A system comprising a sensor for detecting a physical variable dependent on an alignment of the sensor about an axis of the sensor, the sensor having a sensor body with a predetermined first form feature that is arranged on an outer face of the sensor body and designed to allow a predetermined alignment of the sensor about the axis, and having a fastening device for the sensor, this fastening device having: a receiving body with a receiving device that is designed to receive the sensor body, and a second form feature that is complementary to the first form feature and arranged on the receiving body, the first form feature having a raised portion on the outer face of the sensor body, and the sensor body having a substantially circular cylindrical form, the alignment of the sensor being a predetermined orientation about a longitudinal axis of the substantially circular cylindrical form, and the raised portion being arranged at a predetermined point on the circumference of the sensor housing, I the system having a fastening means with a third form feature that is complementary to the first form feature and to the second form feature, the receiving device having an elongated opening with a substantially circular cross section, the second form feature having a groove along a longitudinal direction of the opening, and the fastening means having a clamping sleeve that is designed to be received in the opening and to be clamped in it radially between the opening and the sensor body, the clamping sleeve being provided with the third form feature on its circumference, and the third form feature taking the form of an axial slit on the circumference of the clamping sleeve, the sides of these longitudinal slit forming two end portions (12, 13) that are spaced apart, and the two end portions (12, 13) being bent radially outwards, and the groove and the clamping sleeve being designed such that the two end portions (12, 13) project into the groove, and the raised portion of the sensor body of the sensor being arranged between the two end portions (12, 13) that project radially outwards into the groove, a receiving body with a receiving device that is designed to receive the sensor body, and a second form feature that is complementary to the first form feature and arranged on the receiving body, the first form feature having a raised portion on the outer face of the sensor body, and the sensor body having a substantially circular cylindrical form, the alignment of the sensor being a predetermined orientation about a longitudinal axis of the substantially circular cylindrical form, and the raised portion being arranged at a predetermined point on the circumference of the sensor housing, I the system having a fastening means with a third form feature that is complementary to the first form feature and to the second form feature, the receiving device having an elongated opening with a substantially circular cross section, the second form feature having a groove along a longitudinal direction of the opening, and the fastening means having a clamping sleeve that is designed to be received in the opening and to be clamped in it radially between the opening and the sensor body, the clamping sleeve being provided with the third form feature on its circumference, and the third form feature taking the form of an axial slit on the circumference of the clamping sleeve, the sides of these longitudinal slit forming two end portions (12, 13) that are spaced apart, and the two end portions (12, 13) being bent radially outwards, and the groove and the clamping sleeve being designed such that the two end portions (12, 13) project into the groove, and the raised portion of the sensor body of the sensor being arranged between the two end portions (12, 13) that project radially outwards into the groove,