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Apparently those green LEDs on the back of an Apple Watch flash very quickly to get samples for heart rate calculations. But how fast do they blink?

What is the sampling frequency for the heart rate monitor on an Apple Watch?

  • I don't think Apple has ever stated what frequency they use for their photoplethysmography. I've only seen references to "hundreds of times per second". There's many scientific pages on the web that discuss the frequencies that can be used. – fsb Dec 27 '17 at 14:38
  • It has to be higher than the fastest heart rate possible though ...and basically more than double to avoid aliasing. – Solar Mike Dec 27 '17 at 18:39
  • Yeah, I think so too. It is interesting that they specifically said when using Apple Pencil, iPad Pro will sample the touch screen signal at 240Hz (second generation, 120Hz for the first generation) but no mention about the Apple Watch heart rate monitor. – jackxujh Dec 28 '17 at 0:37

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