The first galvanometer was built in Germany by Johann S. Schweigger in 1820. It is a device used to measure low-level electric currents by electromechanical action. A mirror galvanometer is a mechanical meter that senses electric current, except that instead of moving a needle, it moves a mirror. In the D'Arsonval design the coil has many turns of fine wire, and is suspended by a flat ribbon of wire which serves as one lead-in wire.

Although many have been replaced by electronic instruments, galvanometers have been a basic instrument to measure electric current and many types of galvanometers have been developed for particular sets of electrical instruments. Instrument makers have strived to produce more sensitive galvanometers and the D'Arsonval design represents a stage of innovation in these types of instruments.

Other reflecting galvanometers in the Museum's collection range from 1906 to the late 1920s.

Written by Erika Dicker
Assistant Curator, 2007.

This galvanometer was made by Leeds & Northrup Co, in Philadelphia, Pennsylvania, United States of America, 1938-1946.

Leeds & Northrup was established in 1903 when Edwin Northrup joined the Morris E. Leeds Company. Leeds & Northrup was bought out by the Foxboro Company, now called APV Australia Pty Ltd.

This is a portable, D'Arsonval type moving coil reflecting galvanometer, contained in a painted grey wooden box, with two sets of terminals mounted on the exterior of the box, two for connection of a 6-volt AC or DC power source, and the other two for test connection.

The top of the box hinges back to show a horseshoe magnet lying horizontally. The galvanometer system is a light coil assembly with a pivotable mirror suspended between the poles of the horseshoe magnet.

D'Arsonval type galvanometers operate by means of a light coil of wire being suspended from a metal ribbon a few thousandths of a millimetre wide and less than 0.02mm thick. The light system comprises a lamp, lamp-holder and lens assembly. Mirror and light assembly operate in the same plane, to reflect the light beam on to a frosted glass panel on the front inside of the box. The glass panel is marked with a scale graduated in millimetres. The coil, which can freely rotate between the permanent magnet poles carries the small mirror which acts as the optical pointer, showing the coil position. Current is conducted to and from the coil by the suspension ribbons.

A galvanometer is an instrument for detecting and measuring electric current. It is an electromechanical transducer that produces a rotary deflection through a limited arc in response to electric current flowing through its coil.

Made: Leeds & Northrup Co; ; 1938 - 1946

Information on badge attached to lid 'LEEDS & NORTHRUP CO. / PHILADELPHIA PENNSYLVANIA / MADE IN U.S.A.'. Beneath this, 'CAT. NO. 2420 A', the Leeds and Northrup logo and 'SERIAL NO. 1114281'.

2007/169/1

1938 - 1946

137 mm

140 mm

220 mm