What is a voltmeter?

Basically, voltmeters are standard items on switchboards and control panels. They are basically single-circuit elements so when three phases are to be indicated either three devices are used or one with a multipoint switch. A voltmeter is connected across the line and is high-impedance. The ranges of the voltmeter may be varied in series with high-value resistors; Such resistors are known as voltmeter multipliers. For high voltage, a potential transformer (PT) is connected to the main line called the primary and a voltmeter is connected to the secondary. Voltmeters are usually moving iron. Moving coil meters can also be used but in combination with rectifiers.