flicker photometer
Date1910-1930
Inventory Number1997-1-1730
ClassificationPhotometer
Subject
Maker
Franz Schmidt & Haensch
1864-present
Supplier
James G. Biddle Company
fl. 1890 - 1950
User
Department of Physics, Harvard University
founded 1884
Cultural Region
Place of Origin
Dimensions34 × 35.8 × 31.2 cm (13 3/8 × 14 1/8 × 12 5/16 in.)
Material
DescriptionThe instrument consists of apertures on each side that let the light sources to be investigated in. These two lights are diffusely reflected within the central chamber by means of white plates and seen through the horizontal eyepiece. The electric motor at the back of the instrument is used to rotate those plates, so that light is reflected alternately from each aperture, thus causing a flicker.
There is a graduated quadrant in front of the motor in order for the photometer to rotate about an axis passing through the horizontal eyepiece. The whole apparatus is supported by a tripod and can be adjusted in height on the central column.
There is a graduated quadrant in front of the motor in order for the photometer to rotate about an axis passing through the horizontal eyepiece. The whole apparatus is supported by a tripod and can be adjusted in height on the central column.
Signedon scale: Franz Schmidt & Haensch. Berlin, S.
on plaque: IMPORTED BY / JAMES G. BIDDLE / PHILADELPHIA
Inscribedon plaque: HARVARD UNIVERSITY 1011
FunctionA flicker photometer is used to compare and determine the difference of luminosity between two light sources. In this instrument, the two light sources are not seen together, as in the standard photometer, but one after the other alternately. The rate of variation is what cause the brightness flicker. When the latter has disappeared and only a uniform hue is seen, it means there is equality of luminance.
ProvenanceThis apparatus came to Harvard's Department of Physics through Ray Sibbs (Division of Engineering and Applied Physics), who believes it was obtained in Arthur Edwin Kennelly's era (1902-1930).
Kollmorgen Corporation
Date: circa 1980
Accessories: Two instructions manuals: SPECTRA PRITCHARD PHOTOMETER, MODEL 1980A, CONDENSED OPERATING INSTRUCTIONS; INSTRUCTION AND MAINTENANCE MANUAL FOR SPECTRA PRITCHARD PHOTOMETER, Model 1980A. Both in gray archival box, C2-H1
Object number: 2004-1-0214a
Adam Hilger Ltd.
Date: circa 1920
Accessories: case, adaptive collars, aperture stops (2): 1/4, 1/6
Object number: 1997-1-1835