Pulse Oximeter Improvement with an ADC-DAC Feedback Loop and a Radial Reflectance Sensor

A Small, High Fidelity Reflectance Pulse Oximeter

“…The fingertip plethysmogram consists of ~600 digital levels from peak to valley and has a signal-to-noise ratio of ~30, both of which are substantial improvements over previous designs. 10 Additionally, obtaining high-quality wrist data from a subject can be difficult, often requiring the application of pressure to the sensor in order to reduce the physical distance between the sensor and the major arteries in the wrist. 7 As illustrated in Figure 5, students were also able to obtain viable plethysmographic data from the temple, forehead, nose, ear lobe, and palm.…”

“…Plug-and-play, reflectance pulse oximeters have been previously designed and utilized by this group for multiple education and research applications. [3][4][5][6][8][9][10] The functional block diagram that forms the basis for the previous designs is illustrated in Figure 1. The light-feedback-based approach 7 in Figure 1 drives the LED excitation sources with ever changing currents with a goal of maintaining a constant level for the amount of light that actually reaches the photodiode detector.…”

“…Finally, the authors express their gratitude to Dr. Dwight Day, KSU Department of Electrical & Computer Engineering, for his feedback regarding the digital circuitry used in this version of the pulse oximeter and for the starter circuitry that he offered for the previous version of the pulse oximeter. 10 Opinions, findings, conclusions, or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.…”

Signal Processing methods for PPG Module to Increase Signal Quality

“…The opposite marked signal is given into the signal chain, which compensates DC signal. In recent studies it has been revealed that this method needs much computing power in real-time applications [4]. Authors of the paper have designed a method, which is simple and needs less computing power.…”