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, and high-quality cable terminating in pre-tinned pigtail leads for easy connection to dataloggers and controllers. 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.
 

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.

Specifications

• Input Voltage Requirement: 5.5 to 24 V DC
• Current Draw: 1.4 mA (quiescent), 1.8 mA (active)
• Calibration Uncertainty: ± 5 %
• Measurement Repeatability: Less than 1 % (up to 4000 µmol mˉ² sˉ¹)
• Non-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: 30.5 mm diameter, 37 mm height
• Mass (with 5 m of cable): 140 g
• Cable: 5 m of two conductor, shielded, twisted-pair wire; additional cable available in multiples of 5 m; TPR jacket; pigtail lead wires; stainless steel (316), M8 connector
• Warranty: 4 years against defects in materials and workmanship
• Manufactured: Made in the USA