Both include a new “Health Sensing System” and S11 chip that give the devices the “most accurate heart rate sensing in a wearable,” Apple claimed during its fall event. Both watches will use the new S11 chip alongside the new “Health Sensing System,” allowing the watches to deliver higher-frequency heart rate and heart rate variability (HRV) measurements than prior Apple Watches. The Health Sensing System includes redesigned photodiodes organized in a ring to capture light more efficiently and a larger electrode surface area for better skin contact.
Additionally, the green LEDs on each Watch’s optical heart sensor are supposed to be bigger and more power-efficient and measure the user’s heart rate every five seconds. Users will be able to view their heart rate in real time with a new heart rate watch face special feature (also known as a complication). The new watches can take HRV measurements up to 24 times more frequently than their predecessors, Apple said.
HRV is an indicator of how well the body is able to adapt to changes such as stress and exercise. A new daytime vitals view lets users toggle between overnight and daytime metrics, and can potentially spot shifts in their metrics before they show up overnight,” Apple said in a press release.
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