The seismic mass is fixed to the mounting base by a tension bolt. This bolt passes with an important play through an opening of the piezoelectric transducer arranged between the mounting base and the seismic mass. Under the influence of inertial forces which act perpendicularly to the axis of the bolt on the seismic mass, bending loads occur which result in an increase of the pressure at one side and in a decrease of the pressure at the other side of the piezoelectric transducer. The transducer has halves polarized in opposite directions and subjected to pressures varying in opposite sense and electrodes covering the top and bottom surfaces of the halves, signals of the same polarity being induced under the bending loads. External influences which act uniformly on the transducer are compensated.