Ammeter – An Aircraft Ammeter is an instrument installed in series with an electrical load used to measure the amount of current flowing through the load. The unit of measure is the ampere.
Shown is an Aircraft Ammeter /Loadmeter combination.
Purpose of the Ammeter
An ammeter is used to monitor the performance of the aircraft electrical system. The ammeter shows if the alternator/generator is producing an adequate supply of electrical power. It also indicates whether or not the battery is receiving an electrical charge. Ammeters are designed with the zero point in the center of the face and a negative or positive indication on either side. When the pointer of the ammeter is on the plus side, it shows the charging rate of the battery. A minus indication means more current is being drawn from the battery than is being replaced. A full-scale minus deflection indicates a malfunction of the alternator/generator. A full-scale positive deflection indicates a malfunction of the regulator. In either case, consult the AFM or POH for appropriate action to be taken
Not all Aircraft have an Ammeter
Not all aircraft are equipped with an ammeter. Some have a warning light that, when lighted, indicates a discharge in the system as a generator/alternator malfunction. Refer to the AFM or POH for appropriate action to be taken.
In an AC circuit, a voltmeter indicates the effective voltage and an ammeter indicates the effective current. The product of these two readings is called the apparent power.
The Diagram below illustrates the Ammeter position in the aircraft electrical system.