Why Does an Ammeter Need a Shunt?

An ammeter is a device that uses electromagnetism to measure current through a circuit. To increase the level of current that can be measured by an ammeter, a shunt is added to the system.

Function

Shunts in an ammeter act as resistors. The current passes through the shunt and the known quantity of resistance across the shunt is used to calculate the level of current.

Significance

Ammeters that might otherwise be overburdened by a high current retain their utility with the addition of a shunt.

History

In the past, shunts bore part of the electrical load and the reading was taken as the percentage of voltage drop across the shunt; this system was found in galvanometers.

Improvements

Many of today's ammeter shunts bear the entire electrical load and the reading is obtained via an analog to digital converter.

Considerations

Because the shunt is used to compensate for an ammeter's narrow reading range, a faulty shunt may cause damage to the ammeter.