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

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  • Apogee Instruments SQ-520 USB Smart Full-spectrum Quantum Sensor
  • Apogee Instruments SQ-520 USB Smart Full-spectrum Quantum Sensor with included mounting screw
  • Apogee Instruments SQ-520 Full-Spectrum Quanum Sensor-Bottom view with included mounting screw. Even with the screw removed, the sensor remains waterproof.
  • Apogee Instruments SQ-520 USB Smart Full-spectrum Quantum Sensor-Back view
  • Apogee Instruments SQ-520 USB Smart Full-spectrum Quantum Sensor-Close up
  • New! Apogee Instruments SQ-520 USB Smart Full-spectrum Quantum Sensor

Product Description

The new SQ-520 full-spectrum, smart quantum sensor can be connected directly to a computer via USB for taking spot measurements or graphing and datalogging real-time PPFD using the included 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. 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.

Specification Sheets
Technical Information
Technical Drawings
Technical Information

The SQ-520 is used to measure incoming and reflected PPFD around plants and other organisms in outdoor environments, greenhouses, growth chambers, and underwater.
  USB Smart Quantum PAR Sensor

The versatile SQ-520 can be used two ways - it can be connected directly to a computer for real-time measurements and data logging using the provided software, or it can be connected to a standard USB power source and act as a stand-alone datalogger capable of storing 10,000 periodic measurements internally that can be downloaded to a computer later for analysis.
Refined Spectral Response
The improved spectral response of the SQ-520 increases the accuracy of LED measurements making it ideal for use with both natural and electric light sources.
Spectral Response
No Datalogger Required
The sensor can be connected to a desktop, laptop, or tablet computer via USB 2.0 type A plug, to be used with the Apogee software (windows compatible, XP and later; Mac compatible, 10.10 and later). The included ApogeeConnect software gives the user control of data logging and calibration settings, provides a real time output display and graph of PPFD measurements and allows the data set to be saved as a csv file.
Internal Data Storage
The sensor has internal data storage capability with the ability to hold up to 10,000 measurements. This allows the sensor to collect data while connected to most stand-alone 5 V DC power supply such as a USB wall adapter.

Software Overview:
SQ-420 Software


0.1 µmol m-2 s-1
Calibration Factor
Custom for each sensor and stored in the firmware
Calibration Uncertainty
± 5 %
Measurement Repeatability
Less than 1 % up to 4000 µmol m-2 s-1
Long-term Drift
Less than 2 % per year
Less than 1 % up to 4000 µmol m-2s-1
Response Time
Software updates every second
Field of View
180 °
Spectral Range
389 to 692 nm ± 5 nm (wavelengths where response is greater than 50 % of maximum)
Spectral Selectivity
Less than 10 % from 412 to 682 nm ± 5 nm
Directional (Cosine) Response
± 2 % at 45 °, ± 5 % at 75 °
Azimuth Error
Less than 0.5 %
Tilt Error
Less than 0.5 %
Temperature Response
-0.11 ± 0.03 % C-1
Uncertainty in Daily Total
Less than 5 %
Blue-enhanced silicon photodiode
Anodized aluminum body with acrylic diffuser
IP Rating
Operating Environment
-40 to 70 C, 0 to 100 % relative humidity, can be submerged to depths of 30 m
24 mm diameter, 37 mm height
USB Cable
4.6 m (15 ft)
Sensor head weighs 90 g
Current Draw
61 mA
4 years against defects in materials and workmanship

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