Test methods for total luminous flux measurement

The total luminous flux (lumen) of SSL products shall be measure with an integrating sphere system or goniophotometer. The method may be chosen depending on what other measurement quantities (color, intensity distribution) need to be measured, the size of SSL products, and other requirement.

Integrating sphere system

Integrating sphere system is suit for total luminous flux and color measurement of integrated LED lamps and relatively small-size LED luminaires (4π geometry sphere is recommended for all types of SSL products including those emitting light in all direction or only in a forward direction, 2π geometry sphere is acceptable for SSL products emitting light only in forward direction). The integrating sphere system has the advantage of fast measurement and does not require a dark room. Air movement is minimized and temperature within the sphere is no subject to fluctuations potentially present in a temperature-controlled room. It shold be noted that the heat from the SSL product mounted in or on the integrating sphere may accumulate to increase the ambient temperature of the product under test.

Goniophotometer

Goniophotometers provide measurement of luminous intensity distribution as well as total luminous flux. Goniophotometers can be measure total luminous flux of SSL products of relatively large size while they can measure small SSL products as well. A goniophotometer is installed in a dark room, normally temperature controlled, and is not sbject to heat accumulation from a source being measured. Care must be taken, however, for drafts from ventilation that might affect measurement of SSL products that are sensitve to temperature. The ambient temperature must be measured and maintained as specified. Measurements with a goniophotometer are time consuming compared to s sphere photometer.