02-12-2017, 10:53 AM
A galvanometer is an electromechanical instrument to detect and indicate electrical current. A galvanometer works like an actuator, producing a rotating deflection (of a "pointer"), in response to electrical 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 electrical circuit.
The galvanometers were developed from the observation that the needle of a magnetic compass is deflected near a cable that has an electric current flowing through it, first described by Hans Oersted in 1820. They were the first instruments used to detect and measure small amounts of electric currents. André-Marie Ampère, who gave mathematical expression to the discovery of Ørsted and appointed him by the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frogs galvanoscope, that electric current would cause the legs of a dead frog to shake.
Sensitive galvanometers have been essential for the development of science and technology in many fields. For example, they allowed long-range communication through submarine cables, such as the first transatlantic telegraph cables, and they were essential to discover the electrical activity of the heart and brain, by their precise measurements of the current.
Galvanometers also had a widespread use as a visualizing part in other types of analog meters, for example in light meters, VU meters, etc., where they were used to measure and display the output of other sensors. Nowadays, the main type of galvanometric mechanism, still in use, is the mobile coil, type D'Arsonval / Weston.