Electronic Instruments MCQs - Electrical and Electronic Measurements

This Portion of Electrical andElectronic Measurements and Measuring instruments contains Electronic Instruments MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

This Section covers below lists of topics.

Electronic Voltmeters
Vacuum Tube Voltmeters(VTVMs)
Differential Amplifiers
Difference Amplifiers Type of Electronic Voltmeter
Source Follower Type of Electronic Voltmeter
D.C Voltmeter with direct Coupled Amplifier
Chopper Stabilized Amplifiers
Electronic Voltmeters using Rectifiers
True rms Reading voltmeters
Electronic Multimeters
Differential Voltmeter
Vector Voltmeter
Vector impedance meter
A.C Voltage measurements
Current Measurement using Electronic instruments
Measurement of Power at Audio Frequencies
Diode Sensor Based instruments
Measurement of power at radio Frequencies

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1. The resistances, R_DConnected in the bridge circuit of a difference amplifier type of electronic voltmeter are each 10kΩ. The value of R_Dis much smaller than the value of a.c drain resistance, r_d, of FETs. The trans-conductance of FETs is 0.005 mho. The value of current through the meter when an input voltage of 1V is applied to the gate of left FET with the gate of right hand FET grounded , and the meter resistance almost negligible is :

5 mA
2.5 mA
10 mA
1 mA.

2. In a source follower type electronic voltmeter, the trans-conductance of FETs is 0.005 mho and the resistance of the meter is 100Ω. The approximate value of current through the meter, when the input voltage is 1 V, is :

2.5 mA
5 mA
2 mA
1mA.

3. The power consumption of a d.c voltmeter using a direct coupled amplifier when measuring a voltage 0.5 V is of the order of :

A few watt
A few multiwatt
A few microwatt
A few nanowatt.

4. A chopper stabilized a.c amplifier may use :

An electro-mechanical chopper
Bipolar transistors as choppers
MOS field effect transistors as chopper
Light activated devices as chopper
All the above.

5. Electronic voltmeters which use rectifiers employ negative feedback. This is done

To increase the overall gain
To improve stability
To overcome nonlinearity of diodes
None of the above.

6. A voltage having symmetrical square waveshape is applied to an average reading voltmeter with scale calibrated in terms of rms value of a sinusoidal wave has an error of :

– 3.9%
+ 3.9%
– 11%
+ 11%

7. A true rms reading voltmeter uses two thermocouples in order

To increase sensitivity
That the second thermocouple cancels out the no-linear effects of the first thermocouple
To prevent drift in the d.c amplifier
All the above.

8. In an electronic ohmmeter, an OP-AMP is used as a :

Summer
Multiplier
Buffer amplifier
Integrator

9. A voltmeter with a broad band width has :

Low noise level and high Sensitivity
High noise level and high sensitivity
High noise level and low sensitivity
Low noise level and low sensitivity.

10. In a circuit of RF voltmeters

Vacuum tube diodes are used
Conventional PN junction diodes are used
Schottky barrier or point contact type diodes are used
All the above.

11. An electronic voltmeter is more reliable as compared to multimeter for measuring voltages across low impedance because

its sensitivity is high
it offers high input impedance
it does not alter the measured voltage
its sensitivity and input impedance are high and do not alter the measured value

12. VTVM can be used to measure

dc voltage
ac voltage of high frequency
dc voltage and ac voltage up to the order of 5 MHz frequency
ac voltage of low frequency

13. Transistor voltmeter

cannot measure ac voltage
cannot measure high frequency voltage
cannot be designed to measure resistance as well as voltage
can measure ac voltage

14. An electronic voltmeter provides more accurate readings in high-resistance circuits as compared to a nonelectronic voltmeter because of its

low meter resistance
high Ω/V ratings
high V/Ω ratings
high resolution

15. The input impedance of a TVM as compared to that of a VTVM is

low
high
same
not comparable

16. The power consumption of a dc voltmeter using a direct coupled amplifier when measuring a voltage of 0.5 volt and having an input impedance of 10 MΩ is

a few nanowatts
a few milliwatts
a few microwatts
a few watts

17. FETs are used in the amplifier to get

high output impedance
high input impedance
low output impedance
low input impedance

18. A direct voltage is applied to a peak diode voltmeter whose scale is calibrated to read rms voltage of a sine wave. If the meter reading is 36 Vrms, the value of the applied direct voltage is

51 volts
25 volts
36 volts
71 volts

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

Both ac and dc voltage

Both ac and dc current

Resistance

Frequency

Power

Select the correct answer using the codes given:

1, 2 and 4
1, 2 and 5
1, 3 and 5
1, 2 and 3

20. Modern electronic multimeters measure resistance by

using an electronic bridge compensator for nulling
forcing a constant current and measuring the voltage across the unknown resistor
using a bridge circuit
applying a constant voltage and measuring the current through the unknown resistor

21. An n-bit A/D converter is required to convert an analog input in the range of 0–5 volt to an accuracy of 10 mV. The value of n should be

22. Which of the following is not true for a digital frequency counter?

less costly
high accuracy
accepts inputs in the form of train of pulses
wide range of frequency measurement

23. The resolution of a 12-bit analog to digital converter in per cent is

0.04882
0.09760
0.01220
0.02441

24. A DVM measures

peak value
rms value
average value
peak to peak value

25. Which of the following measurements can be made with the help of a frequency counter?

Fundamental frequency of input signal

Frequency components of the input signal at least up to third harmonics

Time interval between two pulses

Pulse width

Select the correct answer using the codes given below:

2 and 4
1 and 2
1, 2 and 3
1, 3 and 4

26. Accuracy of DVM is specified as

percentage of the full scale reading
percentage of the actual reading
number of least significant digit
all of these

27. A PMMC meter has an internal resistance 200Ω and the current required for its full scale deflection is 50µA. the metering is capable of measuring, on its own, a maximum voltage of :

5 mV
10 mV
5 µV
10 µV

28. A PMMC meter has an internal resistance 500Ω and the current required for its full scale deflection is 100µA.the power consumed by the meter is :

5 µW
5 mW
5 W
0.5 µW.

29. An average reading VTVM uses one diode connected in series with an external resistance. A high value of series resistance is used so that the instrument should have :

A high input impedance
A linear v – i characteristics
Low power consumption
All the above.

30. In a compensated shunt type peak reading VTVM a bucking battery with a series adjustable resistance is used for :

Providing power of the circuit
Zero setting
The purpose of amplifying low level signals
All the above.

31. In a different amplifier using two FETs, a resistance has to be reducing the meter current to zero even when no voltage is applied to the circuit. This is necessitated on account of :

Mismatch between characteristics of the FETs
Difference between tolerances values of resistors used in the circuit even though they are marked nominally equal.
Variations in the operating voltage of the circuit.
Both (a) and (b).

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Electrical and Electronic Measurements – Electronic Instruments MCQs