Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Reflecting Galvanometer, High Sensitivity, Type R

Leeds & Northrup Co.


Humboldt State College; 1960

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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.

This instrument was used by students in the physical/analytical chemistry laboratory at HSU for sensitive measurements in conjunction with the L&N K-3 Potentiometer.

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


The instrument is 9" high with the base 5" in diameter. This particular instrument has a flat-black finish on the aluminum case, a heavy Bakelite base, and a chrome-plated knurled head for the clamping and adjusting shafts. A 70,000 Ohm critical damping shunt resistor is in place across the input. The mirror in this instrument is 3/8" dia, as opposed to the 1/2" mirror in the lowere sensitivity instruments described in the Cenco catalogs below. The serial number, 55953, is engraved in white on the front of the base below the window. A white plastic oval tag folds out from beneath the serial number on the base with specifications handwritten in for this instrument:
SENS. .00003 uA/MM
C.D.R.X. 70000 [ohms]
PERIOD 23.5 Sec
RESIS. 831 [ohms]
CAT. NO. 2285F
There is a yellow decal on the base: STATE OF CALIFORNIA/ HUMBOLDT COLLEGE / 30408. A No. 2178 Prism by L&N used in the P-Chem lab is in storage.


A similar instrument (Type R) is illustrated and described on p736 of the Cenco 1960 Catalog (J-300) and on p 1275 of the 1950 Cenco Catalog (J150).

From the Analytical/Physical Chemistry Lab - Exhibit Catalog

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HSTC (1921-34)
HSC 54-73 icon
HSC (1954-1973)
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HSC (1935-1953)

HSC 1956-72 Instrument Collection

© R. Paselk
Last modified 2 June 2014