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ID number:  BIRRC-P0199
Institution:  Research and Cultural Collections
Named collection:  Historic Physics Collection
Artist / Maker:  The Cambridge Scientific Instrument Co. Ltd.
Title / Object name:  Duddell oscillograph
Object type:  Electrical instrument
Place made:  Cambridge, England
Date made:  1909
Materials:  Lacquered brass body and black steel permanent magnet with many other components including a thermometer
Measurements:  17 x 17 x 25 cm
BIRRC-P0199a.jpg

This oscillograph is an early instrument for recording the waveform of electrical signals up to about 300 Hz. It is essentially a moving coil galvanometer in which the coil is a long narrow single loop of wire held under tension in the magnetic field. The coil has a short time constant and is damped by being immersed in oil. A mirror is attached to the coil and from it a light beam would be reflected onto a falling plate or cinematograph camera (not included in the collection). There are in fact two such coils side by side so that two waveforms can be compared. The thermometer records the temperature of the oil, which affects the performance.
This is a Type 2 instrument cat. no. 202/45121 originally costing £35.

Inscriptions / Translations:  THE CAMBRIDGE SCIENTIFIC INSTRUMENT CO. LTD.
CAMBRIDGE ENGLAND
NO 7998
DUDDELL’S PATENT
UK 5449 1898
B’HAM UNIV PHYSICS
E 289

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