Description

This voltmeter is housed in a wooden case with a hinged lid that opens to reveal a metal box attached to the top half of the wooden case. That metal box has an arc-shaped window that opens onto a white scale. The scale is graduated linearly from 0 to 150 (volts). There is an arc-shaped mirrored strip below the scale, and a thin indicator needle resting on 0. This instrument has four electrical connectors on the top: the two on the left corner are labeled 750 and 300, and the two on the right corner are labeled 150 and +. The inside cover of the lid has a metal frame that holds a piece of paper with information about the instrument and its standardization information. It was standardized at the Weston Laboratory on May 10, 1926. Serial number 30705.

Voltmeters measure electric potential difference (or voltage) between two points in an electric circuit. This one was used in the MIT Electrical Engineering Department.