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In LED lighting, lumen maintenance is the luminous flux output remaining (expressed as a percentage of the initial output) at any selected elapsed operating time. Lumen maintenance is the converse of lumen method lumen depreciation.〔(【引用サイトリンク】url=http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/XLamp%20Application%20Notes/XLamp_lumen_maintenance.pdf )〕 Lumen maintenance compares the amount of light produced from a light source or from a luminaire when it is brand new to the amount of light output at a specific time in the future. For instance, if a luminaire produced 1,000 lumens of light when it was brand new and now produces 700 lumens of light after 30,000 hours, then it would have lumen maintenance of 70% at 30,000 hours.〔(【引用サイトリンク】url=http://www.philipslumileds.com/technology/lumenmaintenance )〕 Useful lifetime estimates for LED lighting products are typically given in terms of the expected operating hours until light output has diminished to 70% of initial levels (denoted L70 life).〔(【引用サイトリンク】url=http://cool.conservation-us.org/byorg/us-doe/guide_lumen_maintenance.pdf )〕 There are a number of methods for controlling lumen maintenance areas: * Installing photoreceptors tied directly to ballasts, controlling the voltage output to the lamps based on the set level of luminance. * Connecting dimming ballasts directly to an energy management system that has been programmed for the expected depreciation of the lamps; the energy management system directs the output of ballasts as necessary to maintain required lighting levels over time. * Manually verifying lighting levels in a space by using photometers in specific locations, and then manually setting the system to meet lighting requirements.〔(【引用サイトリンク】title=Lumen maintenance )〕 ==LM-80 test== The LM-80 test is a Department of Energy (DOE) approved method for measuring lumen depreciation of solid-state (LED) light sources, arrays and modules.〔(【引用サイトリンク】url=http://clearlightingsolutions.com/pdfs/lm79_80understanding.pdf )〕 The Illumination Engineering Society and the Department of Energy Solid State Lighting Standards Development group worked together to create the LM-80 test criteria. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lumen maintenance」の詳細全文を読む スポンサード リンク
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