I have created a prototype photo-detector circuit to use in spectroscopy. The micro-controller code take 120 A/D readings and then returns average.
I have noticed that when I use visible light (normal 12v DC lamp), all 120 samples are same (some deviates by +1 and -1). However, using a Deuterium lamp, the samples are sort of rising and falling.
This is the snapshot of the values (Blue when Gain = 0 , Green when Gain = 4) from DC source lamp at 12V DC
This is the snapshot of values from Deuterium lamp (many samples to see the period)
I have noticed that when my Photo-detector circuit is exposed to normal AC light (India standard:230 volt, 50 Hz), then also I see some rising and falling pattern.
*I don't have access or understanding of Deuterium lamp supply.
*I have built a Monochromator to identify and seek to wavelength of my choice which detects the peaks correctly because of averaging.