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Original factory packaging
Service Hotline：
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Instrument Expert
Original factory packaging
Service Hotline：
(+86)010-52867771
Updated:2025-03-13
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User's Manual Technical Drawing
The SI-421 has an SDI-12 digital output and high-quality cable terminating in pre-tinned pigtail leads for easy connection to dataloggers and controllers. The sensor has an 18° half-angle field of view and a response time of 0.1 seconds. Typical applications include plant canopy temperature measurement for use in plant water status estimation, road surface temperature measurement of determination of icing conditions, and terrestrial surface (soil, vegetation, water, snow) temperature measurement in energy balance studies. Sensor includes IP68 marine-grade stainless-steel cable connector 30 cm from head to simplify sensor removal and replacement for maintenance and recalibration. The SI-421-SS is designed to be mounted with an Apogee AM-250 commercial-grade mounting bracket.
SI-421 Drawing
| Input Voltage Requirement | 4.5 to 24 V DC |
| Current Draw | 1.5 mA (quiescent), 2.0 mA (active) |
| Calibration Uncertainty (-30 to 65 C) | 0.2 C, when target and detector temperature are within 20 C |
| Calibration Uncertainty (-40 to 80 C) | 0.5 C, when target and detector temperature are different by more than 20 C |
| Measurement Repeatability | Less than 0.05 C |
| Stability (Long-term Drift) | Less than 2 % change in slope per year when germanium filter is maintained in a clean condition |
| 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 | 18° half-angle |
| Spectral Range) | 8 to 14 μm; atmospheric windown |
| Operating Environment | -50 to 80 C; 0 to 100 % relative humidity (non-condensing) |
| Dimensions | 23 mm diameter, 60 mm length |
| Mass | 190 g (with 5 m of lead wire) |
| Cable | 5 m of four conductor, shielded, twisted-pair wire with TPR jacket (high water resistance, high UV stability, flexibility in cold conditions), aditional cable available |
| Warranty | 4 years against defects in materials and workmanship |
| Manufactured | Made in the USA |
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