Practical Measurement of LEDs and Lighting

This chapter looks in detail at how to make the sorts of measurements of light emitting diodes (LEDs), accurately and in a repeatable fashion. The cheap and easy way to measure the light output of a system is by using a lux meter. Lux meters are properly used for measuring illuminance. The Illuminating Engineering Society of North America (IESNA) has a standard, IES LM‐79‐2008, specifying that the light output of LED‐based luminaires must be measured inside an integrating sphere at thermal steady state. The other IESNA standard that concerns us is LM‐80‐2008. The intent of this is to standardize LED manufacturer lifetime testing procedures. The Alliance for Solid‐State Illumination Systems and Technologies (ASSIST) has put together a number of recommended test procedures for LED lights, focusing on tests that emulate real‐life operation. Particularly important is "LED Life for General Lighting", which recommends 6000 hours of testing for LED lights.