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Enabling better global research outcomes in soil, plant & environmental monitoring.

SIF-100 Series Fast-Response Infrared Radiometers

The SIF-100 series are fast response infrared radiometers with a 0.2 second response time. The analogue sensor is un-amplified and has a voltage output. 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.

Three different models with different fields of view are available:

SI-111 – 22° half-angle field of view.
SI-121 – 18° half-angle field of view.
SI-1H1 – 13° half-angle field of view in the vertical direction.

Approximate Sensitivity 15 µV per °C
Output from Thermopile Approximately -0.825 to 0.825 mV for a temperature difference from -55 to 55°C
Input Voltage Requirement 2500 mV excitation (typical, other voltages can be used)
Output from Thermistor 0 to 2500 mV (typical, depends on input voltage)
Measurement Range -60 to 110°C *Uncertainty has been determined for the ranges below
Calibration Uncertainty (-20 to 65°C) 0.2°C
Calibration Uncertainty (-40 to 80°C) 0.5°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 clean condition
Response Time 0.2s, time for detector signal to reach 95% following a step change
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 shielded, twisted-pair wire. Additional cable available in multiples of 5 m. Santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions). Pigtail lead wires.
Warranty 4 years against defects in materials and workmanship
Accurate Measurements
Calibrated to a custom black-body cone with a measurement uncertainty of ± 0.2°C from -30 to 65°C when the sensor (detector) temperature is within 20°C of the surface (target) being measured. Radiometers are only sensitive from 8-14 μm (atmospheric window) to minimise the influence of water vapour and CO2 on the measurement.
Rugged Housing
Anodised aluminium body with fully-potted electronics. The radiation shield reduces thermal fluctuations.
Output Options
Analogue and digital output options are available. Analogue versions include un-amplified and amplified voltage outputs. Digital versions include SDI-12 and ModBus communication protocols. Sensors are also available attached to a hand-held meter with digital readout.
Typical Applications
Plant canopy temperature measurement for use in plant water status estimation, road surface temperature measurement for determination of icing conditions, and terrestrial surface (soil, vegetation, water, snow) temperature measurement in energy balance studies
SIF-100 Response
Spectral response of SI series infrared radiometers. Spectral response (green line) is determined by the germanium filter and corresponds closely to the atmospheric window of 8-14 μm, minimising interference from atmospheric absorption/emission bands (blue line) below 8 μm and above 14 μm. Typical terrestrial surfaces have temperatures that yield maximum radiation emission within the atmospheric window, as shown by the blackbody curve for a radiator at 28°C (red line)