MCQ on Electrical Measuring Instruments with Answers

41. Chopper stabilized dc amplifier type electronic voltmeter overcomes the effect of

(a) Amplifier CMRR.
(b) Amplifier sensitivity.
(c) Amplifier drift.
(d) Electromagnetic interference.

42. True rms responding voltmeters use

(a) thermistors.
(b) RTDs.
(c) LVDTs.
(d) thermocouples.

43. Measuring and balancing thermocouples are used in a

(a) peak responding voltmeter.
(b) peak-to-peak responding voltmeter.
(c) average responding voltmeter.
(d) rms responding voltmeter.

44. An analogue electronic circuit that measures rms value of the input voltage by averaging the square of the instantaneous voltage level, responds slowly to the changes in the input signal due to

(a) the “square” function built into the circuit.
(b) the “square-root” function built into the circuit.
(c) the averaging function built into the circuit.
(d) none of the above.

45. In an electronic ohmmeter an op-amp is used as a

(a) summer.
(b) multiplier.
(c) buffer amplifier.
(d) integrator.

46. Electronic null detectors are

(a) less sensitive.
(b) more sensitive.
(c) more expensive.
(d) of excellent sensitivity, rugged construction and fairly expensive.

47. Which one of the following multirange voltmeters has high and constant input impedance ?

(a) PMMC voltmeter.
(b) Electronic voltmeter.
(c) Moving iron voltmeter.
(d) Dynamometer type voltmeter.

48. Which one of the following is basically a current sensitive instrument?

(a) PMMC instrument.
(b) CRO.
(c) Electrostatic instrument.
(d) FET input electronic voltmeter.

49. A voltage in the range of 0 – 10 mV with an output resistance of 1 MΩ can be measured by a meter of type

(a) thermal.
(b) moving iron.
(c) PMMC.
(d) electronic.

50. Which amplifier is used in an electronic multimeter ?

(a) Power amplifier.
(b) Buffer amplifier.
(c) Differential amplifier.
(d) Wideband amplifier.

51. Modern electronic multimeters measure resistance by

(a) using a bridge circuit.
(b) using an electronic bridge compensator for nulling.
(c) forcing a constant current and measuring the voltage across the unknown resistor.
(d) applying a constant voltage and measuring the current through the unknown resistor.

52. A multimeter is used for the measurement of the following :

1. Both ac and dc voltage.
2. Both ac and dc current.
3. Resistance.
4. Frequency.
5. Power.

Select the correct answer using the codes given
(a) 1, 2 and 4.
(b) 1, 2, and 5.
(c) 1, 3 and 5.
(d) 1, 2 and 3.

53. A symmetrical square wave voltage is read on an average response electronic voltmeter whose scale is calibrated in terms of rms value of a sinusoidal wave. The error in the reading is

(a) – 3.9%
(b) + 3.9%
(c) -11%
(d) + 11%

54. Consider the following statements:

1. Amplifier gain and phase shift.
2. Filter transfer functions.
3. Two port network parameters.
4. Power gain in a two port circuit.

Which of the above quantities can be measured using a vector voltmeter?
(a) 1 and 3 only.
(b) 1, 2 and 4.
(c) 1, 2 and 3.
(d) 3 and 4.

55. The Q-meter works on the principle of

(a) mutual inductance.
(b) self inductance.
(c) series resonance.
(d) parallel resonance.

56. Consider the following statements regarding the sources of error in a Q-meter.

1. If a coil with a resistance R is connected in the direct measurement mode and if the residual resistance of Q-meter is 0.1 R, then the measured Q of the coil would be 1.1 times the actual Q.
2. If the inductance to be measured is less than 0.1 µH, the error due to presence of residual inductance cannot be neglected.
3. The presence of distributed capacitance in a coil modifies the effective Q of the coil.

Of these statements
(a) 1, 2 and 3 are correct.
(b) 1 and 2 are correct.
(c) 2 and 3 are correct.
(d) 1 and 3 are correct.

57. In measurements made using a Q-meter, high impedance elements should preferably be connected in

(a) star.
(b) delta.
(c) series.
(d) parallel.

58. If the Q-factor of a coil is measured by varying the frequency, then

(a) the plot between Q and frequency is linear.
(b) the value of Q initially decreases with increase of frequency and afterwards it will increase with increase of frequency.
(c) the value of Q initially increases with increase of frequency and afterwards it will decrease with increase of frequency.
(d) the Q-factor remains constant irrespective of the frequency.

59. Oscilloscope is basically a

(a) voltmeter.
(b) ammeter.
(c) wattmeter.
(d) energy meter.

60. Beam of electrons in a cathode ray tube eminates because of

(a) secondary emission.
(b) thermionic emission.
(c) diffusion.
(d) post acceleration.