Connect with us

LED Measurements

Discussion in 'Lighting' started by TKM, Dec 10, 2006.

Scroll to continue with content
  1. TKM

    TKM Guest

    What's the sense of this group regarding the current accuracy of LED
    measurements? Are we seeing realistic numbers, especially lumen output,
    from the manufacturers, test labs and others? What about the answers that
    come from sites such as: http://led.linear1.org/lumen.wiz (millicandelas to
    lumens) -- lots of caveats listed and it sounds like there's a major problem
    defining LED beam angle.

    I know there is standards development work going on that will likely help,
    but has anyone done testing such as taking intensity data, doing a lumen
    calculation and then putting the LED in an integrating sphere?

    Terry McGowan
     
  2. You've already identified the problem with lumen.wiz. Lumen
    Wiz states that it assumes the intensity values are average
    across the beam while most, or even all, manufacturers give
    peak intensity at the center of the beam. There is no
    reliable way to convert a single intensity value into flux.
    If you have the brightness distribution curve, then you can
    integrate all that data. Good manufacturers give flux in
    lumens.
    I haven't, but folks from Labsphere hang out here and they
    have a nice small sphere designed for measuring LEDs. In
    fact, someone, I think Labsphere, introduced a
    battery-powered, hand-held, LED-size sphere with all the
    electronics in the handle perhaps 2 years ago. Just the
    thing to carry around at Light Fair or an LED meetings to
    test devices on display. I little real data would go a long
    way right now.


    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  3. We'll have to get one of those for PLASA next year Adam. :)
     
  4. See: http://www.labsphere.com/productdetail.aspx?id=474

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  5. The cheaper option might be to glue a ping pong ball on a stick and
    attach it to a multimeter with a bit of coiled telephone lead. Then
    just walk about pointing it at their displays, looking at the meter and
    then drawing your breath in sharply while shaking your head. Just like
    we were walking around feeling the temperature of the sources and...
    and... well basically burning our hands. :)

    I mean, it's a foregone conclusion that they've probably hyped the
    intensities a bit. We could have a batch of "INTENSITY EXAGGERATED"
    stickers to put on their products.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-