# Electrical Measurements Questions and Answers – Basic Electronic Voltmeter

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Basic Electronic Voltmeter”.

1. Low voltage signals can be measured by ___________
a) amplifiers
b) transformers
c) transducers
d) voltmeters

Explanation: Electronic voltmeters make use of amplifiers to measure low voltage signals. It consists of two or more stages of D.C. amplifiers.

2. Input impedance of an electronic voltmeter is ________
a) low
b) high
c) medium
d) zero

Explanation: In an electronic voltmeter, the input impedance is maintained very high. This is achieved by making use of an FET (Field Effect Transistor) at the input of an electronic voltmeter.

3. Meter can be isolated from the circuit in a basic D.C. electronic voltmeter.
a) True
b) False

Explanation: Field effect transistor (FET) acts as a source follower and provides very high input impedance. BJT along with resistors form a balanced bridge circuit. As a result the meter circuit can be isolated from the main circuit.

4. Bridge is balanced by ________
a) galvanometer
b) oscillator

Explanation: 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.

5. What is the effect of the input on the transistor Q2?
a) bias on Q2 decreases
b) bias on Q2 is constant
c) bias on Q2 is zero
d) bias on Q2 increases

Explanation: The bias on the transistor Q2 increases when the input voltage is applied. As a result a proportional amount of current flows through the meter. Hence the deflection of the meter is directly proportional to the applied voltage within the dynamic range.
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6. What is basic range of a meter?
a) causes maximum deflection
b) causes minimum deflection
c) causes zero deflection
d) causes medium deflection

Explanation: The input voltage that causes maximum deflection of the meter is known as the basic range of a meter. It occupies the lowest range on the range switch in the unamplified circuits.

7. High range can be obtained in a basic D.C. electronic voltmeter by ________
a) a transformer
b) an attenuator
c) a transducer
d) a resistor

Explanation: By making use of an attenuator in a basic D.C. electronic voltmeter, we get high range of values for the voltage reading. Attenuator is basically a voltage divider circuit with a predefined front panel.

8. Sensitivity of electronic voltmeter is high.
a) True
b) False

Explanation: In a PMMC voltmeter (Permanent Magnet Moving Coil), the sensitivity obtained is less and of the order of a few volts. In electronic voltmeters the sensitivity is very high and is of the order of at least 100 times as that compared to a PMMC voltmeter.

a) damages the meter
b) increases the temperature
c) doesn’t affect the meter
d) decreases the sensitivity

Explanation: As transistors saturate after a certain range of operating voltage and current, the value of the meter current is limited. As a result, overloading does not affect the meter and it remains safe.

Sanfoundry Global Education & Learning Series – Electrical Measurements.

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