Campbell vibration galvanometer with moving coil
Date: circa 1930
Inventory Number: 0225
Classification: Galvanometer
Subject:
Maker: Cambridge Instrument Company, Ltd. (1924 - 1968)
User: Department of Physics, Harvard University (founded 1884)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
33.7 x 20.3 x 20.3 cm (13 1/4 x 8 x 8 in.)
Description:
Campbell's type galvanometer with bifilar suspension above and below small coil, mirror and spring in fixed circular magnet. Cylindrical brass cover with circular viewing window. Brass suspension tube with horizontally-mounted brass knob for adjusting vibrational wires. Round, black brass base with two brass leveling screws and one binding post. Similar to instrument 0262 in this collection.
Signedon plaque base: CAMBRIDGE / INSTR. CO., INC. / OSSINING, N.Y. / No. ________ ; CAMBRIDGE / INSTRUMENT CO., L.T.D. / ENGLAND / CAMPBELL VIBRATION / GALVANOMETER / No L-36255
Inscribedmarked on edge of base: 225
FunctionThis Campbell's vibration type galvanometer has a mirror supported by a pair of upper and lower strings. A small pulley sheave adjusts the vibrating length of the string and the sheave's position can be moved upwards and downwards with a horizontally-mounted lever that tunes the galvanometer to a resonance frequency that is equivalent to the optimal length of the string. A brass adjustment knob for string tension is mounted next to the lever, and there is a spring to load the tension of the vibrational strings next to the suspension tube. When current is introduced into the string (wire) in the presence of a magnetic field, the string moves.
ProvenanceFrom the Department of Physics, Harvard University, 1/8/1957.