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.

The BC20 has a peak measurement and hold circuit which measures the peak power on the detector and holds it. Therefore when a beam is scanned over the detector, when the beam is on the detector it goes up to a peak which corresponds to the same power the detector would measure if the beam was stationary and therefore the BC20 reads the correct power whether the beam is scanned or not. In order for the BC20 to do this, the beam must be on the detector (of size 10x10mm) for at least ~13µs and therefore this limits the scanning speed on the detector to 30,000 inch/s.

Unless otherwise indicated, Ophir sensors and meters should be recalibrated within 18 months after initial purchase, and then once a year after that.

The BC20 sensor was not intended to be used with the StarLite display. If you use the Nova II or Vega display it will work.