During the germination and growth of plant seeds, changes in the ratio of red light to far red light can lead to changes in spectral quality, thereby affecting the photosensitizing pigment Pr/Pfr status of plants. This has a direct impact on the photomorphogenesis of plants, which in turn affects their plant height, leaf diffusion rate, and other photobiological and botanical morphological responses.

The S2-131-SS red/far red light sensor adopts a dual channel design, which simultaneously measures red light (645nm~665nm) and far red light (720nm~740nm) and calculates their ratio (Red/Far red ratio, RFR), that is, the ratio of red light quantum flux density to far red light quantum flux density, to monitor the light environment of plant growth and improve the economy and efficiency of crop planting.

The sensor is a self powered 0-33mV analog output, equipped with an M8 aviation plug, which simplifies the disassembly and replacement of the sensor, facilitates maintenance and recalibration, and can also be directly connected to the AT-100 wireless Bluetooth data logger for use.