Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Weston D.C. Voltmeter, Model 45
Weston Electrical Instrument Corp.
Humboldt S-T-C; c.1926
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.
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: