An instrument used to detect and measure very small electric
currents. Most modern galvanometers are of the moving-coil type in which
a coil of fine wire wrapped around an aluminum former is suspended by conducting
ribbons about a soft iron core between the poles of a permanent magnet.
When a current flows through the coil, a magnetic
field is set up which interacts with that of the permanent magnet producing
a torque. This turns the coil until it is
fully resisted by the suspension, the displacement produced being proportional
to the current. The result is read from a scale onto which a light beam
is reflected from a mirror carried on the suspension ribbons.
|Principle of the moving-coil galvanometer
If all electromagnetic and mechanical damping can be eliminated from such
an instrument, it can also be used as a ballistic galvanometer to measure
small charges and capacitances.
See also ammeter.