The S2-441-SS PAR-FAR sensor is a unique two-channel digital sensor for measuring both the PAR (PPFD) and Far-red outputs of electric grow lights with SDI-12 communication protocol. The sensor features a rugged, aluminum housing that is fully-submersible and built to withstand harsh conditions, and high-quality cable terminating in pre-tinned pigtail leads for easy connection to dataloggers and controllers. The sensor cable includes an IP68 marine-grade stainless-steel cable connector to simplify sensor removal and replacement from permanent installations for maintenance and calibration. Typical applications of PAR-FAR sensors include measuring both the traditional PPFD photosynthetic photon flux and separately quantifying the photon flux of far-red photons (700-750 nm). The outputs include the traditional quantum flux, the far-red photon flux, and the far-red fraction (far-red photon flux density / sum of PPFD and far-red photon flux density). This sensor quantifies far-red photons, and for many applications it reduces the need for a more complex measurement with a spectroradiometer.