Real Time Measurement and Instrumentation Interview Questions with Answers PDF
1. What is meant by measurement?Measurement is an act or the result of comparison between the quantity and a predefined standard.
2. Mention the basic requirements of measurement.
Basic requirements of measurement:-
i.The standard used for comparison purpose must be accurately defined and should be commonly accepted.
ii.The apparatus used and the method adopted must be provable.
3. What are the 2 methods for measurement?
Methods for measurement:-
* Direct method and
* Indirect method.
4. Explain the function of measurement system
Function of measurement system:-
The measurement system consists of a transducing element which converts the quantity to be measured in an analogous form. the analogous signal is then processed by some intermediate means and is then fed to the end device which presents the results of the measurement.
5. Define Instrument.
Instrument:-
Instrument is defined as a device for determining the value or magnitude of a quantity or variable.
Types of instruments:
There are 3 types of instruments
? Mechanical Instruments
? Electrical Instruments and
? Electronic Instruments.
7. Classify instruments based on their functions.
Functions of Instruments:
? Indicating instruments
? Integrating instruments
? Recording instruments
8. Give the applications of measurement systems.
Applications of measurement systems:
? The instruments and measurement systems are sued for
? Monitoring of processes and operations.
? Control of processes and operations.
? Experimental engineering analysis.
9. Why calibration of instrument is important?
Calibration of instrument:
Th calibration of all instruments is important since it affords the opportunity to check the instrument against a known standard and subsequently to errors in accuracy.
10. Explain the calibration procedure.
Calibration procedure:
Calibration procedure involves a comparison of the particular instrument with either.
? A primary standard
? A secondary standard with a higher accuracy than the instrument to be calibrated or An instrument of known accuracy.
11. Define Calibration.
Calibration:
It is the process by which comparing the instrument with a standard to correct the accuracy.
12. Name the different essential torques in indicating instruments.
? Deflecting torque
? Controlling torque
? Damping torque
13. Name the types of instruments used for making voltmeter and ammeter.
? PMMC type
? Moving iron type
? Dynamometer type
? Hot wire type
? Electrostatic type
? Induction type
14. State the advantages of PMMC instruments
Advantages of PMMC instruments:
? Uniform scale
? No hysterisis loss
? Very accurate
? High effuiciency
15. State the disadvantages of PMMC instruments
Disadvantages of PMMC instruments:
Cannot be used for ac m/s
Some errors are caused by temperature variations.
16. State the applications of PMMC instruments
Applications of PMMC instruments:
? m/s of dc voltage and current
? used in dc galvanometer.
17. How the range of instrument can be extended in PMMC instruments.
? In ammeter by connecting a shunt resister
? In voltmeter by connecting a series resister.
18. State the advantages of Dynamometer type instruments
Advantages of Dynamo meter:
? Can be used for both dc and ac m/s.
? Free from hysteresis and eddy current errors.
19. State the advantages of Moving iron type instruments
? Less expensive
? Can be used for both dc and ac
? Reasonably accurate
20. State the advantages of Hot wire type instruments
? Can be used for both dc and ac
? Unaffected by stray magnetic fields
? Readings are independent of frequency and waveform.
21. What are the constructional parts of dynamo-meter type watt meter?
? Fixed coil
? Moving Coil
? Current limiting resister
? Helical spring
? Spindle attached with pointer
? Graduated scale
22. Write down the deflecting torque equation in dynamo meter type watt meter.
Td á VI CosÖ
23. State the disadvantages of Dynamo meter type watt meter.
Disadvantages of Dynamo meter:
Readings may be affected by stray magnetic fields.
At low power factor it causes error.
24. Name the errors caused in Dynamo meter type watt meter.
Error due to pressure coil inductance
Error due to pressure coil capacitance
Error due to methods of connection
Error due to stray magnetic fields
Error due to eddy current.
25. How the errors caused by pc inductance is compensated.
By connecting a capacitor in parallel to the resister.
26. How the errors caused by methods of connection is compensated.
By using compensating coil.
27. Name the methods used for power measurement in three phase circuits.
? Single watt meter method
? Two watt meter method
? Three watt meter method.
28. What are the special features to be incorporated for LPF watt meter?
? Pressure coil circuit
? Compensation for Pressure coil current
? Compensation for Pressure coil inductance
29. Define Phantom loading.
Phantom loading:
Method by which energising the pressure coil circuit and current coil circuits separately is called phantom loading.
30. State the use of phantom loading.
Power loss is minimized.
31. Name the methods used in Watt meter calibration.
Watt meter calibration:
? By comparing with std wattmeter.
? By using voltmeter ammeter method.
? By using Potentiometer.
32. What are the types of energy meters?
Types of energy meters:
? Electrolytic meters
? Motor meters.
? Clock meters
33. Name the constructional parts of induction type energy meter.
? Current coil with series magnet
? Voltage coil with shunt magnet
? Al disc
? Braking magnet
? Registering mechanism
34. How voltage coil is connected in induction type energy meter.
It is connected in parallel to supply and load.
35. How current coil is connected in induction type energy meter.
It is connected in series to the load.
36. Why Al disc is used in induction type energy meter.
Why Al disc is used in induction type energy meter.
37. What is the purpose of registering mechanism.
It gives a valuable number proportional to the rotations.
38. What is the purpose of braking mechanism.
It provides necessary braking torque.
39. Define creeping.
Creeping: Slow but continuous rotation of disc when pc is energised and cc is not energised.
40. State the reason why holes are provided in Al disc.
State the reason why holes are provided in Al disc.
41. What is the basic principle used in potentiometer.
In potentiometer the unknown emf is measured by comparing it with a std known emf.
42. Name the potentiometer material used
potentiometer material used
? German silver
? Manganin wire
43. Define standardisation.
It is the process by which adjusting the current flows through the potentiometer coil to make the voltage across the std cell is equal.
44. State the applications of potentiometer.
Applications of Potentiometer:
? Used for m/s of unknown emf
? Used for ammeter calibration
? Used for Voltmeter calibration
? Used for wattmeter calibration
45. State the advantages of crompton potentiometer.
? More accurate
? Easy to adjust
46. What are the practical difficulties in ac potentiometers.
? More complicated
? Accuracy is seriously affected
? Difficulty is experienced in standardization
47. Classify ac potentiometers.
AC potentiometers:
? Polar potentiometer
? Coordinate potentiometer
48. How the phase angle is measured in polar type potentiometers.
It is measured from the position of phase shifter.
49. Name some ac potentiometers.
? Drysdale Tinsley potentiometer
? Gall Tinsley potentiometer
50. State the advantages of ac potentiometers.
Advantages of ac potentiometers:
? Can be used for m/s of both magnitude and phase angle
? Can be used for m/s of inductance of the coil.
? It is used in m/s of errors in CTS
Also Read=> Measurement and Instrumentation MCQs
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