Two deiced Rosemount Total Air Temperature (TAT) sensor housings BW102 are used for temperature measurement. As sensing elements a fast open wire PT100 element and a slow encapsulated PT100 element are placed inside the housings.The principal of operation is the measurement of the temperature dependent resistance of a platinum wire. To avoid errors by the airflow disturbance of the aircraft the Total Air Temperature is measured. Total Air Temperature is the maximum temperature attainable by air when brought to rest adiabatically. The inability of achieving a 100% adiabatic compression results in a recovery correction which has to be applied to the calculation of the Static Air Temperature (SAT) of the undisturbed air from the measured temperature.Since the sensing elements can get wet from hydrometeors it will not give an accurate measurement in cloud or precipitation.
The calibration accuracy for temperature is better than 0.1 K for the sensor element, the uncertainty of the conversion of TAT into static temperature (recovery correction, deicing correction) downgrades this accuracy to about 0.5 K in the final static temperature.Temperature sensors are calibrated by the DLR flight department using sophisticated calibration equipment developed within the division. Each calibration procedure is tracable to the national standard and includes an extensive error analysis.