It's +/-3% of the reading from full scale down to 5% of full scale. Below 5% of full scale one should switch to next range down for the best accurate linear results.
Power Meters FAQ's
It works there but accuracy is very poor ~20% so it is not specified below 360nm. The PD300-UV is recommended for these shorter wavelengths.
Ophir's Photodiode PD300 and PD300-1W sensors offer automatic background subtraction so the measurement is not sensitive to room light. With "filter out" (i.e. the external filter removed for low light measurements), 2 separate detector elements are visible. The beam to be measured is incident only on the outer of the 2 detectors, but background light reaches both detectors. The instrument will show the power measured by the outer detector minus that measured by the inner detector.This patented method cancels out 95% - 98% of background light under normal room conditions, even if it is constantly changing.
No. We have carefully designed them that there are no such effects from multiple reflections. This is because we use only absorbing or diffusing type elements.