Guide to UV Measurement
Electronics
Differences in the electronics between instruments can cause one instrument to reach threshold and start counting UV while another instrument needs a higher irradiance value to reach threshold and count. Once an instrument reaches threshold, it normally counts all UV past that particular point. If the optics and electronics in one instrument are set up with a threshold of 40mW and another instrument has a threshold of 2mW, slight differences can be expected between the two readings, especially when the process speed is very slow and the UV system is of low intensity.
Differences in the electronics of radiometers can result in one instrument counting both areas while a second instrument only counts the area after the 40mW threshold is reached.