{"id":198,"date":"2014-07-09T15:41:22","date_gmt":"2014-07-09T19:41:22","guid":{"rendered":"https:\/\/designinglight.com\/?p=198"},"modified":"2014-07-09T15:41:22","modified_gmt":"2014-07-09T19:41:22","slug":"new-led-performance-measurements","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=198","title":{"rendered":"New LED Performance Measurements"},"content":{"rendered":"

The Illuminating Engineering Society<\/a> (IES) has published two new documents related to measuring the performance of Light Emitting Diodes (LEDs).\u00a0 The titles, as well as the aspects that are included and excluded, reveal the complexity of LEDs.<\/p>\n

The basic problem is that LEDs typically do not fail the way other lamps do.\u00a0 Instead of a failure that results in the end of light output, LED output fades over time.\u00a0 The result is that at some point, although the LED is still producing light, it is no longer producing enough light for the application so we would say that it has reached the end of its useful life.\u00a0 LEDs have very long lives and relatively short development cycles so it is entirely possible that by the time testing of an LED is complete a newer product has already replaced it.\u00a0 This is compounded by the sensitivity LEDs have to temperature, voltage, and other factors that can mean lab measurements differ greatly from real world measurements.\u00a0 This gives rise to the need for clearly defined testing procedures that reproduce conditions found in typical installations so that designers can rely on the information from the manufacturers.<\/p>\n

The first document is LM-84-14<\/a> IES Approved Method for Measuring Luminous Flux and Color Maintenance of LED Lamps, Light Engines, and Luminaires<\/em>.\u00a0 (In the IES naming system LM stands for lumen maintenance, 84 is the document number, and 14 is the year it was issued or updated.)\u00a0 It describes the procedures to be followed in obtaining luminous flux (light output) and color maintenance measurements under standard operating conditions.\u00a0 However, it does not provide information on sampling, or extrapolation of the data for longer time frames.<\/p>\n

The second document is LM-85-14<\/a> IES Approved Method for Electrical and Photometric Measurements of High Power LEDs<\/em>, which describes the procedures to be followed in performing accurate measurements of light output of white and colored high-power LEDs.\u00a0 The procedures do not cover LED arrays or modules, AC driven LEDs, among other things.<\/p>\n

These two documents join several others that describe the testing and measuring of LEDs. The first is LM-79-08<\/a> Approved Method: Photometric Measurements of Solid State Lighting Products<\/em>, which describes the procedures for testing and reporting of: total flux (light output); color temperature; color rendering index, electrical power characteristics; efficacy (in lumens\/watt).\u00a0 LM-79 requires testing of a complete lighting fixture.\u00a0 It does not apply to bare LED packages. LM-79 does not measure the distribution, only the total light output.\u00a0 As a result, it does not provide us with complete photometric performance of the fixture tested.<\/p>\n

The next standard is LM-80-08<\/a> Approved Method:\u00a0 Measuring Lumen Maintenance of LED Light Sources<\/em>, which is intended to measure only the LED package, not a complete fixture.\u00a0 LM-80 does not define the end of life for an LED package.\u00a0 It is simply \u00a0method for determining the light output degradation.\u00a0 LM-80 outlines the testing conditions and the measurement methods that are to be used to measure, track and report the lumen maintenance of an LED package over the course of 6,000 hours.\u00a0 it does not provide a means of estimating life expectancy or light output beyond 6,000 hours.<\/p>\n

TM-21-11<\/a> Projecting Long Term Lumen Maintenance of LED Light Sources<\/em> picks up where LM-80 leaves off. (TM stands for Technical Memorandum)\u00a0 It recommends a method for projecting the lumen maintenance of LEDs using the data obtained from LM-80 testing.\u00a0 TM-21 is used to derive L70, which is the number of hours, or life, before the LED package is emitting 70% of the initial lumens.\u00a0 L70 is the number most frequently used by manufacturers as the life, or the useful life, of their LEDs.<\/p>\n","protected":false},"excerpt":{"rendered":"

The Illuminating Engineering Society (IES) has published two new documents related to measuring the performance of Light Emitting Diodes (LEDs).\u00a0 The titles, as well as the aspects that are included and excluded, reveal the complexity of LEDs. The basic problem is that LEDs typically do not fail the way other lamps do.\u00a0 Instead of a … Continue reading New LED Performance Measurements<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[11],"tags":[30],"class_list":["post-198","post","type-post","status-publish","format-standard","hentry","category-leds","tag-led"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-3c","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":676,"url":"https:\/\/designinglight.com\/?p=676","url_meta":{"origin":198,"position":0},"title":"How Bright Are Colored LEDs?","author":"Jason Livingston","date":"January 29, 2017","format":false,"excerpt":"Measuring and describing the brightness of colored LEDs is an increasingly important part of a lighting designer\u2019s practice. They are used more often, and in more types of projects, than ever before. 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