Analog Voltmeter

Analog voltmeters measure voltage or voltage drop in a circuit. They display readings using a needle rather than a digital display. Voltmeters may be standalone devices or a part of a multimeter.

Analog voltmeters use a wide variety of means to measure voltage, with d’Arsonval moving-coil galvanometers being the most common. These devices use a coil of fine wire suspended within a magnetic field. The coil rotates and moves a pointer or other indicator proportional to the applied current level.

Moving-coil galvanometers are typically used to measure current in ammeters, but when provided with suitable resistance can also measure DC voltage in voltmeters. They are desirable due to their superior sensitivity but are unsuitable for AC measurement because they are responsive only to average current flow. Moving-coil voltmeters may accurately measure AC voltage if they are fitted with a rectifier and transformer.

A second voltmeter type uses taut-band suspension, which also employs a moving coil. Taut-band meters eliminate the pivot and jewel mechanism employed by d’Arsonval meters and replace it with a twisting platinum band. This setup mitigates friction, which is the cause of wear and repeatability problems in moving-coil instruments.

Applications

Digital voltmeters have generally superseded analog types, but the latter still finds widespread use in niche applications such as:

• Battery indicators, especially in marine or naval craft
• Pulse or oscillation measurement, in which the movement of the indicator is more important than the precise voltage value