TitleDirect current microammeter, Weston Instruments Inc. Model 622Date11th July 1966About this objectThe Weston Model 622 is a precision direct current (DC) microammeter used to measure extremely small electrical currents down to millionths of an ampere. Instruments like this were essential in testing and maintaining telegraph and communication circuits, where even minute current variations could affect signal transmissions over long distances, especially in submarine cables.
Unlike standard ammeters that measure current in the milliampere range or larger currents, this device offered the fine sensitivity that could detect leakage, short circuits and other anomalies. Its metal case and leather strap indicate the microammeter was designed as a portable field instrument.
Founded in 1888 by Edward Weston, the Weston Electrical Instrument Company was the first to develop accurate portable, direct-reading voltmeters, ammeters and light meters, and went on to manufacture various other precision electrical measuring instruments for laboratory, industrial and commercial use. Object No.99.78CreatorWeston Instruments Inc.Inscriptions & marksCase exterior engraved with Weston brand logo; ‘WESTON 622’ on metal case; paper label inside lid reads: ‘WESTON D. C. MICROAMMETER, MODEL 622 / This instrument indicates ABSOLUTE MICROAMPERES and is correct within 1/2 of 1 per cent of full scale value at any part of the scale at 25°C. For ordinary measurements no temperature correction is required. If greater accuracy is desired at temperatures other than 25°C., apply correction formula given below. / Microampere Range / Resistance Ohms at 25°C / To correct for temperature multiply readings by / WESTON INSTRUMENTS, INC., NEWARK, N.J., U.S.A. / Serial No. 31942 / Date JUL 11 1966. Certified (Eligible signature)' / Printed in U.S.A. DimensionsH: 230mm
W: 214mm
D: 102 mmPlace madeNewark, N.J., U.S.SourceLa Perouse MuseumOn displayNoTypeMuseum objectsOrganisations (Detailed entries)La Perouse Museum (La Perouse, N.S.W.)ThemesScience and communication
Weston Instruments Inc., Direct current microammeter, Weston Instruments Inc. Model 622 (11th July 1966). Randwick City Council, accessed 25/01/2026, https://ourstory.randwick.nsw.gov.au/nodes/view/12394
