Humboldt State University ® Department of Chemistry
Robert A. Paselk Scientific Instrument Museum
A.C. Milliammeter, Model 931
Weston Electrical Instrument Corp.
Humboldt State College, c.1960
For laboratory, production and general testing of DC currents. These are top-of-the-line, hand-calibrated, meters for regular use, and may function as secondary standards for routine applications. Note the mirrored scales and knife edged needles designed to eliminate parallax reading errors. For highest accuracy they would be used horizontally, and thus have feet on the back as well on the bottom of the case.
The meter has a molded black bakelite case 3 1/4" x 5" x 5 1/4". There is a black leather carrying strap. The meter has a mirrored scale and knife-edge pointer. This model has a triple range (0-0.15; 0-1.5, & 0-15 mA) chosen by binding posts on the top of the meter. Model 931 meters have a rated accuracy of 0.5% of full scale when used in the horizontal position. Decal (now removed): STATE OF CALIFORNIA / HUMBOLDT COLLEGE / 30?86.
Research: These meters are described in The 1960 (J-300) Cenco
Catalog, pg 748, as Weston Model 931 meters. They also appear
on pg 536 of the 1976 Central Scientific Catalog.
HSU Physics Department, discarded Fall 1990.