The LPPAR01 probe measures the ratio between the number of photons that strike a surface in one second, in the 400 nm…700 nm spectral range and the surface area (m2). 

This quantity is defined as PAR: Photosynthetically Active Radiation.

The probe calibration is carried out by using an halogen lamp, with a known spectral irradiance in a specific spectral range. 

Temperature slightly affects the probe spectral response.

The diffuser and the probe particular structure, allow the response to the variation of the light incidence angle on the diffuser, to be cosine corrected.