tangent galvanometer
Date1880-1900
Inventory Number0320
ClassificationGalvanometer
Subject
Maker
E. Ducretet & Cie
1864 - 1931
Cultural Region
Place of Origin
Dimensions39 × 22 × 19.5 cm (15 3/8 × 8 11/16 × 7 11/16 in.)
Material
Bibliography
DescriptionThe compass has a moving magnet and pointer at an angle, made of aluminum. The compass has a silvered dial and mirror, both found in the bottom of the circular brass dial case. The compass is supported on a brass column. The coil is made of fine wire wound on a brass ring, surrounding the compass case. The base is round, made of brass, and has three legs terminated with leveling screws. The whole base is moveable, on which are found four electrical connectors.
Signedon base, engraved: E. Ducretet & Cie / à Paris
on dial: E. Ducretet & Cie à Paris
Inscribedon column: No. 221
Curatorial RemarksThere is a blue triangle on this instrument, which indicates it was use in the Physics 3 course at Harvard in the late 1920's.
This capillary electrometer, or galvanoscope, is somewhat similar but not exactly identical to the one mentioned in the catalogue cited here.
FunctionAfter the instrument has been leveled, the coil is aligned with the magnetic North-South direction. The compass needle is thus parallel with the vertical plane of the coil. When the current to be measured is sent through the wire forming the coil, it produces a magnetic field of its own, perpendicular to the vertical plane of the coil. This magnetic field displaces the compass needle by a certain angle. Simple vector analysis shows that the current to be measured is proportional the tangent of the angle through which the needle has turned.
The tangent galvanometer is a type of galvanometer introduced in the late 1830s by Claude-Servais-Mathias Pouillet (1790-1868). For the above description and more on tangent galvanometers, see the following website.
The tangent galvanometer is a type of galvanometer introduced in the late 1830s by Claude-Servais-Mathias Pouillet (1790-1868). For the above description and more on tangent galvanometers, see the following website.
ProvenanceFrom the Physics Department, Harvard University.
E. Ducretet & Cie
Date: circa 1879
Accessories: None
Object number: 1999-1-0018