@@ -14,3 +14,12 @@ Pulse oxygenation devices use several LEDs to measure pulse rate and blood oxyge
- earlier overview: Yelderman, Mark, and William New. "Evaluation of pulse oximetry." Anesthesiology: The Journal of the American Society of Anesthesiologists 59.4 (1983): 349-351.
- changing LED wavelengths with temp: ~0.1 nm/C: Reynolds, K. J., et al. "Temperature dependence of LED and its theoretical effect on pulse oximetry." British journal of anaesthesia 67.5 (1991): 638-643.
- "... equation (2) is only an approximation and pulse oximeters are usually calibrated empirically using data obtained by inducing hypoxia in healthy volunteers."
## Commercial example
A quick teardown of a ~$20 500BL from Walgreens revealed no integrated photonics package or ASIC; instead, the device had a bi-color IR/red LED on one side and a PCB with a decent sized photodiode on the other, paired with an [SGM8634](www.sg-micro.com/uploads/soft/20190626/1561538475.pdf) op-amp and an STM32F100-series 32-bit Arm Cortex M3 microcontroller. The display is a custom multisegment LED device, but the PCB labels suggest an OLED is used for an alternate model.
