3 ms·

The Series 9 has a better low-power background accelerometer than the Series 8, which is likely the reason.

• Weryj 2y ago
  But, both devices have breathing rate detection during sleep. So it's active in both devices over-night.
  • ezfe 2y ago
    Right, but I assume the "breathing rate" system kicks on much less frequently and precisely than what is needed to be clinically accurate.
    • MBCook 2y ago
      Or perhaps the system in the 9 is more accurate/detailed in preparation for this feature.