Signedengraved on metal plaque on brass case: SIR W. THOMSONS / PATENT / NO 22 / J. WHITE. GLASGOW
engraved on second metal plaque on brass case: J.W. QUEEN & Co. / SOLE AGENTS / PHILADELPHIA. U.S.A.
FunctionThe multicellular voltmeter was developed by William Thomson (Lord Kelvin) in 1887 (patented 1888) to measure high voltages. This electrostatic voltmeter consists of fixed and movable metal plates, which form a condenser. A dumbell needle suspended between the plates is rotated by electrical attraction to the charged conducting plates, and the angle of rotation can then be used with a calibration chart to obtain the potential difference to be measured.
ProvenanceFrom the Department of Physics, Harvard University, 12/12/1956.