What is a Voltmeter?
A voltmeter is a device used to measure the voltage potential between two points in an electrical circuit. First created in the early 1800s, voltmeters were originally called galvanometers. Technically, all voltmeters are ammeters, as they measure current rather than voltage. Although current is measured in amps, Ohm’s Law, which establishes the relationship between voltage, current and resistance, can be used to scale the amps to volts. Voltmeters were made possible by an 1819 discovery by Hans Oersted. When he passed a current through a wire near a compass needle, he noticed the needle would change direction. The earliest attempts to take advantage of this effect were little more than a coil of wire wrapped around a compass; the stronger the current passing through the wire, the greater the deflection of the compass needle. While functional, these early models were not very accurate. In the late 19th century Arsene D’Arsonval discovered the instrument could be made much more responsi
