The quantum sensor is designed to measure PAR received on a plane
surface. The indicated sensor response (Figure 4) is selected because it
approximates the photosynthetic response of plants for which data is
available. A silicon photodiode with an enhanced response in the visible
wavelengths is used as the sensor. A visible bandpass interference filter in
combination with colored glass filters is mounted in a cosine corrected
head. Error calculations indicate that under sun-and-sky radiation, and
various natural or artificial light sources found in environmental research,
the relative errors are less than ± 5%.