The Analysis of the Photoplethysmography Signal Characteristic

• Main Authors: Ting-YuKuo, 郭庭瑀
• Other Authors: Jung-Hua Chou
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/75658534438529179755

碩士 === 國立成功大學 === 工程科學系 === 104 === This thesis serves to find the characteristics of light sensors for PPG sensing. Though the light sensors are convenient to employ, the quality of the PPG signal is usually affected by noises and motion artifacts. Therefore, it is essential to know the PPG signal features under different conditions. The PPG signal can be obtained by light sensors of different wavelengths; this study uses three kinds of LEDs to implement for examination, including green (525 nm), red (660 nm), infrared (950 nm) lights. The penetration depth varies with respect to wavelengths, the distribution of blood vessels and capillaries is different for each measurement site. Moreover, different skin colors have distinct absorption of light wavelengths. Experiments are designed to examine the relationship between light wavelengths and measurement sites. Heart rate information is deduced by Fourier transform; the frequency of the highest peak indicates the subject’s heart rate. The experimental results show that the infrared light emitting diode provides the strongest signal magnitude among all measurement sites. The subject who has deep color skin causes reduction on the signal magnitude. The changes of the highest peak position is visible before and after physical exercise. Furthermore, the motion artifact can be evidently observed in the frequency domain. The magnitude decreases after exercise for each subject.