TY - JFULL AU - Fu-Hsuan Huang and Po-Jung Yuan and Kang-Ping Lin and Hen-Hong Chang and Cheng-Lun Tsai PY - 2011/12/ TI - Analysis of Reflectance Photoplethysmograph Sensors T2 - International Journal of Biomedical and Biological Engineering SP - 621 EP - 625 VL - 5 SN - 1307-6892 UR - https://publications.waset.org/pdf/11506 PU - World Academy of Science, Engineering and Technology NX - Open Science Index 59, 2011 N2 - Photoplethysmography is a simple measurement of the variation in blood volume in tissue. It detects the pulse signal of heart beat as well as the low frequency signal of vasoconstriction and vasodilation. The transmission type measurement is limited to only a few specific positions for example the index finger that have a short path length for light. The reflectance type measurement can be conveniently applied on most parts of the body surface. This study analyzed the factors that determine the quality of reflectance photoplethysmograph signal including the emitter-detector distance, wavelength, light intensity, and optical properties of skin tissue. Light emitting diodes (LEDs) with four different visible wavelengths were used as the light emitters. A phototransistor was used as the light detector. A micro translation stage adjusts the emitter-detector distance from 2 mm to 15 mm. The reflective photoplethysmograph signals were measured on different sites. The optimal emitter-detector distance was chosen to have a large dynamic range for low frequency drifting without signal saturation and a high perfusion index. Among these four wavelengths, a yellowish green (571nm) light with a proper emitter-detection distance of 2mm is the most suitable for obtaining a steady and reliable reflectance photoplethysmograph signal ER -