@@ -16,10 +16,10 @@ Pulse oxygenation devices use several LEDs to measure pulse rate and blood oxyge
- "... 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.
A quick teardown of a ~$20 500BL from Walgreens revealed no integrated photonics package or ASIC; instead, the device uses a bi-color IR/red LED on one side of a spring-loaded plastic clam-shell 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 multi-segment LED device, but the PCB labels suggest an OLED is used for an alternate model. TX/RX test points were spotted that could be investigated further; with any luck, these could be used to pull live data out of the instrument.
