|  |

| |

Enabling better global research outcomes in soil, plant & environmental monitoring.

Apogee S2 Series Red-FAR Red Sensor

The RF ratio influences plant height, leaf expansion rates, and other photobiology and plant morphogenic responses.

The S2 Series Red – Far-Red sensor features a rugged, aluminum housing that is fully-submersible and built to withstand harsh conditions. 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. It is also used for monitoring plant light environments, researching plant morphogenic activity, and photobiology studies.


The S2-431 sensor is a digital sensor with SDI-12 communication protocol.

The S2-432 sensor outputs a digital signal using Modbus RTU protocol over RS-232 and RS-485.


You can use the S2-431 FAR-Red Sensor in a Sensor-Node IoT Package (SNiP)

The SNiP-RFR is a ‘Sensor Node Integrated Package’ for LoRaWAN or CAT-M1 communication of real-time FAR Red light measurements for continuous plant, light and environmental monitoring.

The base SNiP-RFR integrates 1x S-NODE and 1x S2-431 Red – Far-Red sensor to a site’s unique network, communication and power requirements. The S-NODE can support an additional 3 sensors.

Calibration Uncertainty ±5%
Measurement Repeatability less than 1%
Long-term Drift less than 2% per year
Non-linearity Less than 1 % (up to 400 µmol mˉ² sˉ¹) (Red and Far-Red)
Response Time less than 1 m
Field of View 180°
Spectral Range 645 to 665 nm ± 5 nm (Red); 720 to 740 nm ± 5 nm (Far-Red)
Measurement Range 0 to 400 µmol mˉ² sˉ¹ (Red and Far-Red)
Directional (Cosine) Response ± 2 % at 45˚, ± 5 % at 75˚ zenith angle
Temperature Response Less than 0.1 % per C
Operating Environment -40 to 70 C; 0 to 100 % relative humidity
Dimensions 30.5 mm diameter, 36.6 mm height
Mass 51 g
4 years against defects in materials and workmanship