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

MQ-501: Hand-held Full-spectrum Quantum Meter

The MQ-501 is designed to be an easy-to-use handheld meter for spot-check measurements. The meter includes the AM-001 meter mounting bracket to mount the sensor on a horizontal plane to the meter and approximately 0.17 m of cable to accommodate the bracket length. The full-spectrum sensor incorporates a blue-enhanced silicon photodiode and custom optical filters with a rugged, self-cleaning sensor housing design, anodised aluminium 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.

Compact Handheld Design
The MQ-501 is designed to be an easy-to-use handheld meter for spot-check measurements. The meter includes the AM-001 meter mounting bracket to mount the sensor on a horizontal plane to the meter and shortened cable to accommodate the bracket length.

Refined Spectral Response
Improved spectral response increases the accuracy of LED measurements making it ideal for use with both natural and electric light sources.

Accurate, Stable Measurements
Calibration in controlled laboratory conditions is traceable to an NIST lamp. Quantum sensors are cosine-corrected, with directional errors less than ± 5% at a solar zenith angle of 75°. Long-term non-stability determined from multiple replicate quantum sensors in accelerated aging tests and field conditions is less than 2% per year.

Rugged, Self-cleaning Housing
Patented domed shaped sensor head (diffuser and body) facilitate runoff of dew and rain to keep the sensor clean and minimise errors caused by dust blocking the radiation path. Sensors are housed in rugged anodised aluminium body and electronics are fully potted.

Typical Applications
PPFD measurement over plant canopies in outdoor environments, greenhouses, and growth chambers, and reflected or under-canopy (transmitted) PPFD measurements in the same environments.

Calibration Uncertainty: ± 5%
Measurement Range: 0 to 4000 µmol m-2 s-1
Measurement Repeatability: Less than 0.5%
Long-term Drift (Non-stability): Less than 2% per year
Non-linearity: Less than 1% (up to 4000 µmol m-2 s-1)
Response Time: Less than 1 ms
Field of View: 180°
Spectral Range: 389 to 692 nm ± 5 nm (wavelengths where response is greater than 50% of maximum)
Directional (Cosine) Response: ± 5% at 75° zenith angle
Azimuth Error: Less than 0.5%
Tilt Error: Less than 0.5%
Temperature Response: -0.11 ± 0.03% °C-1
Uncertainty in Daily Total: Less than 5%
Detector: Blue-enhanced silicon photodiode
Housing: Anodised aluminium body with acrylic diffuser
IP Rating: IP68
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 depth of 30 m
Meter Dimensions: 126 mm length, 70 mm width, 24 mm height
Sensor Dimensions: 24 mm diameter, 37 mm height
Mass: 180 g
Cable: Approximately 0.17 m of shielded, twisted-pair wire. Santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions)
Warranty 4 years against defects in materials and workmanship

Calibration Traceability

Apogee Instruments SQ-500 series quantum sensors are calibrated through side-by-side comparison to 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 to the mean of at least three LI-COR model LI-190R 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 that are traceable to the National Institute of Standards and Technology (NIST).