Humboldt State University

Robert A. Paselk Scientific Instrument Museum

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Reflecting Galvanometer, Current

Leeds & Northrup Co.



Humboldt S-T-C; c.1926

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The reflecting galvanometer is a sensitive instrument for measuring current. It consists of a magnet coil with an attached mirror suspended between the poles of a magnet by a thin gold ribbon above and a coiled gold wire below. When an electric current is introduced into the magnet coil it induces a magnetic field, causing the coil to rotate in proportion to the current. The mirror allows the user to see very small deflections, and thus to measure very small currents, by observing a distant reflected scale (one meter or more away) through a telescope. The instrument is mounted on an optional leveling base of cast iron.

Some contemporary/early descriptions of the Galvanometer and its use are provided below:


L&N Type P, current, student grade moving coil reflecting galvanometer, serial number 102521. The meter consists of a 7 1/8 x 4 5/8 x 7/8" magnet covered by a bronze plate with a center 1 3/4 x 3 3/8" window and with a hollow suspension post of nickel plated brass (4 1/4 x 3/8") on top. The L&N logo is in polished raised letters against a black painted background, with raised polished borders around the edge and the window. The coil is stabilized with wax, the mirror is 5/8" dia. The meter is mounted on 6 1/4 x 9 x 3/4" mahogany backboard with two nickel plated brass hangers at the top, two black painted telescope arm brackets on the sides, two Bakelite binding posts at the bottom on either side of a leveling screw, a manufacturers label on the bottom edge and a brass Humboldt S-T-C tag (2120) on the lower right hand corner. The leveling screw is a replacement from a more recent model of the same instrument. The tripod galvanometer base is of heavy cast iron with a japanned finish. There are three brass & Ebonite leveling screws.

HSTC Instrument Collection

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HSTC (1921-34)
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HSC (1935-1953)
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HSC (1954-1973)

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© R. Paselk
Last modified 30 August 2010