SAT means static air temperature and is the temperature which you can measure if youre standing still in the surrounding air and measure it there. An airplane-fixed temperature probe can do that only parked on the ground (and in reality not even there, cause most of them are aspirated probes). So the temperature probes in airplanes measure another temperature, the so called total air temperature (TAT). That is basically the temperature at the leading edge. This temperature is higher than the SAT in flight cause its affected by the compression-effects you get when flying, the effect is notable above an airspeed of 180-200kts and/or at high altitudes. You can calculate your SAT from TAT with the mach-number, but i can't give you the formula right now, have to look it up.
The free airtemperature gauge is basically a thermometer just hold in the free airstream, like in most small airplanes (
AFAIK correct me if i'm wrong).
[ 17 October 2001: Message edited by: Denti ]