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.
FOR MORE PRODUCT INFORMATION, CHECK OUT THESE LINKS
• Product Manual
• Specification Sheet
• Technical Drawing
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How is the SQ-500 different from previous Apogee quantum sensors?
The SQ-500 is a full spectrum quantum sensor with a spectral range of 389 to 692 nm ± 5 nm, which can be seen in the graph below. This improved spectral response increases the accuracy of LED measurements.
Where is the SQ-500 used?
The SQ-500 is used to measure incoming PPFD measurements in outdoor environments, greenhouses, growth chambers, and aquariums.
Input Voltage Requirement
5.5 to 24 V DC
1.4 mA (quiescent), 1.8 mA (active)
± 5 %
Less than 1 % (up to 4000 µmol mˉ² sˉ¹)
Non-stability (Long-term Drift)
Less than 2 % per year
Less than 1% (up to 4000 µmol mˉ² sˉ ¹)
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
389 to 692 nm ± 5 nm (wavelengths where response is greater than 50 % of maximum)
Less than 10 % from 412 to 682 nm ± 5 nm
Directional (Cosine) Response
± 2 % at 45 ˚, ± 5 % at 75 ˚
Less than 0.5 %
Less than 0.5 %
-0.11 ± 0.04 % per C
Uncertainty in Daily Total
Less than 5 %
Blue-enhanced silicon photodiode
Anodized aluminum body with acrylic diffuser
-40 to 70 C, 0 to 100 % relative humidity, can be submerged in water up to depths of 30 m
30.5 mm diameter, 37 mm height
Mass (with 5 m of cable)
5 m of two conductor, shielded, twisted-pair wire; additional cable available in multiples of 5 m; santoprene rubber jacket; pigtail lead wires