensation for strain gauges

i. use of dummy gauge

ii. half bridge method.

(b) A single electrical resistance strain gauge of resistance 120 and having a gauge factor of 2 is bonded to steel having elastic limit stress of 400MN/m2. and modulus of elasticity 200GN/m2.Calculate the change in resistance due to

i. change in stress equal to 1/10th of the elastic range

ii. change of temperature of 20 0C if the material is advanced alloy. The resistance temperature coefficient of alloy is 20 × 10 – 6/ 0C.

iii. Calculate the strain due to the differential expansion of the guage metal and steel, if coefficient of linear expansion of the steel is 12 × 10 – 6/ 0C and that of the advanced alloy is 16 × 10 – 6/ 0C.

8. (a) Describe the principle and operation of Knudsen gauge with a neat sketch.

(b) Describe the operation of Ionization gauges for pressure measurement.