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SQ-420 Smart Quantum Sensor | USB Output

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  • Apogee Instruments SQ-420 Smart Quantum Sensor-USB
  • Apogee Instruments SQ-420 Smart Quantum Sensor with included mounting screw.
  • Apogee Instruments SQ-420 Smart Quantum Sensor-Bottom view with included mounting screw. Even with the screw removed, the sensor remains waterproof.
  • Apogee Instruments SQ-420 Smart Quantum Sensor-Back view
  • Apogee Instruments SQ-420 Smart Quantum Sensor-Close up

Product Description

The new SQ-420 smart quantum sensor can be connected directly to a computer 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. 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-420 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-420 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.
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.
No Datalogger Required
The sensor can be connected to a desktop or laptop computer via USB 2.0 type A plug, to be used with the ApogeeConnect software (Windows compatible, XP and later; Mac compatible, 10.10 and later). The included Apogee 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.
Independent Calibration
The SQ-420 is calibrated independently for sunlight and electric light to improve measurement accuracy. The light source calibration can be selected in the settings menu of the Apogee software.


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 % (see Calibration Traceability below)
Measurement Repeatability
Less than 0.5 %
Non-stability (Long-term Drift)
Less than 2 % per year
Less than 1% (up to 4000 µmol m-2 s-1)
Response Time
Software updates every second
Field of View
Spectral Range
410 nm to 655 nm (wavelegnths where response is greater than 50% of maximum; see Spectral Response below)
Spectral Selectivity
Less than 10 % from 469 to 653 nm
Directional (Cosine) Response
± 5 % at 75° zenith angle (see Cosine Response below)
Temperature Response
0.06 ± 0.06 % per C
Operating Environment
-40 to 70 C, 0 to 100% relative humidity; can be submerged in water up to depths of 30 m
24 mm diameter, 28 mm height
Sensor head weighs 90 g
USB Cable
4.6 m (15 ft)
Current Draw
61 mA
4 years against defect in materials and workmanship

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