An electrically commuted reversible synchronous motor is activated in a calibration journey using an externally forced rotating field, during which an electrical angle of a rotating field and a mechanical angle of the rotor are measured simultaneously at a reference position by an external sensor. These items are stored associated with one another as a measurement series of value pairs. The electrical angle of the rotating field and the mechanical angle of the rotor are also detected simultaneously after direction reversal of the rotating field. These are stored as a second measurement series of value pairs. The angle difference between the electrical angle and the mechanical angle are calculated from value pairs of both measurement series. The correction value for taking the actual incorrect angle into consideration is calculated from the two angle differences by averaging.