A sensor comprising a piezoelectric detector mounted in a support having electrically conductive walls forming a first electrical potential reference, referred to as mechanical ground, to which the piezoelectric detector is connected, and a circuit for processing the signal delivered by the piezoelectric detector, said processing circuit comprising: - an electrical supply circuit defining a second potential reference, referred to as electronic ground, - a charge amplifier comprising an operational amplifier, referred to as a processing amplifier, having: - an inverting input connected to an output of the piezoelectric detector so as to receive the signal delivered by this output of the piezoelectric detector, - a noninverting input connected to the mechanical ground, - an output delivering an output voltage signal referenced with respect to the electronic ground and representative of the signal delivered by the piezoelectric detector, - a capacitive feedback loop between the output and the inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector, said capacitive feedback loop comprising a capacitor of which a first terminal is connected to said inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector, wherein the capacitive feedback loop comprises, between said output of the processing amplifier and said capacitor, a voltage adder circuit (61, 64, 66, 67, 68, 69) adapted to add on the second terminal of said capacitor an electrical voltage which varies as a function of the potential difference between the mechanical ground and the electronic ground, so that the variations of this potential difference are continuously compensated for at the inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector. - an electrical supply circuit defining a second potential reference, referred to as electronic ground, - a charge amplifier comprising an operational amplifier, referred to as a processing amplifier, having: - an inverting input connected to an output of the piezoelectric detector so as to receive the signal delivered by this output of the piezoelectric detector, - a noninverting input connected to the mechanical ground, - an output delivering an output voltage signal referenced with respect to the electronic ground and representative of the signal delivered by the piezoelectric detector, - a capacitive feedback loop between the output and the inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector, said capacitive feedback loop comprising a capacitor of which a first terminal is connected to said inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector, wherein the capacitive feedback loop comprises, between said output of the processing amplifier and said capacitor, a voltage adder circuit (61, 64, 66, 67, 68, 69) adapted to add on the second terminal of said capacitor an electrical voltage which varies as a function of the potential difference between the mechanical ground and the electronic ground, so that the variations of this potential difference are continuously compensated for at the inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector. - an inverting input connected to an output of the piezoelectric detector so as to receive the signal delivered by this output of the piezoelectric detector, - a noninverting input connected to the mechanical ground, - an output delivering an output voltage signal referenced with respect to the electronic ground and representative of the signal delivered by the piezoelectric detector, - a capacitive feedback loop between the output and the inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector, said capacitive feedback loop comprising a capacitor of which a first terminal is connected to said inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector, wherein the capacitive feedback loop comprises, between said output of the processing amplifier and said capacitor, a voltage adder circuit (61, 64, 66, 67, 68, 69) adapted to add on the second terminal of said capacitor an electrical voltage which varies as a function of the potential difference between the mechanical ground and the electronic ground, so that the variations of this potential difference are continuously compensated for at the inverting input of the processing amplifier receiving the signal delivered by the piezoelectric detector.