A galvanometer is an instrument used for measurement of intensity of the electric flow. Its structure is based on the properties of magnetic phenomena.

General description

The galvanometers have a needle that, through a spring, is linked to the axis of rotation of a coil. This coil, in turn, has a soft iron core and is located between the opposite poles of a magnet. This fixed magnet generates a uniform magnetic field, in which the coil is located.


The galvanometer is used to measure the intensity of small electrical currents

In this way, when an electric current circulates through the coil of the galvanometer, forces are produced that make it rotate and lead it to move the needle that is linked to its axis thanks to the spring. The movement of the needle reflects, in a scale, what is the intensity of the current in question. Finally, when the flow of current stops, the needle returns to its original position by the action of the spring, which is shaped like a spiral.

Uses, recommendations and more

The galvanometer is used to detect if there is a small electrical current in a circuit. If that current exists, it can also be measured. Its use occurs both at the domestic level and on an industrial scale.

It is important to bear in mind that, before a overload electric, the galvanometer may break. The damage caused by this situation is irreparable.

It should be noted that a ammeter is a kind of galvanometer that has a resistance in parallel. To measure the intensity, the ammeter is connected in series with that crossed by the current.

Galvanometer history

The physicist and chemist Hans Christian Ørsted, a native of Denmark, went down in history for having succeeded in isolating aluminum and having described the relationship that exists on a physical level between electricity and magnetism. More precisely in regards to the galvanometer, he was the first known person who managed to deflect the needles of a compass using current that passed through a piece of wire. This took place in the year 1820.

In fact, that same year, a physicist and chemist named Johann Salomo Christoph Schweigger, first described a device that offered the same functionality as a galvanometer, at the University of Halle. Another of the most relevant names in this field is André-Marie Ampère, a physicist of French origin who made important contributions. The first tests carried out by these and other scientists achieved an increase in the effect of magnetic field using a wire bent many times, a characteristic that inspired the name “multiplier.”

Earth's Magnetic Field Galvanometer

The first galvanometers had to be oriented to the earth’s magnetic field

It was not until 1836 that people began to speak of a “galvanometer”, as a result of the work he carried out Luigi galvani, a researcher from Italy who carried out several experiments to make better use of electric current. The first galvanometers were called “tangents” and were characterized by relying on the earth’s magnetic field to reset the compass needle; it was necessary to orient them before using them. Over time the “static” arose, which had a magnet located in a certain way, and could be used regardless of its orientation.

There was also the mirror galvanometer, created by the physicist and mathematician William thomson, also know as Lord Kelvin. Its design was more fragile and did not use a needle, but several very small magnets that were attached to a lightweight mirror, which was held in suspense with a thread. Broadly speaking, this device it deflected a beam of light, which was greatly magnified by the currents. It was also possible to use a microscope to look at the deflection. Several more decades passed, until in 1888 the American photographer Edward weston began to market a galvanometer with the characteristics of the current ones.