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Chapter: Measurements and Instrumentation - Comparison Methods of Measurements

Important Short Questions and Answers: Comparison Methods of Measurements

Measurements and Instrumentation - Comparison Methods of Measurements - Important Short Questions and Answers: Comparison Methods of Measurements

COMPARSION METHODS OF MEASUREMENT

 

1. What is the basic principle used in potentiometer?

 

Basic principle used in potentiometer is that the unknown emf is measured by comparing it with a standard known emf.

 

2.   Name the materials used in potentiometer.

 

The materials used in potentiometer are

i. German silver

ii. Manganin wire

 

3.   State the applications of potentiometer.

 

The applications of potentiometers are

i. measurement of unknown emf

ii. ammeter calibration

iii. Voltmeter calibration

iv. wattmeter calibration

 

4. State the advantages of crompton potentiometer.

 

The advantages of crompton potentiometer are:

i. More accuracy

ii. Easy to adjust

 

5.   What are the practical difficulties in A.C potentiometers?

The practical difficulties in A.C potentiometers are:

i.    More complicated

ii.   Accuracy is seriously affected

iii.  Difficulty is experienced in standardization.

 

6.   Classify AC potentiometers.

 

AC potentiometers are classified as

i. Polar potentiometer

ii.   Coordinate potentiometer.

 

7.   How the phase angle is measured in polar type potentiometers?

 

The phase angle is measured in polar type potentiometers from the position of phase

shifter.

 

8. List any two AC potentiometers.

 

The two AC potentiometers are i. Drysdale Tinsley potentiometer ii. Gall Tinsley potentiometer.

 

9.   State the advantages of AC potentiometers.

The advantages of ac potentiometers are

i.    They can be used for measurement of both magnitude and phase angle

ii.   They can be used for measurement of inductance of the coil.

iii.  They are used in measurement of errors in current transformers.

 

10. State the applications of AC potentiometers.

 

The applications of AC potentiometers are

i. Measurements of self inductance.

ii. Ammeter calibration

iii.  Voltmeter calibration

iv. Wattmeter calibration.

 

 

11. State the advantages of instrument transformers.

The advantages of instrument transformers are

i.    Used for extension of range

ii. Power loss is minimum

iii.  High voltage and currents can be measured.

 

12. State the disadvantage of instrument transformers.

 

The disadvantage of instrument transformers is that they cannot be used for DC measurements.

 

13. What are the constructional parts of current transformer?

The constructional parts of current transformer are

i.    Primary winding

ii.   Secondary winding

iii. Magnetic core.

 

14. Name the errors caused in current transformer.

The errors caused in current transformer are

i.    Ratio error

ii.   Phase angle error

 

15. Define ratio error

 

Ratio error is defined as the ratio of energy component current and secondary current.

 

16. How the phase angle error is created?

 

The phase angle is created mainly due to magnetizing component of excitation current.

 

17. State the use of potential transformer.

The use of potential transformer are

i.    They are used for measurement of high voltage

ii.   They are used for energizing relays and protective circuits.

 

18. How the current transformer and potential transformer are connected in a circuits?

 

In a current transfrmer is connected in series and potential transformer is connected in parallel

 

19. What is the range of medium resistance?

The range of resistance is about 1 ohm to 100 kilo ohms.

 

20. Name the methods used for low resistance measurement.

The methods used for low resistance measurement are

1.   Ammeter – voltmeter method

2.   Potentiometer method

3.   Kelvin double bridge method

4.   Ohm meter method.

 

21. What are the types of DC potentiometers?

The types of DC potentiometers are

i. Crompton’s Potentiometer

ii. Duo-Range Potentiometer

iii. Vernier Potentiometer

 

iv.  Brook’s Deflectional Potentiometer

 

22. What is a bridge circuit?

A bridge circuit consists of a network of four impedance arms forming a closed circuit. A source of current is applied to two opposite junctions. The current detector is connected to other two junctions.

 

 

23. What are the types of bridges?

The types of bridges are:

 

i.    DC bridge ii. AC bridge

 

 

24. What are the types of DC bridges?

The types of DC bridges are

i.    Wheatstone bridge

ii.   Kelvin Double bridge

 

 

25. What are the types of AC bridges?

The types of AC bridges are

i.    Capacitance comparison bridge

ii.   Inductance comparison bridge

iii. Schering bridge

iv.  Maxwell’s Inductance and capacitance bridge

v.   Hay’s bridge

vi.  Anderson bridge

vii. Wien bridge

 

26. Classify the cables according to their sheathing.

According to their sheathing cables are classified as

i.    Armoured cables

ii.   Unarmoured cables.

 

27. State the advantages of price’s guard wire method.

The advantage of price’s guard method is leakage current does not flow through the meter and therefore it gives accurate reading.

 

28. How the earth resistance is measured?

Earth resistance can be measured by using earth megger.

 

29. Which type of detector is used in ACbridges?

The detectors used in AC bridges are

i.    Vibration galvanometers

ii.   Tunable amplifier

iii.  Head phones

 

30. Name the sources of errors in AC bridge measurements.

The sources of errors in AC bridges are

i.    Errors   due   to   stray magnetic fields

ii. Leakage errors

iii.  Eddy current errors

iv.  Residual errors

v.   Frequency and waveform errors.

 

31. State the advantages of wein bridge.

The advantage of wien bridge is the balance equation is independent of frequency and therefore is more accurate.

 

32. State the disadvantage of wein bridge.

The disadvantage of wien bridge is a standard variable capacitor. Variable capacitor is more costly.

 

 

33. State the disadvantages of Hay’s bridge.

 

The disadvantages of Hay’s bridge is the balance equation is dependent of frequency and therefore any changes in frequency will affect the measurement.

 

34. State the use of Wein bridge.

 

Wien bridge is used for the measurement of unknown capacitance and frequency.

 

35. Define: Q-factor of the coil

 

Q-factor of the coil is defined as the ratio of power stored in the coil to the power dissipated in the coil.

 

36. Name the faults that occurs in cables.

Faults that occur in cables are

i.    Break down of cable insulation

ii.   Short circuit fault

iii.  Open conductor fault.

 

37. Name the loop test methods used in location of fault.

Loop test methods used in location of fault is

i.    Murray loop test

ii.   Varley loop test.

 

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