When I spent a day in March photographing portions of the Garland Collection of Classical Physics Apparatus at Vanderbilt University, I photographed quite a number of galvanometers. The small motions of the needles are amplified by means of a beam of light reflecting from the small mirror between the two sets of needles. The advantages of a digital instrument are higher precision and accuracy, but factors such as power consumption or cost may still favour application of analog meter movements. The coil twists, pushing against the spring, and moves the pointer. The magnetic needle is free to rotate in the horizontal plane. He developed a method of stabilizing the magnetic field of the permanent magnet, so the instrument would have consistent accuracy over time.

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For example, they enabled long range communication through submarine cables, such as the earliest Transatlantic telegraph cablesand were essential to discovering the electrical activity of the heart and brainby their fine galvaometer of current.

The earliest galvanometer was reported by Johann Schweigger at the University of Halle on 16 September Arbitrary waveform generator Digital pattern generator Function generator Sweep generator Signal generator Video-signal generator.

These capabilities to translate different kinds of electric quantities, in to pointer movements, make the galvanometer ideal for turning output of other sensors that outputs electricity in some form or anotherinto something that can be read by a human.

From the angle read from the compass’s scale, the current could be found from a table.

The numerical value of galvanometer, differential in Chaldean Numerology is: The Hampden-Sydney instrument in the second row is by A. This article needs additional citations for verification. Retrieved 26 April The unmarked differential galvanometer at the right is in the apparatus collection at Case Western Reserve University in Cleveland, Ohio.


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The differentiwl needle is free to rotate in the horizontal plane. A major early use for galvanometers was for finding faults in telecommunications cables.

The coils on the other side can be connected to a separate circuit, thus making the instrument a differential galvanometer. An iron tube between the magnet’s pole pieces defined a circular gap through which the coil rotated.

differential galvanometer

A meter can be calibrated as a DC voltmeter if the resistance of the coil is known by calculating the voltage required to generate a full scale current. On one diffferential, the upper and lower coils are connected in series, with the current passing through them in opposite directions.

In a device called an oscillographthe moving beam of light was used, to produce graphs of current versus time, by recording measurements on photographic film.

When a direct current DC flows through the coil, the coil generates a magnetic field.

Differential Galvanometer

Top view of a tangent galvanometer made about John Wiley and Sons. By using this site, you agree to the Terms of Use and Privacy Policy. This field strength can be calculated from the current as measured by the ammeter, the number of turns of the coil, and the radius of the coils. Open loop, or resonant mirror galvanometers, are mainly used in some types of laser-based bar-code scanners, printing machines, imaging applications, military applications and space systems.


Early designs increased the effect of the magnetic field generated by the current galvanoneter using multiple turns of wire. The story of electrical and magnetic measurements: The taut-band movement is a modern development of the D’Arsonval-Weston movement.

Originally, the instruments relied on the Earth’s magnetic field to provide the restoring force for the compass needle.

Initially laboratory instruments relying on the Earth’s own magnetic field to provide restoring force for the pointer, galvanometers were developed into compact, rugged, sensitive portable instruments essential to the development of electro-technology. Closed-loop mirror galvanometers are also used in similar ways in stereolithographylaser sinteringlaser engravinglaser beam weldinglaser TVslaser displays and in imaging applications such as retinal scanning with Optical Coherence Tomography OCT.

Electrical and electronic measuring equipment.

Galvanometer – Wikipedia

Almost all of these galvanometers are of the moving magnet type. He developed a method of stabilizing the magnetic field of the permanent magnet, so the instrument would have consistent accuracy over time.

Galvanometer mechanisms are divided into moving magnet and moving coil galvanometers; in addition, they are divided into closed-loop and open-loop – or resonant – types. To avoid errors due to parallax, a plane mirror is mounted below the compass needle. The closed loop is obtained measuring the position of the rotating axis with an infrared emitter and 2 photodiodes.