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

Apogee Extended Quantum (PAR)

The SQ-620 Extended Range PFD sensor is a self-powered sensor.
The SQ-624 Extended Range PFD is an amplified sensor with a 4 to 20 mA output.

Both sensors feature 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 Extended Range PFD 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 Extended Range 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-620 and SQ-624 sensors in indoor grow environments utilizing LED lights.

The analog version of this sensor (SQ-620) 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.


How is the SQ-620 different from previous Apogee quantum sensors?

The SQ-620 is an extended range photon flux density (PFD) sensor with a spectral range of 340 to 1040 nm ± 5 nm, which can be seen in the graph below. The SQ-624 is an extended range photon flux density (PFD) 4 to 20 mA sensor with a spectral range of 340 to 1040 nm ± 5 nm, which can be seen in the graph below.
SQ-620 Spectral Response

Where is the SQ-620 used?

The SQ-620 is used for measuring the newest generation of LED grow lights with wavelengths outside the traditional 400-700 nm PAR range. Research has shown the value of adding UV and far-red LEDs to fixtures to achieve various disease control and photomorphogenic effects. The extended range filter of the SQ-620 & SQ-624 allows it to measure photons from UV and Far-red. The 1040 nm top cutoff also means the sensor will measure spikes in HID and other broad spectrum lights above the range that influences plants therefore the sensor is only intended for use in LED grow environments.



Predicting Stem Elongation and Leaf Expansion: Percent far-red is a better predictor than PPE
If you can’t access the video via Youtube, click here.


Far-red: The Forgotten Photons
If you can’t access the video via Youtube, click here.


Turning Photons Into Food
If you can’t access the video via Youtube, click here.


Toward an Optimal Spectral Quality for Plant Growth and Development
If you can’t access the video via Youtube, click here.


PAR, PPF, PPFD, and PFD Explained


Photobiology Simplified with Dr Bruce Bugbee
If you can’t access the video via Youtube, click here.


Power Supply Self-powered 12 to 24 V DC Current Draw Maximum of 20 mA
Sensitivity 0.05 mV per µmol mˉ² sˉ¹ 0.004 mA per µmol mˉ² sˉ¹
Calibration Factor 20 µmol mˉ² sˉ¹ per mV
Calibration Uncertainty ± 5 %
Measurement Range 0 to 4000 µmol mˉ² sˉ¹
Measurement Repeatability Less than 0.5 %
Output Range (Calibrated) 0 to 200 mV 4 to 20 mA
Long-term Drift (Non-stability) Less than 2 % per year
Non-linearity Less than 1 % (up to 4000 µmol mˉ² sˉ¹)
Response Time Less than 1 ms
Field of View 180˚
Spectral Range 340 to 1040 nm ± 5 nm (wavelengths where response is greater than 50 % of maximum)
Directional (Cosine) Response ± 2 % at 45˚; ± 5 % at 75˚ zenith angle ± 2 % at 45°; ± 5 % at 75°
Azimuth Error Less than 0.5 %
Tilt Error Less than 0.5 %
Temperature Response -0.11 ± 0.04 % per C
Uncertainty in Daily Total Less than 5 %
Housing Anodized aluminum body with acrylic diffuser
IP Rating IP68
Operating Environment -40 to 70 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m
Dimensions 30.5 mm diameter, 37 mm height
Mass 51 g (with 5 m of cable) 140 g
Cable 5 m of two conductor, shielded, twisted-pair wire; TPR jacket; pigtail lead wires; stainless steel (316), M8 connector
Cable Connector M8 M8 connector located 25 cm from sensor head
Warranty 4 years against defects in materials and workmanship