Abstract: A fast response temperature sensing device particularly adapted for use in a rarefied fluid media comprises a body of semiconducting material having a precisely predetermined positive temperature coefficient of resistivity in a selected temperature range. The body has ohmic contact element secured thereto to form a small spreading resistance type of resistor element having precisely predetermined resistance characteristics. Leads are electrically connected to the element for connecting the element in an electrical circuit. The element is encapsulated for shielding the element from the environment in a temperature zone to be monitored; and a vane having greater thermal conductivity than the encapsulating material and having greater heat capacity than the resistor element are secured in heat-transfer relation to the element to extend outside the encapsulating material for rapidly conducting heat to the resistor element from the temperature zone.