Signedprinted on instrument display: ACME ELECTRIC WORKS; and: Aryton and Perry
Inscribedscale printed on instrument dial: 0 - 500;
printed on the dial: VOLTS / ARYTON & PERRY's / DIRECT READING / SPRING VOLTOMETER / PATENTED 1883 / THE ACME ELECTRIC WORKS / FERDINAND ST. LONDON N° R32;
printed around center of dial: J.W. Queen & Co. / American Agents
FunctionThe Ayrton and Perry ammeter, introduced in 1883, was the first ammeter that could give direct readings of currents without the need of further calculation. The Ayrton and Perry voltmeter was a modification of the ammeter with a large resistance.
Historical AttributesPhysics Dept.
Related WorksThe Ayrton and Perry direct reading ammeter, of which the voltmeter is a slight modification, is described in:
Robert Bud and Deborah Jean Warner, Instruments of Science: an Historical Encyclopedia , Taylor and Francis (1998). pp. 22-23.