astatic mirror galvanometer
Date: circa 1893
Inventory Number: WJ0056
Classification: Galvanometer
Subject:
Maker: Max Kohl A. G. (founded 1876)
Inventor: Leopoldo Nobili (1784 - 1835)
Cultural Region:
Place of Origin:
Dimensions:
48 × 20 × 21 cm (18 7/8 × 7 7/8 × 8 1/4 in.)
DescriptionThe instrument is supported by a steel tripod, which has three leveling screws. Two coils are fixed on a circular wooden base. Just on top of it is a graduated circle (lines are faded) and a free-moving needle. Attached to the needle is a mirror. From the base rise a curved brass rod, the top end being directly over the needle and mirror. A thread hanging from that rod would have held the astatic system (missing here). Such a system is usually formed by two magnetic needles, in parallel, their poles being put in opposition so they were not influenced by the terrestrial magnetic field.
The current that has to be measured passes between the two coils. This current creates a magnetic field that makes the needle rotate. The rotation is better seen by the rotation of the mirror, which is perceived through the cylindrical tube on the side of the instrument. For small angles, the current intensity is proportional to the rotation of the needle.
A bell jar covers the instrument, limiting external influences.
The current that has to be measured passes between the two coils. This current creates a magnetic field that makes the needle rotate. The rotation is better seen by the rotation of the mirror, which is perceived through the cylindrical tube on the side of the instrument. For small angles, the current intensity is proportional to the rotation of the needle.
A bell jar covers the instrument, limiting external influences.
Signedon plaque: MAX KOHL / Werkstätten für / Präcisionsmechanik / CHEMNITZ I/S
FunctionElectrical apparatus for detecting and determining the intensity and direction of an electrical current.
Historical AttributesThis instrument is found in Hugo Münsterberg's 1893 Psychological Laboratory of Harvard University document. It is thus listed: "216. Galvanometer, with mirror, etc. After Nobili, by Kohl, Chemnitz. $18."
See online reproduction here.
See online reproduction here.
Primary SourcesHugo Münsterberg's 1893 inventory of Harvard's Psychological Laboratory apparatus is located in Harvard University Archives HUF 715.93.72.
ProvenancePsychology Department, William James Hall, Harvard University.