|As discussed in an earlier article, 2008 is likely to be remembered as the Year of LED Standards, due to the publication of ANSI C78.377 (chromaticity), LM-79 (luminous flux) and LM-80 (lumen maintenance). This article covers further details on LM-80 as well as looking at various guidelines that call on the new standards. It also looks at the impressive array of standards that are currently in process.
LM-80: Lumen Maintenance
As discussed previously, the LM-80 standard describes the measurement of lumen maintenance of LED light sources including LED packages, modules and arrays (but not luminaires). Prediction of lifetime beyond the testing period is not included in the standard. The sidebar “LM-80 Test Report” shows the required data that must be supplied. These are all observable and measurable quantities, and no prediction or extrapolation is involved. The IESNA committee working on a new method, TM-21 “Lumen Maintenance Prediction,” is addressing the real answer to the question of predicting the lumen maintenance of LED sources. The committee is evaluating a number of models to assess lumen maintenance, but this is far more than just a formula.
This article was published in the May/June 2009 issue of LEDs Magazine.
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