Ammeter

This ampere hour meter sends the current through a magnet, creating a magnetic field. The strength of this field changes in direct proportion to the strength of that current. This magnetic field causes an indicator attached to a small magnet to move in proportion to its strength. A mechanical counter registers the position of the needle every 2.5 minutes and increases the counter accordingly. The meter gives a reading in ampere-hours: a measure of electric charge. This unit is used for purposes such as indicating the capacity of batteries.