The SQ-521 is a digital sensor with SDI-12 communication protocol. The sensor incorporates 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.
Input Voltage Requirement 4.5 to 24 V DC
Current Drain 0.6 mA (quiescent), 1.3 mA (active)
Calibration Uncertainty ± 5 %
Measurement Repeatability Less than 1 % (up to 4000 µmol mˉ² sˉ¹>)
-stability (Long-term Drift) Less than 2 % per year
Non-linearity Less than 1% (up to 4000 µmol mˉ² sˉ ¹)
Response Time 0.6 s, time for detector signal to reach 95 % following a step change, fastest data transmission rate for SDI-12 circuitry is 1 s
Field of View 180 ˚
Spectral Range 389 to 692 nm ± 5 nm (wavelengths where response is greater than 50 % of maximum)
Spectral Selectivity Less than 10 % from 412 to 682 nm ± 5 nm
Directional (Cosine) Response ± 2 % at 45 ˚, ± 5 % at 75 ˚
Azimuth Error Less than 0.5 %
Tilt Error Less than 0.5 %
Temperature Response -0.11 ± 0.04 % per C
Uncertainty in Daily Total Less than 5 %
Detector Blue-enhanced silicon photodiode
Housing Anodized aluminum body with acrylic diffuser
IP Rating IP68
Operating Environment -40 to 70 C, 0 to 100 % relative humidity, can be submerged in water up to depths of 30 m
Dimensions 45 mm height, 23.5 mm diameter
Mass 100 g
Cable 5 m of two conductor, shielded, twisted-pair wire; additional cable available in multiples of 5 m; santoprene rubber jacket; pigtail lead wires
