astatic mirror galvanometer
Datecirca 1893
Inventory NumberWJ0056
ClassificationGalvanometer
Subject
Maker
Max Kohl A. G.
founded 1876
Inventor
Leopoldo Nobili
1784 - 1835
Cultural Region
Place of Origin
Dimensions48 × 20 × 21 cm (18 7/8 × 7 7/8 × 8 1/4 in.)
Material
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.
ProvenancePsychology Department, William James Hall, Harvard University.
Historical AttributesThis instrument is found in Hugo Münsterberg's 1893 <i>Psychological Laboratory of Harvard University</i> document. It is thus listed: "216. Galvanometer, with mirror, etc. After Nobili, by Kohl, Chemnitz. $18."
See online reproduction <a href="http://psychclassics.yorku.ca/Munster/Lab/" target="_blank">here</a>.
Harvard Cyclotron Laboratory
Date: 1947-2002
Object number: 2003-1-0291
Daniel Davis, Jr. & E. B. Horn
Date: circa 1850
Object number: 0106
Hindle Instrument Company
Date: circa 1920
Accessories: entire electrocardiograph consists of: bench (RS0372), string galvanometer(RS0372a), time marker (RS0372b), photographic recorder (RS0372f), and several accessories and parts (RS0372c,d,e,g)
Object number: RS0372a
Hindle Instrument Company
Date: 1914-1921
Object number: 1997-1-0312
Buff & Buff Manufacturing Company
Date: circa 1905
Accessories: wood case; leather case; right-angle prism; plumb bob; oil flask; tripod (5174b)
Object number: 5174a
