Abstract: A sensor signal from a sensor which measures vibration of an internal combustion engine is filtered by a filter to provide characteristic frequency components for a normal combustion. When the filter signal remains below a reference value, a fault signal is output to indicate a faulty combustion. The filter may be switchable band-pass filters whose output signals are measured for knocking of the motor or for normal combustion. A programmed control unit evaluates the output signals from the filter within a characteristic time segment.

Abstract: In an angular pulse generator having a movable generator part and a read head, the read head has a primary winding (W1) fed with an alternating voltage of a defined frequency and has a secondary winding (W2) whose induced secondary voltage is modulated by passing teeth and intervening gaps of the generator part. An evaluation unit evaluates the phase difference between the alternating voltage and the secondary voltage and forms a pulse for every passing tooth. A stray flux return line surrounds the primary winding (W1), so that the majority part of the primary flux linked to the primary winding (W1) flows via the stray flux return line for a large gap distance of the generator part.