Galvanometer

A galvanometer is an electromechanical instrument used for detecting and indicating electric current.
A galvanometer works as an actuator, by producing a rotary deflection (of a “pointer”), in response to electric current flowing through a coil in a constant magnetic field.
Early galvanometers were not calibrated, but their later developments were used as measuring instruments, called ammeters, to measure the current flowing through an electric circuit.
Today the main type of galvanometer mechanism, still in use, is the moving coil.
Galvanometers also had widespread use as the visualizing part in other kinds of analog meters, for example in light meters, VU meters, etc., where they were used to measure and display the output of other sensors.