Research On The Method Of Acquisition And Processing For BCG Signal Based On SCM

The contraction and pumping blood of human heart can cause the vibration of the human body. The vibration leads to the change of the pressure imposed on the surface of supports that closely contact with human body. We can get the ballistocardiogram(BCG)by recording the pressure change. The effective collection and processing of the BCG signal are always the research hotspots in the field of medical and health. At present,there are many kinds of sensors, such as electrode patch sensors and piezoelectric ceramic sensors, which can be used for collecting human physiological signals.However, the popularization of these sensors is limited in some degree due to high cost and low comfort index. The low-cost fluoride polyvinylidene(PVDF) is used as a sensor in this work. PVDF is made of new polymer materials and has a strong piezoelectric sensitivity. In addition, the advantages, including low cost, simple structure, high safety, no pollution and high sensitivity, make PVDF suitable for applications of non-contact measuring the weak physiological signal. Based on this kind of piezoelectric film, we design a system to collect and process the human physiological signals.We have designed the hardware circuit to collect human body's physiological signals. The circuit consists of the preamplifier circuit, the filter circuit, the voltage amplifier circuit, the notch circuit, the voltage boost and regulator circuit. The preamplifier circuit mainly transforms the electric charge into the voltage. The filter circuit is mainly used for filtering out high frequency noise and direct current interference. The filter is in the range of 0.15-30 Hz. The amplification factor of the voltage amplifier is 100 times. Notch circuit is mainly utilized to remove the power frequency interference. Voltage boost and regulator circuit mainly make the signal meet the requirements of the analog to digital converter(ADC) input. Through the hardware acquisition circuit, we can get a weak physiological signal(BCG signal) with the human body under the state of sitting or lying.The algorithm for extracting the heart rate and respiration rate from the collected BCG signal has been studied in our work. The low pass filter with a cutoff frequency for0.48 Hz is used for the separation of heart rate wave and respiratory wave. The method of successive filtering for three times is adopted in the filter. The extraction of heart rate and breathing rate is determined by fast Fourier transform in frequency domain.The signal processing and result display have been realized by STM32. The displayed results include the heart rate and respiration rate.Our research shows that the design of the acquisition and processing system for the human physiological signal(BCG signal), based on e Touch piezoelectric thin film, isfeasible. At the same time, this system has many advantages, such as safety and convenience, high sensitivity, low price and high reliability.