The AC voltmeters are of various types depending on the type of voltage is measures. The PMMC meter then moves the pointer according to the value of the RMS value of AC. The amplified signal obtained from the multistage amplifier is then passed to PMMC meter. The DC voltage obtained from the rectifier is passed through the multistage amplifier. The AC voltage is converted into DC voltage with the help of rectifier. The voltage measured is given as input to the AC voltmeter circuit. The AC voltage to be voltmeter comprises an attenuator, rectifier, multistage amplifier and a PMMC meter. The Chopper type DC voltmeter provides high sensitivity as compared to direct coupled DC voltmeter. Then amplified AC signal is then again passed through Chopper demodulator and then through a low pass filter, it gets introduced in a PMMC meter for measuring peak value of DC voltage. In case of high current, the FET prevents the excess current to flow from measuring meter so that it does not burn out.Ĭhopper Type DC voltmeter uses a chopper modulator to convert the DC voltage into AC voltage and then pass it through AC amplifier. The high input impedance prevents the circuit from affecting the load terminal. The advantage of using FETs is that it possesses high input impedance. The FETs can also be used in place of the transistor. Thus, in the process of direct coupling, the components required are less which makes the circuit simple and therefore direct coupling is done to reduce complexity. The cascading of the amplifier is done in such a way that the transistors are directly coupled with each other. In the direct coupled amplifier, the transistors are cascaded in order to have higher gain from the amplifier. There are two types of DC Voltmeter according to their construction one is direct coupled Amplifier DC Voltmeter and Chopper type DC Voltmeter. Either transistor or field effect transistor (FET) is used for designing of the multi-stage amplifier. The use of attenuator is to select the voltage range. The DC voltage which is to be measured is applied to the attenuator. The working procedure of DC voltmeter starts with an attenuator. The DC voltmeter measures peak value of DC Voltage applied to it. The AC voltmeters possess non-linear characteristics due to this the measurements obtained at lower voltages are not accurate.ĭC Voltmeter comprises an attenuator, multistage DC amplifier and a permanent magnet moving coil meter. The AC voltmeter consists of attenuator, followed by a rectifier, a multistage amplifier and a PMMC meter. The DC voltmeter consists of attenuator, followed by a multistage amplifier and a PMMC meter. DC Voltmeter measures the peak value of DC voltage.ĪC Voltmeter measures the rms value of AC voltage.