JNTU II B.Tech I Semester Regular Examinations, November 2008
CALIBRATION AND ELECTRONIC MEASUREMENTS
(Instrumentation & Control Engineering)
1. (a) What is the significance of measurements?
(b) Discuss the role of the following in a measurement system:
i. Primary sensing element
ii. Variable conversion element
iii. Data presentation element.
2. (a) Describe the unsaturated Weston cell as emf standard.
(b) What are the precautions taken while using them?
3. What are the various types of calibration? Explain.
4. (a) What is the disadvantage of d.c. amplifier used in electronic voltmeters? Explain how this disadvantage is overcome through the use of chopper stsbilized amplifiers.
(b) With the help of a neat circuit diagram, explain the operation of a chopper
amplifier type voltmeter using photodiodes.
5. Explain what is meant by sliding balance. How is this condition avoided by chosing
variables for manipulation of balance i.e. Why variables are so chosen that the equations balance are independent of each other.
6. Draw the block diagram of prescaled conventional frequency counter used for the
measurement of period. Explain the operation of each block? What are the various errors associated with a frequency counter and discuss each of them?
7. Draw the block diagram of a general purpose CRO and explain the functions of the following controlls.
(c) Horizontal and vertical positioning
8. (a) List the typical frequency responses of a strip chart recorder.
(b) List three functions that a recorder may simultaneously serve in industrial applications.