"Apogee quantum sensors underweight blue light, and as a result, photon flux measurements for blue LEDs will be too low. Also, the quantum sensors overweight red light up to a wavelength of approximately 650 nm, above which they do not measure, and as a result, photon flux measurement for red LEDs will either be too high (if the LED output is all below 650 nm) or too low (if a non-negligible fraction of the LED output is above 650 nm). Our quantum sensors will likely provide a reasonable measurement for white LEDs because they are broadband, and because the sensors are calibrated under CWF lamps. However, because of the diversity of LED lighting systems the precise errors have not been quantified. The current spectral response of our quantum sensor can be viewed on our website (
http://www.apogeeinstruments.com/qua...lresponse.html). We are currently working on better filtering in order to achieve a sharp cutoff at both the 400 and 700 nm wavelengths, but this improvement is still a few months away.
That being said, Apogee quantum sensors can be used to measure the relative output of an LED or bank of LEDs, in order to track variability in output with time or temperature for example. However, quantum sensors should not be used to characterize the absolute output of LEDs (except for the possibility of white LEDs), to compare one LED to another, or to determine photon flux for plant growth for example."