A galvanometer is an instrument for measuring electrical current. It works based on the magnetic force that causes a needle to turn, and its movement is directly proportional to the intensity of the electric current in the circuit. Galvanometers can measure the intensity and direction of electrical current. They are used to prevent devices from experiencing electrical overload by measuring the intensity of an electrical current and monitoring it. Galvanometers can be used in both domestic and industrial environments.

Galvanometers have the same parts that make it possible to measure the flow of an electrical current with precision:

• Coil: the part of the galvanometer through which the electric current to be measured travels.
• Spring: the joint between the coil and the needle that gives the measurement.
• Needle: the part that indicates the value of the measured electric current.

The most common type of galvanometer is the D’Arsonval galvanometer. It consists of a light coil of wire suspended from a metallic ribbon between the poles of a permanent magnet. The magnetic field produced by a current passing through the coil reacts with the magnetic field of the permanent magnet, producing a torque, or twisting force. The coil, to which an indicating needle or mirror is attached, rotates under the action of the torque. The angle through which it rotates to balance the torsion of the suspension provides a measure of the current flowing in the coil. The angle is measured by the movement of the needle or by the deflection of a beam of light reflected from the mirror.

Galvanometers can measure more current than is passing through them by putting a shunt in parallel to them. After putting a shunt in parallel to a galvanometer, it becomes an ammeter. Each division of scale in an ammeter will be showing higher current than that of a galvanometer. If we know the current that the galvanometer is measuring, we can calculate the current that is passing through it.