SIMMANCE FLICKER PHOTOMETER CIRCA 1920, circa 1920

A Flicker Photometer is used to compare two sources of light by alternating them with a clockwork disc that reflects them through a viewing tube. One light source is presented to the tube on the left and positioned onto a cross hair at the end of the tube; the same is done for the second light source through the other tube opposite. Both tubes are then lifted revealing the white disc inside. Winding the clockwork motor up and screwing in the speed control on the other side of the box will cause the reflecting disk to rotate; the disc is bevelled once on both sides to 45 degrees but 180 degrees opposite each other, reflecting the light upwards alternately. By viewing the result through the brass tube in the middle, which can be focused by pulling the lens outwards, the flickering light sources can be compared. When both sources are equal irrespective of colour the flickering will reduce. If both lights are of the same colour the disc will appear to become stationary. Uses for this instrument are in Photography and Optometry among many others, before being replaced with electronic equipment.

Donated by David Hall

A1612