- An instrument utilized for measuring and indicating small currents. A moving-coil galvanometer, for instance, utilizes a small wire coil which is suspended or pivoted in a fixed magnetic field. The current that passes through the coil produces a magnetic field which interacts with the fixed field, and the resulting movement of the coil is correlated to a calibrated scale. Depending on the needs, there are specialized galvanometers. For instance, a ballistic galvanometer is designed to respond to rapid current pulses.