Anna University - Measurements and Instrumentation - Nov /Dec 2010 Question paper

Third Semester

Electrical and Electronics Engineering
(Regulation 2008)

Time : Three hours Maximum : 100 Marks
Answer ALL questions
PART A — (10 × 2 = 20 Marks)

1. Define static characteristics of an instrument.
2. What is meant by absolute error of measurement?
3. Why are the ordinary watt-meters not suitable for low power factor circuits?
4. What is a phase sequence indicator?
5. List the application of D.C. potentiometers.
6. What are parasitic voltages and how are they eliminated?
7. What is the purpose of a Post Deflection Acceleration (PDA) in a CRT?
8. Differentiate between LED and LCD.
9. What are the classifications of encoder?
10. What is the need of sample and hold circuit in A/D converter?

PART B — (5 × 16 = 80 Marks)

11. (a) (i) Draw the block diagram of functional elements of measuring system
and explain the function of each block. (Marks 8)
(ii) Explain the different types of errors in measurements. (Marks 8)
(b) (i) The probable values of two resistors and their S.D are specified as
R1 – 18.62 , S.D = 0.025 , R2 = 74.48 , S.D. = 0.05 . Find the
probable value and S.D for the two resistors when they are
connected in
(1) Series and
(2) Parallel. (Marks 8)
(ii) Discuss the different types of standards of measurements. (Marks 8)

12. (a) (i) What are the various types of digital voltmeters? With a neat
sketch explain the working principle of any one type of a digital
voltmeter. (Marks 8)
(ii) With a neat diagram explain the construction and its working
principle of elector dynamo-meter type watt-meter. Also derive its
torque equation. (Marks 8)
(b) (i) Explain the method of measurements of B.H curve of a ring
specimen with a neat diagram. (Marks 8)
(ii) Describe the construction and working principle of digital frequency
meter. (Marks 8)

13. (a) (i) Draw a neat sketch of a modern slide-wire D.C potentiometer and
discuss how the potentiometer is standardized. (Marks 8)
(ii) Describe how co-ordinate type potentiometer can be used for
calibration of a voltmeter and A.C energy meters. (Marks 8)
(b) (i) Explain the theory and working principle of Kelvin's double bridge
method for measurement of low resistance. Derive the relation for
finding unknown resistance. (Marks 8)
(ii) Discuss briefly how Hay's Bridge can be used for the measurement
of inductance. (Marks 8)

14. (a) (i) Explain the construction and its working principle of X-Y Recorder.
(ii) Briefly discuss the features of digital plotters and printers. (Marks 10)
(b) (i) Explain the working principle of electrostatic deflection system in a
CRT. (10)
(ii) Explain the working principle of digital storage oscilloscope. (Marks 6)

15. (a) (i) Explain the construction and working of unbounded and bonded
type strain gauges. (Marks 8)
(ii) Explain the construction and working of optical encoders with a
neat diagram. (Marks 8)
(b) (i) Draw the generalized block diagram of a digital data acquisition
system and explain. (Marks 8)
(ii) Explain the successive approximation method of A/D converter. (8)