The SI-121 is an un-amplified analog sensor with a voltage output. The sensor has a 18° half-angle field of view and a response time of 0.6 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 IP67 marine-grade stainless-steel cable connector 30 cm from head to simplify sensor removal and replacement for maintenance and recalibration。
Approximate Sensitivity 40 µV per C
Output from Thermopile Approximately -2.2 mV to 2.2 mV for a temperature difference from -55 to 55 C
Output from Thermistor 0 to 2500 mV (typical, depends on input voltage)
Input Voltage Requirement 2500 mV excitation (typical, other voltages can be used)
Measurement Range -60 to 110 C (uncertainty has been determined for the ranges below)
Calibration Uncertainty (-20 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
Field of View 18˚ half-angle
Spectral Range 8 to 14 µm; atmospheric window
Operating Environment -55 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), additional cable available
Warranty 4 years against defects in materials and workmanship
