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.
PAR Measurements Characterize Tree Coverages
Using line quantum meter to study the percent of PAR (under canopy/open sky) and its relation to survival and initial growth of native forest species.
Controlling Flowering of Orchids in Greenhouse
Line quantum sensor used to measure PPFD and daily light integral, while experimenting with temperature to control flowering.
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