Research On The Measurement Of Pulse Oxygen Saturation Based On Multiwavelength

Oxygen saturation refers to the percentage of oxygen in the blood and is an important indicator of the oxygen supplying to the body.Utilizing photodetector technology to extract the characteristic information of oxygen saturation from Photoplethysmography signal is the main way of clinical non-invasive to detect the arterial oxygen saturation.At present,dual-wavelength transmission pulse oximetry has become a more mature means of monitoring,but in the case of low oxygen saturation measurement precision is relatively lower,and the transmission range of the sensor is limited.Therefore,in order to overcome these defects,by increasing the wavelength and according to Lambert-Beer derives a mathematical model that is more suitable for a multiwavelength reflective pulse oximeter from a mathematical model of a dual-wavelength transmissive pulse oximeter.Taking into account the measurement accuracy,instrument size and other factors,this article selected four different optical wavelengths,which are 595 nm,735nm,890 nm and805nm reflective blood oxygen sensor to make up for the traditional pulse oximeter Insufficient.First of all,based on the theory of PPG signal optics and physiology,this paper builds a multi-wavelength pulse oximeter acquisition system platform,which mainly demonstrates light source drive circuit,signal acquisition and conditioning circuit,the main control circuit to STM32 microcontroller and power circuits.The PPG signal acquisition,analog / digital conversion,amplification filter,and the converted digital signal sent to the host computer through the serial data analysis and processing;Secondly,in PPG signal preprocessing part,we use sliding average filter,wavelet transform,median filter and LMS-based adaptive filtering algorithm to filter out noise such as high frequency noise,baseline drift and motion artifact in the signal.In addition differential threshold method has been applied to extract PPG signal feature points.Finally,after the completion of the system design and commissioning,pulse oximeter was used to calibrate the instrument,and then compared with the traditional dual-wavelength pulse oximeter,the consequence proves that the design of the system hascertain clinical value.