Galvanometer, an electrical measuring instrument of high sensitivity for measuring small currents, voltages and quantities of electricity (see Ballistic galvanometer). It is widely used as a null indicator, to establish the absence of current in an electric circuit or a zero potential difference between any two points of a circuit. The most widespread is the direct-current galvanometer with a magnetoelectric measuring mechanism. To raise its sensitivity, optical reading devices are used, with a remote scale placed at a considerable distance from the moving part of the mechanism, or else a special optical system with multiple reflection of a light beam is employed. The sensitivity of a galvanometer and the character of the motion of its moving part depend on the resistance of the external electric circuit across which the galvanometer is connected. In practice galvanometers are characterised by the reciprocal of the sensitivity, the so-called galvanometer constant. (b). The documentation gives the value of b at an external resistance equal to the critical one, at which the motion of the moving part passes from oscillatory to aperiodic. In modern direct-current galvanometers the values of b reach: in current 10-12 A*m/mm, in voltage 3*10-8 V*m/mm. In alternating-current circuits of low frequency (from 30 to 100 Hz) vibration galvanometers are used. (see Vibration electrical measuring mechanism) with constants in current down to 10-8A/mm and in voltage down to 2*10-5 V/mm.
The technical requirements for galvanometers are standardised in GOST 22261—76 and GOST 7324—80.
The technical requirements for galvanometers are standardised in GOST 22261—76 and GOST 7324—80.