The SQ-421 is a digital sensor that uses SDI-12 communication protocol. The sensor is calibrated for sunlight and electric lights, selectable through SDI-12 commands, and has a command that automatically applies the immersion effect correction factor for underwater measurements. The sensor features a rugged, self-cleaning sensor housing design. Typical applications include PPFD (Photosynthetic Photon Flux Density) 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 (Photosynthetically Active Radiation)/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 0.5 %
Long-term Drift (Non-stability) 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 chang, fastest data tranmission rate for SDI-12 circuitry is 1 s
Field of View 180˚
Spectral Range 410 to 655 nm ( wavelengths where response is greater than 50 % fo maximum)
Directional (Cosine) Response ± 5 % at 75˚ zenith angle
Temperature Response 0.06 ± 0.06 % per C
Operating Environment -40 to 70 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m
Dimensions 44 mm height, 23.5 mm diameter
Mass 177 g (with 5 m cable)
Cable 5 m of two conductor, shielded, twisted-pair wire, additional cable available in multiples of 5 m; TPR jacket (high water resistance, high UV stability, flexibility in cold conditions); pigtail lead wires
