The S2-131-SS Red - Far-red sensor is a two-channel self-powered sensor. 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 include measuring the Red / Far-red ratio (RFR) for ecological applications, including the effect of spectral quality on phytochrome. The RF ratio influences plant height, leaf expansion rates, and other photobiology and plant morphogenic responses.