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SQ-640-SS Quantum Light Pollution Sensor

Make:  Apogee                                       Model:  SQ-640
✅ Incoming PFD measurements over plant canopies.
✅ Measuring extremely dim light.
✅ Multiple output option.
✅ Cosine-corrected with directional errors.
✅ Long-term non-stability less than 2 % per year.
✅ It is a self-powered sensor.

The SQ-640 Quantum Light Pollution sensor is a 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 of Quantum Light Pollution sensors include incoming PFD measurements over plant canopies in indoor greenhouses or in growth chambers, and reflected or under-canopy (transmitted) PFD measurements in the same environments. Since the detector on this particular Quantum Light Pollution sensor is sensitive to radiation with wavelengths up to 1100 nm, beyond the range of wavelengths that influence plants, we recommend only using the SQ-640 sensors in indoor grow environments utilizing LED lights.

The analog version of this sensor (SQ-640) comes with the inline cable connector placed 30 cm from the sensor head for either standard use as a long-cable pigtail sensor, or for use with our microCache Bluetooth Micro Logger by unscrewing the connector, discarding the long section of cable and then screwing the sensor to the mating connector on the microCache.





General Specification



140 g


30.5 mm diameter, 37 mm height

Measurement Range

0 to 200 µmol m-2 s-1

Operating Temperature

-40 to 70 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m

Temperature Response

-0.11 ± 0.04 % per C

Cable Length

5 m of two conductor, shielded, twisted-pair wire; TPR jacket; pigtail lead wires; stainless steel (316), M8 connector located 25 cm from sensor head

Field Of View


Protection Level



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