The Blood Oxygen Saturation Detection Technology Research

The objective of this thesis is to design and investigate a noninvasive measurement of saturated oxygen concentration in human blood. On the basis of consulting a large number of literature, the theory of the oxygen saturation detecting is introduced, the calculation formula of the oxygen saturation is derived, the principle of selecting the light source wavelength is discussed, the theoretical coefficients of the calibration is calculated.A light source driving and controlling circuit, a transimpedance amplifier circuit, a low-pass filter circuit and a microprocessor system circuit are designed, which achieve the automatic adjustment of the light intensity, improve the adaptability of the system to the individual differences of the different people, and convert the changing of the light absorption of the ripple component in the human arterial blood to a voltage signal of pulse wave successfully.On the basis of the signal detected, a DC follow filter, a wavelet transform filter are designed, which filter the pulse DC component, baseline drift and power line interference from pulse wave signal successfully. Based on the pulse rate calculation algorithm and the R-value calculation algorithm, the basis of the oxygen value measuring is determined and the noninvasive detection of oxygen saturation is achieved.The testing software system on the computer which can display the real-time dual pulse wave, set parameter of the measurement, and store the waveform data is designed by using MFC and MYSQL. Six people use the designed pulse oximetry to measure the oxygen saturation. The test results show that the pulse oximetry has met the design requirements and complete the expected functionality.