A design of noninvasive tester of human arterial oxygen saturation

The testing circuit of body noninvasive arterial oxygen saturation is designed according to the characteristics that the light absorption of arterial blood varies with pulse. The driving circuit of testing source and anti-Rossi circuit of compound signal are controlled by DSP sequence signal, and the sending of the testing signal is synchronous with the separation-receiving signal. The high frequency interference of the stray light is attenuated adopting second-order low pass filter of voltage control source. The constant segment and pulsating quantity is extracted respectively from the compound signals by the anti-Rossi circuit of compound signal, second-order high pass filter and secondary low-pass filter. The reverse phase circuit and AC signal amplifying circuit is used respectively for benefiting AD sampling and raising the testing precision. A way to employ moving average method to eliminate noise of the oxyhemoglobin AC signal is proposed, which has raised the testing accuracy.