calibrated light source

[John Ross Jameson]

Hi,

I've been testing some devices recently that have turned out to behave much
different when a flashlight is shining on them.  I'd like to continue tests
with a calibrated light source (i.e., one whose spectrum and intensity are
known), but I don't have one.  Does anyone have one I could borrow?  I don't
know what wavelength is important, but a white light would seem ideal,
because I don't know what wavelength is affecting the devices.  Also, I'd
like to figure out what wavelength is important, and if you have the 
equipment/experience with doing such experiments, I'd really like to talk
to you.

Thanks,
John