Humboldt State University

Robert A. Paselk Scientific Instrument Museum

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Weston D.C. Voltmeter, Model 45

Weston Electrical Instrument Corp.

Newark N.J.

31786

Humboldt S-T-C; c.1926

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Usage/History

Instruments such as this were used by trained technical/scientific staff for precision laboratory measurements of voltage, and as secondary standards for calibrating other meters. The mirrored scale makes it easier to read the instrument to a given accuracy by enabling the operator to avoid parallax errors. Note that this particular instrument has been standardized at the factory and was certified accurate to ±0.5% of full scale, or in this case ±0.075 volts.

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

Description

The instrument in housed in a 7.75 x 7.75 x 4.5" oak case with a leather handle. All hardware is nickel-plated brass. The front panel and meter face plate are of heavy cast iron with a fine diamond pattern on the casting. Iron parts have a "japanned" black enamel finish. The binding posts are of black Bakelite. The meter has a mirrored scale. The serial number is hand written on the white scale behind the face plate. The top screw holding the face plate in place is sealed with sealing wax(?) and stamped with a "W." There is a brass plate finished in black and nickel plating attached to the front of the cabinet below the door:

 
MADE BY THE
WESTON ELECTRICAL INSTRUMENT CO.
NEWARK, N.J., U.S.A
PATENTED
NOV. 6, 1888 MAY 14, 1889 APR. 29, 1890
FEB. 17, 1891 DEC. 19, 1893 OCT. 4, 1898
JUL. 18, 1901
MODEL 45 NO 31789
 
Beneath this plate is a brass escutcheon labeled "0 CORRECTION" giving access to the zero correction screw.
 
There is a calibration sheet held under acetate in a black painted brass frame inside the door. It is signed and dated: June 15, 1926. There is an oval brass tag attached with brass brads left side of instrument stamped HUMBOLDT S-T-C / 2100.
 
The oak case has been stripped and refinished with "Watco Danish Oil," all exposed metal parts have been acid cleaned and lightly polished. Bakelite, painted metal, and rubber parts have been cleaned and polished with furniture polish, and the leather handle has been treated with neatsfoot oil.
 
 

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© R. Paselk
Last modified 30 August 2010