Definition: The voltmeter which uses the amplifier for increases their sensitivity is known as the electronic voltmeter. It is used for measuring the voltages of both the AC and DC devices. The electronic voltmeter gives the accurate reading because of high input resistance.
The moving coil voltmeter is not able to detect the low voltages. The electronic voltmeter overcomes this problem. The electronic voltmeter has high input impedance because of which it detects the signals of very weak strength, hence gives the accurate reading. The high impedance means the circuit opposes the input supply.
The electronic voltmeter uses the transistor or vacuum tube. The transistor type voltmeter (TVM) has resistance because of which it cannot measure the current. And the vacuum voltmeter (VVM) has low resistance. Hence it is used for measuring the current.
Working of Electronic Voltmeter
The magnitude of the measurand voltage is directly proportional to the deflection of the pointer. The pointer is fixed on the calibrated scale. The point at which the pointer deflects indicates the magnitude of the input voltage.
In moving coil voltmeter the large power is drawn from the measurand circuit because of which the error occurs in their reading. This problem is overcome in the electronic voltmeter.
In electronic voltmeter, the pointer is deflected by taking the supply from the auxiliary amplifier circuit. The output voltages of the amplifier circuit are similar to the voltage of the test circuit. The extra power is not passing through the deflector because of which the meter gives the accurate reading.
Types of Electronic Voltmeter
The electronic voltmeter is categorized into two types. They are
- Analog Electronic Voltmeter
- Digital Electronic Voltmeter
Analog Electronic Voltmeter – The meter whose output is obtained by the deflection of the pointer on the calibrated scale is known as the analogue electronic measurement. It is a voltage measuring instrument which has high circuit impedance. The meter uses the electronic amplifier for controlling the input signals. The analogue electronic voltmeter is further classified into AC and DC analogue electronic voltmeter.
Digital Electronic Voltmeter – The voltmeter which gives the digital output reading of the measures voltage is known as the electronic voltmeter. The output of the digital electronic voltmeter is in the form of the numerical value. The digital electronic instruments reduce the human and the parallax error because the reading is directly shown in the numeric form.
Advantage of Electronic Voltmeter
The following are the advantages of the electronic voltmeter.
- Detection of Low-level signals – The electronic voltmeter uses the amplifier which avoids the load error. The amplifier detects the very small signals which produce the current of approximately 50μA. The detection of low-level signals is essential for determining the true value of the measurement.
- Low Power Consumption – The electronic voltmeter has vacuum tubes and the transistor which has the amplifying properties. It uses the auxiliary source for the deflection of the pointer. The measurand voltage controls the deflection of the sensing element. Thus, the circuit of the electronic voltmeter consumes very less power.
- High-Frequency Range – The working of the electronic voltmeter is free from frequency range because of the transistor. Along with the voltage, the signal of very high and low frequency can also be measured through it.
The electronics voltmeter measures the power only when they have the closed circuit, i.e., the current flows through their meter.