The ammeter is connected in the charging circuit between the battery and generator to show how much current is f flowing to the battery during the charging: and how much current is flowing from the battery during the discharging. The ammeter is fitted on the instrument panel in front of the driver. It is used in most of the vehicles. however, an indicator lamp is also used in some vehicles to indicate whether or not the generator is charging the battery.
The figure shows the simplified diagram of a car ammeter. It consists of a pivoted vane to which a needle is attached, a permanent magnet and a heavy conductor. The needle moves on a graduated scale, one side of which indicates charging current and the other side discharging current. At the centre, zero is marked. When the needle points zero, no current flows to or from m the battery, the pivoted vane is held between the two poles of the permanent magnet When the current flows to the battery, needle swings to “charge” side.