Instrument Expert
Original factory packaging
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Instrument Expert
Original factory packaging
Service Hotline：
(+86)010-52867771
Updated:2025-03-13
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User's Manual
Original Sunlight USB Quantum Sensor Designed by world-renowned crop physiologist, Bruce Bugbee, PhD, the Apogee SQ-420X USB smart quantum sensor features Apogee's older and more economical photodetector that is excellent for measuring photosynthetically active radiation (PAR) accurately under sunlight, metal halide, and high-pressure sodium lights. For measuring other light sources, including LEDs, we recommend using our newer full-spectrum or ePAR sensors.
SCIENTISTS & SERIOUS GROWERS：Unlike cheaper LUX or footcandle sensors which are sometimes marketed as grow light meters, but are meant for measuring light for human vision, our sensors feature a laboratory-grade photosynthetic photon flux density (PPFD) optical detector precisely calibrated to measure the light intensity in μmol m-2 s-1 of the specific color wavelengths emitted by sunlight, MH, and HPS lights that are used 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 ApogeeAMS 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.
ACCURACY & STABLE CALIBRATION：The sensor combines the intensity of all photons between 400 and 700 nm under sunlight, metal halide, and high pressure sodium lights to give a single PAR reading in μmol m-2 s-1 within 5 % uncertainty. Unlike hobby-grade PAR meters that are sometimes accurate out of the box, but then lose their calibration quickly, Apogee meters and sensors have an accurate and stable calibration with an industry-leading 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 products with both a meter and a sensor, please see our other original X, full-spectrum, or ePAR meters.
MADE IN THE USA：All meters 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 meters are backed by our industry leading four-year warranty and supported by our world-class, US-based customer support team.
| Resolution | 0.1 μmol mˉ2 sˉ1 |
| Calibration Factor | Custom for each sensor and stored in the firmware |
| Calibration Uncertainty | ± 5 % |
| Measurement Repeatability | Less than 0.5 % |
| Non-stability (Long-term Drift) | Less than 2 % per year |
| Non-linearity | Less than 1 % (up to 2500 μmol mˉ2 sˉ1) |
| Response Time | Software updates every second |
| Field of View | 180? |
| Spectral Range | 370 nm to 650 nm (wavelegnths where response is greater than 50% of maximum) |
| Directional (Cosine) Response | ± 5 % at 75? zenith angle |
| Temperature Response | -0.04 % per C |
| Operating Environment | 10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m |
| Dimensions | 24 mm diameter, 33 mm height |
| Mass | Sensor head weighs 90 g |
| USB Cable | 4.5 m (15 ft) |
| Current Draw | 61 mA |
| Warranty | 4 years against defect in materials and workmanship |
| Manufactured | Made in the USA |
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