GNGTS 2019 - Atti del 38° Convegno Nazionale

660 GNGTS 2019 S essione 3.2 (Fig. 2b) the frequency response is flattened below the RFr and the amplitude enhanced by an order of magnitude. In this regime the system can work well as seismometer at very low frequencies even though its RFr is high. Fig. 2 - Simulation of the frequency response the ouput voltage with Fast Furier Transform (FFT) of the piezoelectric cantilever under white noise excitation with different magnets distance: a) large distance (linear behavior), b) medium distance (nonlinear frequency softening and c) close distance (highly nonlinear). Experimental results. The preliminary results provided by the simulation and experiment data collection in laboratory suggest the foreseen non-linear behavior of the piezoelectric beam. In particular, the frequency softening shift is due to the nonlinear behavior when magnets are approaching. As a consequence, the frequency operating range above the RFr increases and that below it enhanced in amplitude (Fig. 3). As a result, we can think to exploit this effect for scaling down the size of the sensor. Fig. 3 - Frequency response of piezoelectric device by waring the magnets gap from 9.5 to 4.5 mm. Acknowledgments. This work was financially supported by the Research Project “Implementation of miniature seismometer by non-linear energy (SEISMO-NOLI)”, granted by the “Fondi per la Ricerca di Base 2017” of the Department of Physics and Geology, University of Perugia. We thank Sara Electronic Instruments for their precious suggestions in the project conceptualization and for the supporting the device development. References Bormann, P., Wielandt, E.; 2002. Seismic signals and noise . New manual of seismological observatory practice, Ch 4, 1-62. doi: 10.2312/GFZ.NMSOP-2_ch4