ManufacturerLeeds & Northrop CO.
Place ManufacturedPhiladelphia, U.S.
|Other number||7553||"Catalog Number" printed lower right top|
Dimensionsoverall: 7 1/4 in x 19 1/4 in x 12 1/2 in
DescriptionObject is a metal case bearing five small and four large control knobs, a row of five push-buttons, and a row of 16 binder posts. A printed label reads "TYPE K-3 UNIVERSAL POTENTIOMETER". In the center is a dial that can be set, using the four large knobs, to read any value from 00000 to 15999. One of the knobs moves a decimal point, so that the reading can be 0.015995, or 0.15995, or 1.5995. This probably represents a resistance in ohms (based on, one, the label "potentiometer" and two, that when turning the knob for the last two digits, you can feel it is operating a slider moving over a coil). But if ohms, the precision is truly amazing, anything from 1.6 ohms down to 0.000001 ohms in steps of 1/10000 unit. A card with typewritten notes on two standard voltages was clamped under three of the binder posts (removed into a bag attached).
Searching the internet for "universal potentiometer" finds (http://www2.humboldt.edu/scimus/HSC.54-70/Descriptions/L&NK3Pot.htm, retrieved 2014-10-29) which reads in part:
"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....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."