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

Smart Quantum Sensor SQ-520

The new SQ-520 smart quantum sensor can be connected directly to a computer 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 any standard 5V DC USB power plug. 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.

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

  • No Datalogger Required.
  • Internal Data Storage – Up to 10,000 measurements.

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.

Resolution 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
Non-Linearity Less than 1% (up to 4000 µmol m-2 s-1)
Response Time Software updates every second.
Field of View 180°
Spectral Range 389 to 692nm ±5nm (wavelengths where response is greater than 50% of maximum)
Spectral Selectivity Less than 10% from 412 to 682nm ±5nm
Directional (Cosine) Response ± 2 at 45 ° zenith angle, ± 5 at 75° zenith angle
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%
Detector Blue-enhanced silicon photodiode
Housing Anodised aluminium 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 30m
Dimensions 24mm diameter, 37mm height
USB Cable 4.6m (15 ft)
Mass Sensor Head: 90g
Power Supply 5V USB power source, 5.1 mA current draw when logging.
Warranty 4 years

SQ-520 Dimensions

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.


Typical Applications

PPFD measurement over plant canopies in outdoor environments, greenhouses and growth chambers, and reflected or under-canopy (transmitted) PPFD measurements in the same environments. Quantum sensors are also used to measure PPFD in aquatic environments, including salt water aquariums where corals are grown.

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. 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.

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 a stand-alone 5V DC power supply such as an independent battery pack or USB wall adapter.

Accurate, Stable Measurements

Calibration in controlled laboratory conditions is traceable to a NIST lamp. Quantum sensors are cosine-corrected, with directional errors less than ±5% at a solar zenith angle of 75°. Long-term non-stability, determined from multiple replicate quantum sensors in accelerated aging tests and field conditions, is less than 2% per year.

Software Overview