reflecting galvanometer
Datecirca 1930
Inventory Number0264a,b
ClassificationGalvanometer
Subject
Maker
Cambridge Instrument Company, Ltd.
1924 - 1968
User
Harvard Engineering School
1918 - 1951
Cultural Region
Place of Origin
Place of Use
Dimensions33.5 × 20.6 × 22.5 cm (13 3/16 × 8 1/8 × 8 7/8 in.)
Material
DescriptionGalvanometer with helical moving coil set in a permanent magnet. Wide brass suspension tube for string suspension with small circular mirror. Slightly rounded square brass base with four brass cylindrical supports. Base has two brass bubble levels and two brass binding posts. Wooden case with four binding posts on top and rectangular brass-framed glass viewing window fits over galvanometer. Four (?) pointed brass leveling screws under base. Brass tab swings out from underneath base with instrument specifications (?) Similar to Weston Model #1 with string suspension. Resistance 15.9 Ohms.
Signedon instrument: No L-15875 / CAMBRIDGE / INSTRUMENT CO. LTD. ENGLAND
FunctionReflecting galvanometers are used to measure very small electrical currents and voltage differences. Instead of having a scale with a pointer, in these galvanometers a small mirror turns in the presence of electrical currents. A coil of fine wire hangs between the poles of a magnet that generates a strong magnetic field. When an electric current is sent through the wires of the coil, the coil and the mirror attached to it are deflected. The change of angle can be detected by shining a light at the mirror and observing the reflection on a large scale that is placed in front of the device.
ProvenanceFrom the Engineering School, Harvard University, 1/8/1957.
Leeds & Northrup Company
Date: circa 1920
Object number: 0551
Cambridge Instrument Company, Ltd.
Date: circa 1930
Object number: 1997-1-0106
Cambridge Instrument Company, Ltd.
Date: 1924-1935
Object number: 1989-0031a,b
Emile Gérard & Company
Date: circa 1889
Accessories: coil; case; cover; strings
Object number: 0223a-e
American
Date: 1890-1930
Object number: 0155a,b,c,d
American
Date: circa 1915
Accessories: Extra case of coils and extra set of magnets (0154d). Three extra magnets (3 bar magnets and 2 bar magnets attached to an aluminum wire) are not numbered because of size.
Object number: 0154a,b,c
Leeds & Northrup Company
Date: circa 1910
Object number: 0549
Cambridge Instrument Company, Ltd.
Date: circa 1930
Object number: 0225