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

QSO-S PAR Sensor

The model QSO-S PAR Photon Flux sensor measures the Photosynthetic Photon Flux (PPF) in µmol m-² s-¹ from a field of view of 180 degrees. The diffusion disk is composed of characterised pigments for good spectral response.

The sensor is designed for continuous outdoor use, and is completely water proof and submersible. The QSO-S is supported by the LSM1 Light Sensor Meter for PAR Sensors or Decagon’s data loggers Em50 or Em50G.

QSO-S PAR Photon Flux Sensor

Spectral range 400 – 700 nm
Accuracy ± 5%
Resolution 2 µmol m-2 s-1
Field of View Hemispherical, 180°
Measurement Range Linear Range: 0-1000 mV (0-5000 µmol m-2s-1)
Full Sunlight: 400 mV (2000 µmol m-2s-1)
Calibrations and Conversions Sensors are calibrated for outside use. 5.0 µmol m-2 s-1 per mV
Operating Temperature -40 to +60°C
Power None, self powered
Cable Length 5m
Cable connector Types 3.5 mm “stereo” plug
Sensor Dimensions 2.4 cm x 2.75 cm (0.95 in x 1.1 in)
Data Logger Compatibility (not exclusive) Decagon Em50 series, ProCheck, Campbell Scientific
Warranty One year, parts and labour


The sensor should be mounted with the cable pointing toward the nearest magnetic pole. For example: in the Northern Hemisphere, point the cable toward the North Pole. In the Southern Hemisphere, point the cable toward the South Pole.

Common Errors:

The biggest error is often caused by dirt on the lens of the sensor. The domed top is self-cleaning, but measurement accuracy will be improved if the lens is wiped with a clean, soft cloth at frequent intervals. Small changes in the level of the sensor can also cause errors. Make sure that the top of the domed sensor body is kept horizontal. Use the included levelling plate to ensure the sensor level.