What is an Temperature Sensor?

Total air temperature (also designated TAT) is a term used generally in aviation. In other applications it is called stagnation temperature. Total air temperature is measured by a specially designed temperature probe mounted on the surface of the aircraft. The probe is designed to bring the air to rest relative to the aircraft. As the air is brought to rest kinetic energy is converted to internal energy. The air is compressed and experiences an adiabatic increase in temperature. Therefore total air temperature is higher than the static (or ambient) air temperature.

Total air temperature is an essential input to an air data computer in order to enable computation of static air temperature and hence true airspeed.

Outside air temperature (also designated OAT) or static air temperature (SAT) refers to the temperature of the static air around an aircraft without the effects of airspeed.

Useful References:
Military Specification MIL-P-26292 (USAF)
"Pilot and Static Pressure Systems, Installation and Inspection Of"
NASA Reference Publication 1046
"Measurement of Aircraft Speed and Altitude," Wm. Gracey, May 1980 #N80-24296