{"id":2006,"date":"2022-04-26T06:39:43","date_gmt":"2022-04-25T21:39:43","guid":{"rendered":"https:\/\/digitalbikeparts.com\/?p=2006"},"modified":"2022-04-29T21:39:38","modified_gmt":"2022-04-29T12:39:38","slug":"measuring_the_lumens_with_an_integrating_sphere","status":"publish","type":"post","link":"https:\/\/digitalbikeparts.com\/en\/measuring_the_lumens_with_an_integrating_sphere\/","title":{"rendered":"How to measure lumens of a light with an integrating sphere"},"content":{"rendered":"\n<p>It is quite easy to measure the <a href=\"https:\/\/en.wikipedia.org\/wiki\/Illuminance\">illuminance<\/a> of a light at a single point. <br>However, it&#8217;s not easy to measure <a href=\"https:\/\/en.wikipedia.org\/wiki\/Lumen_(unit)\">lumens<\/a>.<br>Lumen is unit for luminous flux. It means total quantity of&nbsp;visible light&nbsp;emitted by a lighting device.<\/p>\n\n\n\n<p>I&#8217;ll show you how I measure lumens of lights below. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">It&#8217;s not easy to measure total quantity of visible light<\/h2>\n\n\n\n<p> It is easy to measure the illuminance of a light at a single pinpoint.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-5.png\" alt=\"\" class=\"wp-image-2047\" width=\"514\" height=\"294\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-5.png 1000w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-5-300x172.png 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-5-150x86.png 150w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-5-768x441.png 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-5-485x278.png 485w\" sizes=\"(max-width: 514px) 100vw, 514px\" \/><\/figure>\n\n\n\n<p>The illuminance of a particular point can be measured easily with an illuminance meter like this one shown below.<br>This is the EM-9300SD measuring instrument I purchased in 2016.<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-rich is-provider-twitter wp-block-embed-twitter\"><div class=\"wp-block-embed__wrapper\">\n<blockquote class=\"twitter-tweet\" data-width=\"550\" data-dnt=\"true\"><p lang=\"ja\" dir=\"ltr\">\u30e9\u30a4\u30c8\u306e\u7167\u5ea6\u8a08\u6e2c\u306e\u305f\u3081\u4e45\u3005\u306b\u53d6\u308a\u51fa\u3057\u305f\u3002\u9577\u62bc\u3057\u3068\u304b\u99c6\u4f7f\u3059\u308b\u306e\u3067\u30de\u30cb\u30e5\u30a2\u30eb\u3092\u898b\u306a\u3044\u3068\u64cd\u4f5c\u65b9\u6cd5\u304c\u7d76\u5bfe\u306b\u308f\u304b\u3089\u306a\u3044\u3002 <a href=\"https:\/\/t.co\/l4CqTFVTLo\">pic.twitter.com\/l4CqTFVTLo<\/a><\/p>&mdash; d@ (@dea_tea_1) <a href=\"https:\/\/twitter.com\/dea_tea_1\/status\/939071932418244608?ref_src=twsrc%5Etfw\">December 8, 2017<\/a><\/blockquote><script async src=\"https:\/\/platform.twitter.com\/widgets.js\" charset=\"utf-8\"><\/script>\n<\/div><\/figure>\n\n\n\n<p> However, a light illuminates a large area rather than a single point.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-6.png\" alt=\"\" class=\"wp-image-2048\" width=\"502\" height=\"288\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-6.png 1000w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-6-300x173.png 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-6-150x86.png 150w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-6-768x442.png 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-6-485x279.png 485w\" sizes=\"(max-width: 502px) 100vw, 502px\" \/><\/figure>\n\n\n\n<p>Now we are measuring the illuminance of two lights.<br>Suppose that their measured illuminance at a center illuminated point are the same.<br>In this case, the light with the larger illuminating area is judged to be brighter overall.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-7.png\" alt=\"\" class=\"wp-image-2049\" width=\"414\" height=\"435\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-7.png 856w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-7-285x300.png 285w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-7-143x150.png 143w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-7-768x807.png 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-7-485x510.png 485w\" sizes=\"(max-width: 414px) 100vw, 414px\" \/><\/figure>\n\n\n\n<p>Then, how should we measure the total quantity of&nbsp;visible light&nbsp;emitted by those lighting devices?<br>One possible method is to place light-measuring sensors in multiple locations.<\/p>\n\n\n\n<p>However, each light can have different illuminated area.<br>Even if the measurement results are obtained at multiple points, it is not easy to determine how to relate them to the total light quantity.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-8.png\" alt=\"\" class=\"wp-image-2050\" width=\"497\" height=\"308\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-8.png 1000w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-8-300x186.png 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-8-150x93.png 150w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-8-768x477.png 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-8-485x301.png 485w\" sizes=\"(max-width: 497px) 100vw, 497px\" \/><\/figure>\n\n\n\n<p>In addition, slight differences in distance and the orientation of the light sensor can significantly change the measured light intensity.<\/p>\n\n\n\n<p><br>Thus, it is difficult to measure the total light quantity with this kind of illuminance meter<\/p>\n\n\n\n<p><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Measuring lumens (total luminous flux) with an integrating sphere<\/h2>\n\n\n\n<p>I use an integrating sphere to measure the total luminous flux (total luminous flux = lumens) of a light.<\/p>\n\n\n\n<p>Integrating sphere is used to measure lumens. When light is illuminated in a sphere, the inside of the sphere is filled with a homogeneous brightness due to the reflection of light within the sphere.<\/p>\n\n\n\n<p>With a sensor in the sphere, the light lumen value can be measured.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-9.png\" alt=\"\" class=\"wp-image-2051\" width=\"442\" height=\"396\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-9.png 884w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-9-300x269.png 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-9-150x134.png 150w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-9-768x688.png 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-9-485x435.png 485w\" sizes=\"(max-width: 442px) 100vw, 442px\" \/><\/figure>\n\n\n\n<p>This is the integrating sphere. It&#8217;s a hollow steel sphere with a diameter of 50 cm (about 1.64 feet).