# Electronic Voltmeters MCQ || Electronic Voltmeter Questions and Answers

1. Low voltage signals in Electronic Voltmeter can be measured by ______

1. Amplifiers
2. Transformers
3. Transducers
4. Voltmeters

Explanation:

The electronic voltmeter uses amplification or rectification (or both) to measure either alternating- or direct-current voltages.

The amplifiers in the Electronic voltmeter not only supply power; for the operation but also make it possible for low-level signals, which produce a current less than 50 µA for full-scale deflection, to be detected which otherwise cannot be detected in the absence of amplifiers.

2. What will be the reading of the voltmeter in the given figure? 1. 100 V
2. 150 V
3. 0 V
4. 50 V

Explanation:

Ideally, the voltmeter has infinite resistance and the practical resistance of the voltmeter is very high.

So that no current or negligible current is flowing through the voltmeter.

The given circuit is open-circuited due to the very high resistance of the voltmeter and the current flowing through the circuit is zero.

Hence all the voltage drops appeared across the voltmeter.

∴ voltmeter reading is 150 volts.

3. Input impedance of an electronic voltmeter is ________

1. Low
2. High
3. Medium
4. Zero

Explanation:

An electronic voltmeter has very high input impedance and very low output impedance and the current drawn by the instrument for full-scale deflection is negligible. Hence, the instrument does not draw any significant current from the system whose voltage is being measured. This way the system does not get loaded at all thereby almost eliminating the loading effect.

4. A multimeter consists of

1. Current and Ohm meter
2. Voltmeter and Ohm meter
3. Voltmeter and Current meter
4. Voltmeter, current meter and Ohm meter

Answer.4. Voltmeter, current meter and Ohm meter

Explanation:

• A multimeter consists of a voltmeter, current meter, and Ohm meter
• Current drawn by an electronic circuit is in the order of mill amperes. We can measure this using multimeter
• The supply voltage to the DC motor is around 240 V, we can measure this voltage by using a multimeter
• We can do continue tests of motor winding by using a multimeter.

6. In DC Electronic Voltmeter ______ effectively isolates the meter circuit.

1. Amplifier
2. Attenuator
3. Electronic Switch
4. FET

Explanation:

DC Electronic Voltmeter consists of an input attenuator source follower and d.c. coupled amplifier. The purpose of the input attenuator is to provide input voltage levels that can be accepted by the d.c. amplifier. A FET is used to serve as a source follower at the input stage to obtain high input impedance. FET effectively isolates the meter circuit from the circuit under measurement. 7. Thermocouple meters are AC meters that respond to the ________ of a signal.

1. Peak value
2. Instantaneous value
3. Average value
4. RMS value

Explanation:

• Thermal-Thermoelectric uses the thermocouple for the measurement of the temperature, current, and voltage type of instrument known as the thermocouple instrument.
• It is used for both the AC and DC measurement. The thermocouple is an electric device that uses two wires of different metals.
• Thermocouple meters are AC meters that respond to the RMS value of a signal.

8. In DC Electronic Voltmeter bridge is balanced by _____

1. Galvanometer
2. Oscillator

Explanation:

The bridge circuit in a basic D.C. electronic voltmeter is balanced by making use of a zero adjustment resistor such that the pointer shows zero deflection. The bridge balance is obtained by a zero adjust resistor such that for zero input, the pointer shows zero. The bias on Q2 is such that i2 = i3 when the input is zero. Under such conditions, the potential of point an i.e. Va, and potential of point b i.e. Vb is the same. No current flows through the meter.

9. Which of the following features are associated with the rectifier instruments?

1. Small power loss
2. High degree of measuring accuracy
3. High sensitivity
4. All of the above

Explanation:

Rectifier type instruments are used for the measurement of AC voltages and currents by employing a rectifier element that converts AC to a unidirectional DC and then using a meter responsive to DC to indicate the value of rectified AC.

The indicating instrument is the PMMC instrument which uses a d’Arsonval movement.

Features of rectifier instruments:

• Liner scale
• High sensitivity
• A high degree of measuring the accuracy
• A small number of power losses

10. In DC Electronic Voltmeter what is the effect of the input voltage on the transistor Q2? 1. Bias on Q2 decreases
2. Bias on Q2 is constant
3. Bias on Q2 is zero
4. Bias on Q2 increases 