Method and device for protecting a turbo-supercharger

Device for determining the characteristic line field for controlling a charged I.C. engine (5), especially for the thermal protection of an exhaust gas turbocharger, comprises an optical window arranged in a housing on the turbine side of the turbocharger driven by an exhaust gas stream (2) of the engine. The blade wheels of the turbocharger and a calibrating surface (8) are located in the visible region of a thermographic camera (3) arranged outside the turbocharger for receiving an image sequence of the measuring surface of the blade wheels. The thermographic camera is connected to an evaluation unit (6), a calibration unit (9), a further evaluation unit (10), a data storage unit (11), and engine control unit (7), a gear control unit (12) and an operating parameter inputting unit (13). An independent claim is also included for a method for determining a characteristic line field for controlling a charged I.C. engine.