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

SQ-224 Amplified 4-20 mA Quantum Sensor

The SQ-224 is an amplified sensor with a 4-20 mA output and exhibits excellent cosine response. The sensor was designed for use in environments with significant background electrical noise that can be found in many industrial applications.

  • Rugged Design
    Potted solid sensor head contains no internal air space, and is fully submersible and suitable for use in all climate conditions.
  • Excellent Cosine Response
    Sensors measure PPFD with a cosine response accurate within ±5% at 75° zenith angle.
  • Spectral Error Reduction
    Sensor head features unique blue diffuser to reduce spectral error to less than 5% for sunlight and common electric plant lights, and less than 10% for LEDs.
  • Self-cleaning Head
    The patented dome-shape head quickly sheds water, dirt and other debris, reducing maintenance and maximising performance in the field.
  • Reliable Accuracy
    To ensure accuracy, each sensor is carefully calibrated in controlled conditions and traceable to NIST reference standards.
Power Supply 5-36V DC with a maximum current drain of 22mA (2mA quiescent current drain)
Sensitivity 0.0064 mA per µmol m-2s-1
Calibration Factor 156 µmol m-2s-1 per mA (reciprocal of sensitivity)
Calibration Uncertainty ±5%
Measurement Repeatability < 1%
Non-Stability (Long-term Drift) < 2% per year
Response Time < 1 ms
Field of View 180°
Spectral Range 410nm to 655nm (wavelengths where response is greater than 50% of maximum
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 30m
Dimensions 2.4cm diameter and 2.8cm height
Mass 140g (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
Warranty 4 years

SQ-224 Dimensions

The sensor measures photosynthetically active radiation and is calibrated for use under electric lights. The sensor housing design features a fully potted, domed-shaped head making the sensor fully weatherproof and self-cleaning. 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.

Cosine Response

Screen Shot 01-18-16 at 01.00 PM

Mean cosine response of twenty-three SQ series quantum sensors (error bars represent two standard deviations above and below mean).
Cosine response measurements were made by direct side-by-side comparison to the mean of four reference thermopile pyranometers, with solar zenith angle-dependent factors applied to convert total shortwave radiation to PPFD. Blue points represent the AM response and red points represent the PM response.

Spectral Response

SQ224 graph 2

Mean spectral response of six SQ series quantum sensors (error bars represent two standard deviations above and below mean) compared to PPFD weighting function. Spectral response measurements were made at 10nm increments across a wavelength of 300 to 800nm in a monochromator with an attached electric light source. Measured spectral data from each quantum sensor were normalised by the measured spectral response of the monochromator/electric light combination, which was measured with a spectroradiometer.

Temperature Response

SQ224 graph 3

Mean temperature response of eight SQ series quantum sensors (error bars represent two standard deviations above and below mean). Temperature response measurements were made at 10­°C intervals across a temperature range of approximately -10 to 40°C in a temperature controlled chamber under a fixed, broad spectrum, electric lamp. At each temperature set point, a spectroradiometer was used to measure light intensity from the lamp and all quantum sensors were compared to the spectroradiometer. The spectroradiometer was mounted external to the temperature control chamber and remained at room temperature during the experiment.