The Design Of Pulse Sensor Based On PVDF Piezoelectric Film

Piezoelectric sensors have been widely used in modern medical treatment, industrial control, acoustic measurement and structural health monitoring, etc. PVDF piezoelectric film as the emerging piezoelectric material has the advantages of light, soft, fast frequency response, high sensitivity, high strength and mechanical properties, can be used to produce sensors and actuators. Nowadays, the health industry about human people gets more and more attention, the application development of medical equipment in health inspection and maintenance meets the needs of the times.This paper analyzes the common working modes and equivalent circuits of piezoelectric materials, according to piezoelectric equation chooses PVDF piezoelectric membrane under d31 working mode as the core component, further, design a sensor probe which fit the ergonomics to measure human body pulse signal. On this basis, this paper builds a back-end circuit, in order to deal with the pulse of the probe measurements signal. The signal after filter and amplification processing, has clear waveform figure, can be used for doctor's diagnosing reference.Making PVDF piezoelectric sensors to be a curved surface shape can increase its sensitivity, and apply its piezoelectric effect even more significant. Through theoretical analysis, get the relationship between the sensitivity and curvature, and by using ANSYS simulation of piezoelectric effect about PVDF piezoelectric membrane, further verified on the influence of the curvature sensitivity. Through the eddy current displacement measurement of the output voltage of PVDF piezoelectric sensors in different frequency, have a reliable measure frequency interval. Use vibrator produce excitation signal to conduct dynamic test analysis of different frequency of PVDF piezoelectric sensors. Under the condition of the invariable vibrator's input voltage, four kinds of curvature of PVDF piezoelectric sensors have different frequency-voltage curves. The experiment shows, as the vibration frequency continuously increasing, the gap size of curvature in different voltage outputs became apparent. When vibration frequency of external force is bigger, the greater the sensor curvature, the more obvious advantage of sensor's sensitivity is. According to the above conclusion, this paper adopts silicon rubber, PVDF piezoelectric membrane to produce four different curvature PVDF sensors, and use these PVDF sensors to detect the pulse of the human body signal. With different curvature of PVDF sensors for human body measure experiment respectively, gets different pulse signal amplitude, it shows the increase of sensor's curvature really improve sensitivity, but we should consider the actual need to find a moderate value. How to effectively avoid the strength size of press affecting the result of pulse experiment is the next research orientation.