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

SQ-310 Series Sun Calibrated Linear PAR Sensors

Apogee line quantum sensors measure a spatial average of photosynthetically active radiation.

The SQ-300 Series

The sensor housing design features an integrated bubble level and is fully potted making the sensor weatherproof. Photosynthetically active radiation (PAR), or photosynthetic photon flux (PPF), is the wavelength range from 400 to 700 nanometers and is strongly correlated with plant growth. Gardeners, greenhouse managers, growth chamber users and salt-water aquarists measure PAR to insure optimal specimen health.

  • The SQ-311 has a sensor bar with 10 internal sensor points and is calibrated for use in sunlight.
  • The SQ-313 has a sensor bar with 3 internal sensor points and is calibrated for use in sunlight.
  • The SQ-316 has a sensor bar with 6 internal sensor points and is calibrated for use in sunlight.


Utilising the SQ-311, SQ-313, or SQ-316 Sensor in a custom IoT (Internet of Things)

The SNiP-SQ3 is a ‘Sensor Node Integrated Package’ for LoRaWAN or CATM-1 communication of real-time photosynthetically active radiation, for continuous plant, light and environmental monitoring.

The base SNiP-SQ3 integrates 1x SQ-313 Sensor with an S-NODE to a site’s unique network, communication and power requirements.

Alternatively, the base SNiP-SQ6 integrates the S-NODE with 1x SQ-316 Sensor; while the base SNiP-SQ10 integrates it with 1x SQ-311 Sensor.

Also available is the SNiP-CLI, which integrates the SQ-311 Sun Calibrated Line PAR Sensor and 1x SQ-110 Sensor with an MFR-NODE to a site’s unique network, communication and power requirements. The MFR-NODE allows for greater data redundancy as it houses an SD card which can retain a copy of the data on site.

Radiation that drives photosynthesis is called photosynthetically active radiation (PAR) and is typically defined as total radiation across a range of 400 to 700 nm. PAR is often expressed as photosynthetic photon flux (PPF): photon flux in units of micromoles per square meter per second (µmol m-2 s-1 , equal to microEinsteins per square meter per second) summed from 400 to 700 nm (total number of photons from 400 to 700 nm). While Einsteins and micromoles are equal (one Einstein = one mole of photons), the Einstein is not an SI unit, so expressing PPF as µmol m-2 s-1 is preferred.

Sensors that measure PPF are often called quantum sensors due to the quantised nature of radiation. A quantum refers to the minimum quantity of radiation, one photon, involved in physical interactions (e.g. absorption by photosynthetic pigments ). In other words, one photon is a single quantum of radiation.

Typical applications of quantum sensors include incoming PPF measurement over plant canopies in outdoor environments or in greenhouses and growth chambers, and reflected or under – canopy (transmitted) PPF measurement in the same environments.

Apogee Instruments SQ series quantum sensors consist of a cast acrylic diffuser (filter), photodiode, and signal processing circuitry mounted in an anodised aluminium housing, and a cable to connect the sensor to a measurement device. Sensors are potted solid with no internal air space, and are designed for continuous PPF measurement in indoor or outdoor environments. SQ series sensors output an analogue voltage that is directly proportional to PPF under sunlight (e.g. model SQ-110) or electric lights (e.g. model SQ-120). The voltage signal from the sensor is directly proportional to radiation incident on a planar surface (does not have to be horizontal), where the radiation emanates from all angles of a hemisphere.

Sensitivity: 0.2 mV per µmol m-2 s-1
Calibration Factor: 5.0 µmol m-2 s-1 per mV (reciprocal of sensitivity)
Calibration Uncertainty: ± 5%
Measurement Repeatability: <1%
Non-stability (Long-term Drift): < 2% per year
Non-linearity: < 1% (up to 2500 µmol m-2 s-1 )
Response Time: < 1 ms
Field of View: 180°
Spectral Range: 410 nm to 655 nm
Directional (Cosine) Response: ± 5% at 75° zenith angle
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: 70 cm length, 1.5 cm width, 1.5 cm height
Mass: 375 g (with 5m of lead wire)
Cable: 5m of shielded, twisted-pair wire. Santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions). Pigtail lead wires
Power Supply: Self Powered
Warranty: 4 years