Apogee SQ-420 Quantum PAR Meter (USB)
Free Gift


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 software. The sensor can also act as a stand-alone PAR datalogger by simply connecting it to any standard 5 V 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 waterproof sensor incorporates a blue-enhanced silicon photodiode and custom optical filters with a rugged, anodized aluminum body with acrylic diffuser. Note: The handheld meter is not waterproof, only the sensor and cable are waterproof. 

Original Sensor 

A lower-cost option that is excellent for all light sources, except most LEDs, where post-measurement correction factors need to be applied to achieve accurate readings. The original quantum sensor has a spectral range of 410 to 655 nm seen in graph to the right. The sensor is available attached to a hand-held meter that provides a digital readout (MQ-210) and in multiple analog outputs to be used with a datalogger or voltmeter.




Spectral Response:


Datalogging Capabilities 

The SQ-420 USB sensor has internal memory capable of storing 10,000 user-specified periodic measurements that can be downloaded to a computer. 


The SQ-420 is used to measure incoming and reflected PPFD around plants and other organisms in outdoor environments, greenhouses, growth chambers, and underwater. 

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: 


Resolution 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 1 % Non-stability (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 410 nm to 655 nm (wavelegnths where response is greater than 50% of maximum; see Spectral Response below) 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 Dimensions 24 mm diameter, 28 mm height Mass Sensor head weighs 90 g USB Cable 4.6 m (15 ft) Current Draw (when Logging) 5.1 mA Warranty 4 years against defect in materials and workmanship