The PPG Physiological Signal for Heart Rate Variability Analysis

The photoplethysmography (PPG) sensor can be applied to measure the situation and function of human blood circulation. The PPG sensor is not only existed the characteristics of simple, convenient and low price but also easy non-invasive to measure physiological signal. The advantage of PPG signal is easy to measure from various sensing location. The physiological information of the clinical detection method is broadly implemented for such type. In this paper, we utilize “the green LED reflective” PPG sensor to capture physiological signals operated in static and exercise modes. Therefore, we adopted the short-term measurement in 5 min. Those captured signals are divided into five segments and 1 min for each segment. We calculated heart beats per minute and heart rate variability (HRV) operated in time domain analysis criteria. The related theory of short-time Fourier transform (STFT) combined with power spectral density (PSD) is implemented for finding HRV in frequency domain analysis. Then, we derived random process theory and the autocorrelation function which are verified the PPG measurement is stationary process or not. In the future experiment, we can compare the 24 h data with the previous results. Consequently, we apply the physical health status monitoring of long-term and short-term modes to observe subject varies of HRV and ANS after listening music concurrently.