Apple has opened preorders for the Watch Series 12 and Ultra 4, both featuring a new “Health Sensing System” and S11 chip that Apple says deliver the “most accurate heart rate sensing in a wearable.” The company announced the devices during its fall event today.
The new hardware marks a significant step up in how often the watches check your heart. Apple says the Series 12 and Ultra 4 can take heart rate variability (HRV) measurements up to 24 times more frequently than their predecessors, and they track heart rate every five seconds.
The Health Sensing System
The core of the update is the redesigned sensor array. Apple says the Health Sensing System uses photodiodes organized in a ring to capture light more efficiently, plus a larger electrode surface area for better skin contact. The green LEDs on each watch’s optical heart sensor are bigger and more power-efficient than before.
That design change allows for the higher-frequency readings. Heart rate data now arrives every five seconds, and users can watch it live through a new heart rate watch face complication.
HRV is an indicator of how well the body is able to adapt to changes such as stress and exercise, Apple said.
What Overnight Vitals Adds
Apple is also expanding its Overnight vitals feature. The company said in a press release that Overnight vitals now includes recovery HRV measurements analyzed against a user’s personal baseline, giving a “more complete view of their health status.”
There is also a new daytime vitals view. It lets users toggle between overnight and daytime metrics, and Apple says it “can potentially spot shifts in their metrics before they show up overnight.”
The company did not describe the feature as actively flagging changes in both windows. Its stated purpose is toggling between the two sets of metrics and potentially spotting shifts before they appear overnight.
The S11 Chip
Both watches run on the new S11 chip. Apple did not give detailed performance specs in the announcement, but the chip is what powers the higher-frequency sensing and the new watch face features.
The company did not disclose battery life figures for either model.
Preorders are live now. Apple did not state a shipping date in the announcement.
Series 12 vs. Ultra 4
The two watches share the same sensing technology. Apple did not provide full spec sheets in the announcement, so screen sizes, case materials and exact pricing were not detailed in the source material. What is clear is that the sensing upgrades are identical across both lines.
| Feature | Watch Series 12 | Watch Ultra 4 |
|---|---|---|
| Health Sensing System | Yes | Yes |
| S11 chip | Yes | Yes |
| Heart rate measurement | Every 5 seconds | Every 5 seconds |
| HRV frequency | Up to 24x more than predecessors | Up to 24x more than predecessors |
| Overnight vitals with recovery HRV | Yes | Yes |
| Daytime vitals view | Yes | Yes |
What This Means for Buyers
The headline feature is frequency. Measuring HRV up to 24 times more often than older models is a real jump, not a cosmetic tweak. For people who track recovery, stress or training load, that data density matters.
The daytime vitals view is the other notable addition. Shifting attention to daytime metrics could help catch illness or overtraining earlier, though Apple framed it as a potential signal, not a diagnosis.
The watches are available for preorder now. Apple’s claim of “most accurate heart rate sensing in a wearable” is a strong one, but independent testing will be the real judge of that.
For now, the Series 12 and Ultra 4 are the new flagships in Apple’s wearable lineup. Whether the added readings change how people manage their health is the question that will play out after they ship.
Source: arstechnica.com
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