Humboldt State University ® Department of Chemistry
Robert A. Paselk Scientific Instrument Museum
L&N Wheatstone Bridge
Leeds & Northrup Co.Philadelphia
Humboldt State College, c. 1940
Used to determine the value of an unknown resistance. The wood case dates it < 1950.
From WikiPedia: "A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component.
Its operation is similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridge's initial uses was for the purpose of soils analysis and comparison." (http://en.wikipedia.org/wiki/Wheatstone_bridge; downloaded from Wikipedia 06/27/2012)
Early descriptions of the Wheatstone Bridge are provided below:
The instrument is described in the catalog scan available above. The heavy Bakelite top measures 9 1/4" x 6" x 1/2", the base of the mahogany case measures 9 3/4" x 6 1/2". The catalog scan is from Cenco. Cat J-141, General Catalog Laboratory Apparatus & Scientific Instruments.
Chicago. (1941). An image of the controls from the top is provided showing all graduations and L&N serial number etc.
© R. Paselk