DC voltmeter

This type of DC voltmeter, from around 1900, is part of a whole series of different moving coil meters for current and voltage produced by the Weston Electrical Instrument Corporation. Its operation is based on sending a flow of current through a swivel-mounted coil with a pointer needle. This coil is placed between the north andsouth poles of a permanent magnet. It is one of the first robust, portable meters that was shielded against magnetic interference from the environment. The meter is mounted in, and partially on, a wooden cabinet. At the bottom left are two connection terminals for voltages up to 150 and 300 volts respectively. In both cases, the reference terminal at the bottom right is used. Above this connection is a push button for switching the meter on and off.