<\/p>\n\n\n\n<figure class=\"wp-block-image size-large is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/ecd53aba-1024x768.jpeg\" alt=\"\" class=\"wp-image-457\" width=\"512\" height=\"384\"\/><\/figure>\n\n\n\n<p>The inner surface of the integrating sphere is coated with highly reflective barium sulfate.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001-1024x768.jpeg\" alt=\"\" class=\"wp-image-458\" width=\"512\" height=\"384\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001-1024x768.jpeg 1024w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001-300x225.jpeg 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001-768x576.jpeg 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001-1536x1152.jpeg 1536w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001-485x364.jpeg 485w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/01\/f584e001.jpeg 1000w\" sizes=\"(max-width: 512px) 100vw, 512px\" \/><\/figure>\n\n\n\n<p>A measuring device called a &#8220;spectral luminous flux analyzer&#8221; is connected to the integrating sphere to measure lumens.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted.jpg\" alt=\"\" class=\"wp-image-1528\" width=\"384\" height=\"512\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted.jpg 750w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-225x300.jpg 225w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-113x150.jpg 113w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-485x647.jpg 485w\" sizes=\"(max-width: 384px) 100vw, 384px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">For Correct Measurement<\/h2>\n\n\n\n<p>Even when using an integrating sphere, changes in measurement conditions can cause deviations in lumen values. <br>To avoid deviations in the measured values, I make several efforts as shown below.<br><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>The mounting position and angle of the light and the measurement device should be constant. (See (Remarks))<\/li><li>The performance of lights and batteries is greatly affected by temperature. Therefore, I keep the room temperature between 20\u2103 (68\u2109) and 25\u2103 (77\u2109).<\/li><li> Use new, I use charged batteries. <br>As a rule, I use lights and batteries that have not been used for cycling.<\/li><li> For alkaline battery-powered lights, I use batteries of the same brand, with a new production date and unused. <br><\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"> (Remarks) Placement of lights on the integrating sphere<\/h2>\n\n\n\n<p><span style=\"font-size: revert; letter-spacing: 0.025em; background-color: var(--inner-content-bg); color: var(--main-text-color);\">According to the instructions attached with the integrating sphere, lights can be placed either &#8220;outside the sphere&#8221; or &#8220;inside the sphere&#8221; as shown in the figure below.<\/span><br>However, in practice, if the light is placed inside the sphere, the exterior of the light itself will absorb light. <br>Therefore, depending on the size and color of the light, the lumen measured will vary.<br>In particular, a lighting device with a black exterior absorbs light itself, resulting in lower measured lumens.<br><\/p>\n\n\n\n<p>When I measure lumens, a lighting device is placed outside the sphere and light is irradiated into the sphere. <br>If the light is placed on the outside, it is necessary to take measures to shield the light. <br>A hole must be prepared to match the shape of the light. In fact, this process is quite time-consuming.<br><br><\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"1000\" height=\"423\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-10.png\" alt=\"\" class=\"wp-image-2052\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-10.png 1000w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-10-300x127.png 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-10-150x63.png 150w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-10-768x325.png 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2022\/04\/image-10-485x205.png 485w\" sizes=\"(max-width: 1000px) 100vw, 1000px\" \/><\/figure>\n\n\n\n<p>The analyzer is calibrated with a reference bulb provided by the measurement device manufacturer. <br>The following is a reference bulb. It has been verified in advance that it emits a certain lumen of light when a specific electric current value is applied, and the analyzer is calibrated with that light.<br><\/p>\n\n\n\n<figure class=\"wp-block-image size-large is-resized\"><img decoding=\"async\" src=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-1024x696.jpg\" alt=\"\" class=\"wp-image-1529\" width=\"512\" height=\"348\" srcset=\"https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-1024x696.jpg 1024w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-300x204.jpg 300w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-150x102.jpg 150w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-768x522.jpg 768w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-1536x1044.jpg 1536w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1-485x330.jpg 485w, https:\/\/digitalbikeparts.com\/wp-content\/uploads\/2021\/11\/Pasted-1.jpg 1000w\" sizes=\"(max-width: 512px) 100vw, 512px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>It is quite easy to measure the illuminance of a light at a single point. However, it&#8217;s not easy to meas&#8230;<\/p>\n","protected":false},"author":2,"featured_media":1091,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"cybocfi_hide_featured_image":"","_locale":"en_US","_original_post":"https:\/\/digitalbikeparts.com\/?page_id=150","footnotes":""},"categories":[78],"tags":[74,73,72],"class_list":{"0":"post-2006","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-lumen-measurement-methods","8":"tag-integrating-sphere","9":"tag-lumen","10":"tag-pickup-en","11":"en-US","12":"article"},"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>How to measure lumens of a light with an integrating sphere - Digital Bike Parts<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/digitalbikeparts.com\/en\/measuring_the_lumens_with_an_integrating_sphere\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How to measure lumens of a light with an integrating sphere - Digital Bike Parts\" \/>\n<meta property=\"og:description\" content=\"It is quite easy to measure the illuminance of a light at a single point. 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