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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.

The MQ-500 quantum meter is the tool of choice for scientists all over the world to accurately measure photosynthetically active radiation from all light sources. It has a hand-held meter, attached via cable, that displays and stores measurements. The sensor incorporates a blue-enhanced silicon photodiode and custom optical filters with a rugged, self-cleaning sensor housing design, anodized aluminum body with acrylic diffuser. Typical applications include 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 PAR/PPFD in aquatic environments, including salt water aquariums where corals are grown.

The meter has a sample and log mode, and will record an integrated daily total in mol m-2 d-1. Sample mode will record up to 99 manual measurements. Log mode will power the meter on/off to make a measurement every 30 seconds. Every 30 minutes the meter will average the sixty 30 second measurements and record the averaged value to memory. The meter can store up to 99 averages, once full it will start to overwrite the oldest measurement with new ones. An integrated daily total will be recorded from the 48 averaged measurements (making a 24 hr period). Sample and log measurements can be reviewed on the LCD display or by downloading the data to a computer, however, the integrated daily total can only be viewed by downloading the data to a computer. Downloading data to a computer requires the AC-100 communication cable (a standard USB cable will not work) and ApogeeAMS software.

  • 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.

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.

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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).

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