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SQ-521-SS SDI-12 Digital Output Full-spectrum Quantum Sensor

Updated:2025-03-13

Brand: Apogee
Model: SQ-521-SS
Description: 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
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Product Details

Overview of SQ-521-SS SDI-12 Digital Output Full-spectrum Quantum Sensor

User 's Manual

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.

SQ-521-SS drawing:

SQ-521-SS specification:

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