3 ms·
You need two LEDs (one visible, one IR) to measure oxygen level, but only one for pulse.
by pps43 6y ago
You need two LEDs (one visible, one IR) to measure oxygen level, but only one for pulse.
- wlesieutre 6y agoApple has apparently had both since their first watch models, but only uses them for heart rate. https://www.theverge.com/2014/9/9/6126991/apple-watch-four-back-sensors-detect-activity https://www.theverge.com/2014/9/9/6126991/apple-watch-four-b... EDIT: Apple says it uses green LEDs during workouts and IR for background measurements. Maybe it’s for energy reasons? https://support.apple.com/en-us/HT204666 https://support.apple.com/en-us/HT204666