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Pulse oximeter

Pulse oximeter. Pulse oximeter. Pulse oximeter. Original patent. Your data. Damn, I want some air. Big deep breaths a nd then hold. Gave up. Photodiode detection. Photodiode: Current is proportional to amount of light hitting the detector. Detection demo. We will do something else….

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Pulse oximeter

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  1. Pulse oximeter

  2. Pulse oximeter

  3. Pulse oximeter • Original patent

  4. Your data Damn, I want some air Big deep breaths and then hold Gave up

  5. Photodiode detection Photodiode: Current is proportional to amount of light hitting the detector

  6. Detection demo

  7. We will do something else…

  8. Hysteretic oscillator

  9. Hysteretic oscillator

  10. LED Driver 2.5 V

  11. Background

  12. Background + red Detector sees the sum of the two curves

  13. Background + red + ir Detector sees the sum of the three curves

  14. Convert driving signal to +/- 1

  15. Multiply +/- 1 and detector Driving * Detector Blue – bg only Red – bg + red LED Black - bg +red + ir

  16. Integrate w.r.t time - background (t)) dt

  17. Integrate w.r.t time - bg +red

  18. Integrate w.r.t time - bg +red+ir

  19. Converges to average difference between red and ir We will keep the running integral by using a low-pass filter

  20. Low-passed result

  21. How do we implement a low pass filter in software?

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