What is a Voltmeter?

Instruments that measure the voltage value in a circuit are collectively called voltmeters, also known as voltmeters. Voltmeters can be divided into millivoltmeters, voltmeters, kilovoltmeters, etc. according to their ranges and calculation units, and symbols such as mV, V, and kV are marked on their dials. Voltmeters can be divided into DC voltmeters and AC voltmeters according to the nature of the voltage being measured. The AC voltmeter is shown in Figure 3-2.

Since the voltmeter and the circuit being measured are connected in parallel, the internal resistance of the voltmeter is generally large in order not to affect the working state of the circuit. A large-range voltmeter usually has a resistor connected in series to reduce the current passing through the voltmeter proportionally. This resistor is called a multiplier resistor.

Some are installed inside the meter, and some are installed outside the meter and used in conjunction with the meter. The dial is marked with the words "external resistor". The external resistor is an accessory of the meter, and the meter cannot be used without it.