Description

Analog ammeters, also known as current meters, are metered instruments that measure current flow in amperes. Current levels are displayed on a dial, usually with a moving pointer or needle made of soft iron. Analog ammeters provide information about the current draw and current continuity in order to help users troubleshoot erratic loads and trends. They have both positive and negative leads and feature extremely low internal resistance.

They are required to measure the current in a circuit and are therefore connected in series with the components carrying the current. High current flow may indicate a short circuit, unintentional ground, or defective component. Low current flow may indicate high resistance or poor current flow within the circuit. If the ammeter resistance is not significantly smaller than the load resistance, the load current can be substantially altered by the inclusion of the ammeter in the circuit.

For higher range ammeters, a low resistance made up of manganin (low-temperature coefficient of resistance) is connected in parallel to the moving coil and the instrument may be calibrated to read directly to the total current. This type of ammeter is called a shunt. The shunt method is typically used for higher currents as the coil of the movements can only handle small currents directly.