Abstract: It is possible to dispense with a separate ambient pressure sensor. For that purpose, the ambient pressure pu is determined from the absolute pressure ps in the intake tract of an internal combustion engine, the intake air mass flow rate Q and the air temperature T, as well as a pressure loss coefficient Cb. Calibration of the value for the ambient pressure pu determined in this way when the internal combustion engine is idling or at a standstill makes it possible to diagnose an impermissibly contaminated air filter by deducing from the change in the pressure loss coefficient Cb.

Abstract: A configuration for contactless detection of the rpm or speed or of the position of a sensor part includes a differential Hall sensor having a carrier plate with two sides, a permanent magnet disposed on one of the sides, and Hall elements secured on the other of the sides for scanning teeth or segments and gaps of a sensor part of ferromagnetic material being rotatable about an axis or linearly movable in a given direction of motion. According to one embodiment, the carrier plate has an axis of symmetry being perpendicular to the carrier plate and perpendicular to the given direction of motion, and the permanent magnet has a direction of magnetization forming a predetermined magnetization angle with a normal to the given direction of motion.