Patent ID: 8418539

Claim:
A method of processing a signal supplied by a piezoelectric sensor, said signal indicating a pressure value, called the cylinder pressure, prevailing in a cylinder chamber of a piston engine such as a heat engine, said signal having a value in the form of pulses separated by components of greater length, called plateaux, corresponding to values of the cylinder pressure which are at least substantially constant, in which method: undesirable variations in the value corresponding to said plateaux of said signal supplied by said sensor are compensated by a compensation circuit comprising a closed-loop servo control which, when it is active, is capable of supplying an output signal with a value set to a predetermined constant value Sr, called the reference value Sr, independently of any undesirable variations in the value corresponding to said plateaux of said signal supplied by said sensor, said signal supplied by said sensor is treated by an operational amplifier, said operational amplifier receiving said signal as an input and supplying said output signal as an output, said closed-loop servo control supplying a compensation current Icorr as an input of said operational amplifier in parallel with said signal supplied by said sensor, wherein: the value of said output signal is measured and stored for successive sampling moments at a sampling frequency greater than the maximum frequency of said pulses, at each sampling moment, a value indicating a variation ΔS in the output signal with respect to a past sampling moment is calculated, at each sampling moment, if the absolute value of said variation ΔS is less than a predetermined comparison value V, said servo control is kept active to set the output signal to said reference value Sr, the value of said output signal being a value corresponding to a plateau.