What is an Ammeter?

An ammeter is a device used to measure the electric current present in a circuit. The amount of electric current is measured in amperes, from which the meter gets its name. It also has sister meter that measuring a smaller electric circuit called either a milliameter and a microameter.

Early Designs

The earliest ammeter was designed by French physicist Jacques-Arsène d'Arsonval that was known as a galvanometer, or a moving coil ammeter. This measuring device employs the use of magnetic deflection so when a current moves through the coil causing a needle to move. Later devices used a piece of iron that, when acted upon by the electrically charged magnet, would move. This device could record both alternating (AC) and direct (DC) electric currents whereas the moving coil ammeter only records direct.

Large Electric Currents

Large electric currents could not be measured directly with an ammeter. Therefore, a shunt has to be placed parallel to the meter. This shunt is commonly called a resistor and receives most of the current allowing the meter to measure a small flow.

Modern Devices

Today, most ammeters are zero-centered so the amperes can be monitored for both polarities, which is a common practice in testing both industrial and scientific equipment.

Recent technological advances have allowed for the development of a digital ammeter design.