The SIF-121-SS is a fast response model infrared radiometer with a 0.2 second response time. The analog sensor is un-amplified and has a voltage output and high-quality cable terminating in pre-tinned pigtail leads for easy connection to dataloggers and controllers. The sensor has a 18° half-angle field of view. Typical applications include plant canopy temperature measurement for use in plant water status estimation, phenotyping, phenomics, 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 SIF-121-SS is designed to be mounted with an Apogee AM-250 commercial-grade mounting bracket.