IES LM-45-00

Describes the procedures and precautions to be observed in the photometry of general service incandescent filament lamps to obtain reliable measurements that can be duplicated in different laboratories performing the same task under substantially the same controlled conditions.

Incandescent filament lamps produce radiation principally in the visible and infrared portion of the electromagnetic spectrum as a result of passing current through a tungsten filament which is surrounded by an inert atmosphere (or a vacuum) and is confined in a glass envelope. The measurements normally made in lamp photometry are luminous flux, luminous intensity, and electrical characteristics. The color temperature and luminance measurements that are sometimes required are not dealt with in this Guide.

This Guide presents a basis for standardizing certain aspects of the electrical and photometric testing of incandescent filament lamps and indicates how these quantities are related to the measurement of luminous flux, luminous intensity, and flux maintenance. Electrical testing consists of measuring current and voltage, with one or the other held constant, and the measurement or calculation of power. Photometric testing consists of measuring the light output (flux or intensity) of individual lamps. Flux measurements allow calculation of efficacy (lumens per watt). Flux maintenance data are obtained by photometry at certain operating time intervals (specified percentages of rated life).