Shielded probe. A thermistor is a temperature-sensing element composed of sintered semiconductor material which exhibits a large change in resistance proportional to a small change in temperature. Bipolar connector used in the TPI thermistor probe line. Measure air temperatures in duct work. Measure air temperature coming from diffusers while Trouble-shooting heating and air conditioning systems. Measure flame temperatures to trouble-shoot industrial heating applications. Calibrate thermostats using an ambient air probe. 44 Probe tip. 3-19/128" Stem length. 1/8" Diameter. 15-89/128" Lead length. Temperature range: -40 degree to 300 degree F (-40 degree to 150 degree C). PVC Insulation material. RoHS Compliant.