Verfahren zur Bestimmmung der Drehzahl einer Brennkraftmaschine

A method of determining the speed (revs) (n) of a combustion engine (1) which drives a generator (2), in which from a signal (s) produced by the generator a voltage corresponding to a first high-frequency (HF) signal component (s1) and a second low- frequency (LF) signal component (s2) resulting from combustion in the individual cylinders of the engine (1), are ascertained. A proportionality factor (u) is formed from the ratio of the frequencies (f1,f2) of both signal components (s1,s2) and then the revs (n) are determined from the first signal component and the proportionality factor (u). The frequency (f1) of the first high-frequency signal component (s1) is determined by digital high-pass filtering of the signal (s) with subsequent Fourier transformation, and the frequency (f2) of the second low-frequency signal component (s2) is determined by low-pass filtering, with subsequent frequency determination.