Experimental Study On Pulse Waveform Acquisition Of Smart Bracelet

At present,the acquisition method of pulse waveform is mainly through two methods,infrared sensor volume method and piezoelectric sensor direct measurement method.Infrared sensor is used to detect the hemoglobin content changes in the blood when heart beat to indirectly measure the pulse curve(waveform),there is no direct relationship with the pulse.Piezoelectric sensor measure the beating of blood vessels on the surface of skin directly.So this method is more accurate,the pulse signal waveform is same with the pressure waveform of the finger in traditional Chinese medicine in principle.Therefore,it has great development potential of the use of Chinese Medicine experience.However,due to the large size of the piezoelectric sensor,the circuit is complex and the reliability is poor.This is a fatal weakness to the size sensitive bracelet.Infrared sensor has the advantages of small size,simple circuit,reliable and so on.So the infrared sensor volume method has been widely used.This paper tries to find out the similarities and differences of the two methods in pulse waveform measurement through the experimental method,so as to provide some reference for the determination of the relevant scheme of intelligent wearable devices.An experimental platform is set up to simulate the flow of human blood.The control circuit of solenoid valve was designed.Using STM32 microcontroller as the core CPU to generate a pulse with the human body pulse frequency of the cycle,control the on-off of the electromagnetic valve,simulate the relaxation and contraction of the human heart,and generate the simulation of the pulse wave.At the same time,the drive and signal processing circuit of two kinds of sensors are designed and implemented.In the process of designing filter and amplifying circuit,the circuit is simulated by using Protel 99 se software.Compared with the performance of a variety of circuit components,select the appropriate signal processing circuit.On the basis of simulation,the welding debugging of the actual circuit is carried out.So for just smart wearable devices that are used to measure heart rate and pulse wave velocity,photoelectric sensor can be used to meet the requirements.After set up the experimental platform,With two kinds of sensors to measure the pulse wave generated by the simulation experiment platform,the waveform,phase difference and velocity data were analyzed.The experimental results show that the infrared photoelectric sensor and piezoelectric sensor to measure the pulse period and pulse wave velocity results are basically the same.There are some differences between the two in the waveform of pulse wave.But for the need to use traditional Chinese medicine pulse experience on the pulse waveform obtained for the analysis of intelligent wearable devices,traditional pulse sensor is more suitable.