Capturing Physiological Signal by Using Micro Biomedical Device

The Photoplethysmographic (PPG) sensing module uses optical signals to measure pulse rate (PR) and blood oxygen concentration (SPO2). This paper designs a system that can measure human physiological signals, analyze in real time, and display the graph and store the data. Since the use of PPG is very convenient, it is not easy to make mistakes in use. Moreover, the PPG signal is related to the ECG signal, so the use of PPG to replace the traditional ECG device greatly improves convenience and can reduce costs. The signal measured by the PPG module is a time domain signal waveform. After Fourier transform, the original time domain signal can be converted into a frequency domain signal, and the power spectral density (PSD) of the original signal can be obtained. Because the low frequency (LF) and high frequency (HF) components of PSD are related to sympathetic and parasympathetic activity, respectively, and the ratio of LF to HF represents the autonomic nervous system (ANS) parameters. Therefore, by subdividing these parameters, the characteristics of the physiological signal can be captured.