Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Weston A.C. Voltmeter, Model 155
Weston Electrical Instrument Corp.
provenance: 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 user to avoid parallax errors. This particular instrument was specified to be accurate to ±0.5%.
The instrument in housed in a 71/8 x 6 3/4 x 3 1/4" walnut case with a leather handle on top. All hardware is nickel-plated brass. The front panel has a window cut into it to view th emeter face. The meter has a mirrored scale. The serial number (32646) is hand written on the white paper scale behind the face plate. The two screws in the side of the case allowing access to the movement are sealed with black sealing wax(?) and stamped with a "W." The instrument has four rubber feet on the bottom for storage and four more feet (one missing) on the back for use during operation. There are two Bakelite binding posts on the left side of the instrument's case, and a momentary contact switch with a vulcanite button on the lower right side of the front.
Beneath window is a brass escutcheon labeled "0 CORRECTION" giving access to the zero correction screw. There is a brass plate finished in black and nickel plating attached to the front of the cabinet below the escutcheon: