Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Universal Potentiometer, Type K-3

Leeds & Northrup Co., Philadelphia

Humboldt State College, 1960

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The potentiometer is used to measure voltages by comparison to a known reference voltage. The L&N K-3 universal potentiometer was the top-of-the-line research grade instrument used in industrial and university labs for best quality work. Prior to the development of digital electronics potentiometers were the standard for sensitive and precise voltage measurements required for measureing temperature, pH, conductivity, etc.
The current instrument is composed of a series of precision resistors which may be placed in series with a precision slide-wire resistor to create a resistance of known value. In use the instrument is connected to known and unknown voltage sources, and the resistors are adjusted until the voltages are matched as indicated by a null reading on a sensitive galvanometer. The instrument is also set-up so that the known source may be readily calibrated against a reference voltage source (generally a Weston standard cell). The potentiometer made up the heart of a great number of instruments for measuring such quantities as pH, conductivity, light intensity etc.
Some contemporary/early descriptions of the potentiometer and its use are provided below:


The instrument on display is in excellent, like-new condition. It is described in detail in the Cenco catalog description. The instrument is accompanied by an operating manual that is not on display, but may be viewed by clicking here.

From the Analytical/Physical Chemistry Lab - Exhibit Catalog

 HSTC icon
HSTC (1921-34)
HSC 54-73 icon
HSC (1954-1973)
HSC 35-53 icon
HSC (1935-1953)

HSC 1956-72 Instrument Collection

© R. Paselk
Last modified 13 August 2010