Measuring average luminosity

Discussion in 'The Projects Forum' started by ErnieM, Aug 24, 2011.

  1. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    I have a project moving to production now that is just a glorified blinkie led where the intensity of a white LED should match an incandescent bulb over a range of 8 to 28 volts. To accomplish this I just control the LED via a switched constant current sink where the PWM of the switch controls the luminous intensity. I'm blinking about at a 200 Hz rate.

    My customer has some expensive photometric instrument he uses to verify this, and I would like to do something similar here on a production basis.

    Is there some meter that can grab the average luminous intensity as a human would perceive it, and give me some sort of output (digital or analog) I can capture? I'm not an optics guy, I know there are nice single chip light to voltage transducers out there, would just passing this output thru a low pass filter be correct?
  2. wayneh


    Sep 9, 2010
    I think that would be close. You will always have the problem of using a different test than your customer. But if your customer will work with you to "calibrate" your test, it should work OK. Just remember it's a proxy, so if anything changes (new LED supplier, eg.), you'll want to check that the calibration still holds. Things like wavelength and spectrum are not controlled in your test, so changes in these could bite you.
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009