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

Apogee MQ-500 Full Spectrum Quantum Meter

The MQ-500 is Apogee Instruments' new quantum meter with an improved spectral response, providing accurate PAR/PPFD measurements under all light sources, including LEDs.

  • Refined Spectral Response
    The improved spectral response of the MQ-500 increases the accuracy of LED measurements, making it ideal for use with both natural and electric light sources.
  • Rugged Design
    Head is 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.
  • Reliable Accuracy
    To ensure accuracy, each sensor is carefully calibrated in controlled conditions, traceable to NIST reference standards.
Calibration Uncertainty ±5%
Measurement Repeatability less than 1%
Long-term Drift less than 2% per year
Non-linearity less than 1% (up to 2500 µmol m-2s-1
Response Time less than 1ms
Field of View 180°
Spectral Range 389 to 692nm (wavelengths where response is greater than 50% of maximum)
Directional (Cosine) Response ±5% at 75° zenith angle
Temperature Response -0.11 ± 0.03% per °C
Operating Environment 0 to 50°C; less than 90% non-condensing relative humidity up to 30°C;
less than 70% non-condensing relative humidity from 30 to 50°C;
separate sensors can be submerged in water up to depths of 30m
Meter Dimensions 126mm length, 70mm width, 14mm height
Sensor Dimensions 24mm diameter; 35mm height
Mass 100g (with 5m of lead wire)
Cable 2m of shielded, twisted-pair wire; additional cable available; santoprene rubber jacket
Warranty 4 years against defects in materials and workmanship

MQ-500 Dimensions

Mean cosine response of seven Apogee SQ-500 quantum sensors. Cosine response measurements were made on the rooftop of the Apogee building in Logan, UT.

Screen Shot 01-08-16 at 03.05 PM

Cosine response was calculated as the relative difference of SQ-500 quantum sensors form the mean of replicate reference quantum sensors (LI-COR models LI-190 and LI-190R, Kipp and Zonen model PQS 1). The red data are AM measurements; the green data are PM measurements.

Screen Shot 01-12-16 at 09.12 AM

Mean spectral response measurements of six replicate SQ-100 and SQ-500 series quantum sensors. Spectral response measurements were made at 10nm increments across a wavelength range of 300 to 800mm in a monochromator with an attached electric light source. Measured spectral data from each quantum sensor were normalized by the measured spectral response of the monochromator/electric light combination, which was measured with a spectroradiometer


Spectral Errors of Commercial Quantum Sensors

Radiation Source Apogee
Kipp & Zonen
Sun (Clear Sky) -2.2 0.0 -0.4 -1.0
Sun (Cloudy Sky) -1.7 1.4 -0.2 -1.3
Sun (Reflected from Deciduous Leaves) -2.0 4.9 -0.8 1.1
Sun (Transmitted below Wheat Canopy) -1.1 6.4 -0.1 -0.3
Cool White Fluorescent (TS) 0.0 0.0 0.0 0.0
Metal Halide 0.9 -3.7 0.2 -1.7
Ceramic Metal Halide -0.3 -6.0 0.4 -0.7
High Pressure Sodium 0.0 0.8 1.3 1.4
Red/Blue LED (16% 444nm, 84% 667nm peaks) -3.4 – 65.3 3.5 -1.8
Red/White LED (6.5% 436nm, 4.5% 531 nm, 89% 668nm peaks) -3.0 -60.3 2.6 -1.7

Spectral errors are theoretical errors calculated from sensor spectral responses (Apogee SQ-100 and SQ-500 series shown in graph above) and spectral output of radiation sources (measured with a spectroradiometer). Only spectral errors are listed in the table. Calibration, cosine, and temperature error can also contribute to measurement error.

Calibration Traceability

Apogee Instruments SQ-500 series quantum sensors are calibrated through side-by-side comparison the the mean of four Apogee model SQ-500 transfer standard quantum sensors under high output T5 cool white fluorescent lamps. The transfer standard quantum sensors are calibrated through side-by-side comparison the the mean of at least three LI-COR model LI-190 reference quantum sensors under high output T5 cool white fluorescent lamps. The reference quantum sensors are recalibrated on a biannual schedule with a LI-COR model 1800-02 and quartz halogen lamp, traceable to the National Institute of Standards and Technology (NIST).