Research PVDF Vibrating Wire Infrasound Sensor

Among the acoustic wave bands, the frequency less than20HZ is called infrasound. Because infrasound has a low frequency and a long wavelength, it has some outstanding characteristics, like far spreading, strong penetrating power, small interference, etc. Infrasound, which human beings can’t hear, plays more and more important roles in our life and scientific research. If we can make a high-precision detection of infrasound and timely forecast in advance of all kinds of natural disasters, lots of unnecessary loss of property and life casualties can be avoided. In order to solve the above problem, this paper designs a vibrating-wire infrasound sensor based on PVDF (Polyvinylidene fluoride), on the basis of the latest research achievements about infrasound sensor in the domestic and international.First, this paper analyses the various principles of infrasound sensors. PVDF infrasound sensor’s principle is using flexible diaphragm to receive infrasound, and transfer it to PVDF membrane, the piezoelectric properties of PVDF converts the frequency for the change in charge, eventually converts the charge into a voltage value output through conversion amplified circuit. The folk instrument huur’s sound principle is that the string’s vibrating conducts to the diaphragm through the nut, then the diaphragm vibrates strongly, strengthen and filter the vibration of the strings, thus expand the volume, and produce rich tone. Using both the structure and principle of the above, the scheme of vibrating-wire infrasound sensor is given.Secondly, this paper uses vibrating-wire as the sensing element of the sensor, receiving infrasound signal directly, then pass the vibration of vibrating-wire to the diaphragm with the bridge as a conduction medium, convert vibration frequency to the change of the charge through the other side of the elastic element of PVDF, eventually get the voltage output through the electric charge amplifier, transform and output, filtering circuit. This paper gives detail instructions of the elastic element material selection, parameter design, and the feature analysis of the diaphragm, besides mathematical model, parameter design and production of PVDF piezoelectric film paste, and sensitive element material selection.At last, test the sensor and make a data analysis, getting some important indicators, including the infrasound sensor’s measured frequency, the measured voltage value, range and error, etc. According to the test results and the problems in the design, some improved method is put forward.