Galvanometer

A Galvanometer is an instrument that detects and measures the magnitude of small electric currents. It is a type of electromechanical device that detects the current and indicates its intensity by moving the magnetic needle or coil inside a magnetic field.

Galvanometers play a vital role in the development of various fields in technology as well as science. For example, in the 1800s, they played an important role in facilitating communication via submarine cables, such as the telegraph cables laid transatlantic. Earlier, they were critical in determining the electrical impulses of the brain and heart due to their fine current measurements.

History of Galvanometer

The principle of Galvanometer was introduced in the 19th century. Hans Christian Orsted made the first observations on galvanometers in 1820. He noticed that when a magnetic compass needle makes contact with an electric current-carrying wire, it deflects. This later became the principle of Galvanometer.

These were also the first devices used for identifying and assessing low-level currents. André-Marie Ampère was the first one to put Orsted’s discovery into mathematical form. The name was particularly derived from the surname of Italian electricity experimenter Luigi Galvani because, in 1791, he discovered that electric current could cause a dead frog’s leg to jerk.

Later, Johann Schweigger developed the early Galvanometer on September 16, 1820, at the University of Halle. André-Marie Ampère also played a major role in this innovation. The term “Galvanometer” was in widespread use by 1836. Using multiple turns of wire in early designs increased the effect of the magnetic field generated by the current. Because of this common design feature, the instruments were initially referred to as “multipliers.” 

We can classify Galvanometers into two types. One type of Galvanometer displays measurements with a solid pointer on a scale. The others, which are more sensitive, use a small mirror and a light beam to provide mechanical amplification of low-level signals.

Astatic Galvanometer

It was invented in 1825 by Leopoldo Nobili and consisted of two magnetised needles located parallelly but having their magnetic poles in the reverse direction. A thread of single silk held these needles in place. The dipole moment of the second needle cancelled the dipole moment of the first needle, resulting in the armature having zero magnetic dipole moment and thus being unchanged by the Earth’s magnetic field. The rotation of the needle is opposed by the torsional elasticity of the suspension thread, which is proportional to the angle.

Tangent Galvanometer

A tangent galvanometer is an early measuring instrument used to measure electric current. It works by comparing a magnetic field generated by an unknown current to the Earth’s magnetic field with a compass needle. The tangent law of magnetism, which states that the tangent of the angle made by a compass needle is proportional to the ratio of the strengths of the two perpendicular magnetic fields, gives it its name. Johan Jakob Nervander described it for the first time in 1834.

Mirror Galvanometer

The mirror Galvanometer replaces the pointer with a lightweight mirror to get higher sensitivity in reading very small currents. It comprises horizontal magnets suspended from a thin fibre in a vertical wire coil, with magnets and a mirror attached. The light ray falls across the room on a marked scale, acting as a larger mass-less pointer. In the 1850s, the mirror galvanometer was used to function as a receiver for installing the trans-Atlantic cables for the telegraph. A beam of light was used in an oscillograph to produce current versus time graphs by recording photographic film measurements.

Ballistic Galvanometer

It is a sensitive Galvanometer used to measure the amount of charge passing along it. In contrast to a current-measuring Galvanometer, it functions as an integrator. The part in motion has a very high moment of inertia, which gives it a long enough oscillation period to do the measurement. 

Uses of Galvanometer

The main purpose of a Galvanometer is to measure electricity; it has various applications and is used for different purposes. The other uses of Galvanometer  are:

• Used in modern automobiles and heavy mechanical engineering for positioning and controlling systems.

• Used to detect errors in communications cables.

• It is a moving coil in a permanent magnet. This mechanism is used in various applications, including hard disc drives, actuators, etc.

• Used in analogue strip chart recorders such as polygraphs, electroencephalography, and electrocardiographs to position the pens.

Conclusion

The Galvanometer is a significant development of the 19th century; developed in the 1800’s it has gone through various changes. Galvanometers have applications in automobiles, heavy mechanical engineering, and controlling systems. Based on the principle that a current-carrying coil in a magnetic field experiences a torque that Hans Christian Orsted first observed, this principle of the Galvanometer has become critical to advancing science and technology.