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SQ-520: Full-Spectrum Smart Quantum Sensor (USB)

Make:  Apogee                                   Model:  SQ-520
✅ full-spectrum measurements.
✅ Refined Spectral Response.
✅ No Datalogger Required.
✅ Internal Data Storage.
✅ Measures and combines the intensity of all photons.

FOR SCIENTISTS & SERIOUS GROWERS – Designed by world-renowned crop physiologist, Bruce Bugbee, PhD, the SQ-520 full-spectrum quantum USB sensor is the premium tool of choice among leading scientists and growers for accurately measuring the photosynthetically active radiation (PAR) from all light sources.

QUALITY QUANTUM SENSOR – Unlike cheaper LUX or footcandle sensors which are sometimes marketed as grow light sensors, but are meant for measuring light for human vision, our sensors feature a laboratory-grade PPFD (photosynthetic photon flux density), or “quantum,” optical detector precisely calibrated to measure the light intensity in µmol m-2 s-1 of the specific color wavelengths emitted by LEDs, HPS, MH, sunlight, and other light sources utilized by plants for photosynthesis.

USB COMPATIBLE – Smart quantum sensor can be connected directly to a computer (Windows or macOS X) for taking spot measurements or graphing and datalogging real-time PPFD using the included ApogeeConnect software. The sensor can also act as a stand-alone PAR datalogger by simply connecting it to most standard 5 V DC USB power plugs.

EXTREMELY ACCURATE & STABLE – The sensor precisely measures and combines the intensity of all photons between 400 and 700 nm to give a single PAR reading in µmol m-2 s-1 within 5 % uncertainty. Unlike hobby-grade PAR sensors, our sensor has a stable, accurate calibration with an accuracy drift rate of less than 2 % per year.

RUGGED & EASY TO USE – Quantum sensor head is machined aluminum and potted solid with epoxy for years of use in harsh environments, including underwater. Internal memory within the sensor head is capable of storing 10,000 user-specified periodic measurements that can be downloaded as a CSV file to a computer for analysis. For full-spectrum measurements with both a meter and a sensor, please see our MQ-500.

MADE IN THE USA – All sensors are designed, built, and calibrated at our headquarters in Logan, Utah, USA. Apogee Instruments has been creating research-grade instruments for scientists and serious growers for over 25 years. All sensors are backed by our industry leading four-year warranty and supported by our world-class, US-based customer support team.






General Specification



Sensor head weighs 90 g


24 mm diameter, 37 mm height

Measurement Range

0 to 4000 µmol m-2 s-1

Operating Temperature

-40 to 70 C, 0 to 100 % relative humidity, can be submerged in water up to depths o f30 m

Temperature Response

-0.11± 0.04 % per C

Cable Length

4.5 m (15 ft)

Field Of View


Protection Level