flicker photometer
Date: 1915-1925
Inventory Number: 1996-1-0614
Classification: Photometer
Subject:
Maker: John Frederick Simmance
Maker: Jacques Abady (1872 - 1964)
Cultural Region:
Place of Origin:
Dimensions:
photometer: 19 × 12.5 × 17 cm (7 1/2 × 4 15/16 × 6 11/16 in.)
case: 22 × 20.5 × 17.5 cm (8 11/16 × 8 1/16 × 6 7/8 in.)
Description:
This photometer is made of a wooden flicker disc box inside of which is a rotating white disc that produces the flicker. (On the side of the box there is a warning in English, French and German that says to not touch the disc.) The box is mounted on a stand, which can itself be mounted on an optical bench rail. There is a graduated quadrant (divided in single degrees) and a pointer that indicates the box's tilt. A knurled tightening screw holds the box in place. On the sides are sighting lenses. One side also has a turn key that rotates the white disc set inside the box. On top, a telescope is used to watch the flicker or, when the intensity of the two lights being observed is identical, the disc appears motionless.
Signedon quadrant: SIMMANCE-ABADY / PATENT
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.
For more on this specific type of photometer, go to the following website.
For more on this specific type of photometer, go to the following website.
Curatorial RemarksThese two inventors were especially involved with gas lighting. See, for instance, their torch for lighting gas lamps 1901 patent, here.
This exact type of photometer was sold by Baird and Tatlock (London) in the 1920s. See the 1924 trade catalogue in the CHSI library (Lib.3555).
This exact type of photometer was sold by Baird and Tatlock (London) in the 1920s. See the 1924 trade catalogue in the CHSI library (Lib.3555).
Primary SourcesJohn Frederick Simmance and Jacques Abady, "The Simmance-Abady "Flicker" Photometer," Proceedings of the Physical Society of London 19 (1903): 39-47.