Ammeter

Ammeter is a device for measuring current in amperes. The scale of ammeters is calibrated in microamps, milliamps, amperes or kiloamps in accordance with the measurement limits of the device.

Pic. 1. Ammeter

In an electrical circuit, the ammeter is connected in series with the section of the electrical circuit in which the current is measured.

This connection leads to a change in the circuit (the resistance of the ammeter is added) in which the current is measured. Therefore, it is not the true value of the original current in the circuit that is measured, but a slightly underestimated value.

Therefore, the lower the internal resistance of the ammeter (ideally 0), the less influence the device will have on the object under study, and the higher the measurement accuracy will be.

To measure large currents in power circuits, measuring current transformers and external measuring current shunts are also used.

Pic. 3. Current Transformer

Pic. 4. Current Shunt Resistor or Ammeter Shunt

Ammeters based on the Hall Effect are also used to measure current. Such ammeters have two parts - 1 - measuring clamps and 2 - the ammeter itself. The great advantage of such a device is that there is no need to break the measured circuit.

Pic. 5. Ammeters based on the Hall Effect

The ammeter should also be considered as a mode of operation of a multimeter.