Product1 publisher3 min readPublished
Apple's Series 12 logs 17,280 heart rate readings a day where the last one logged 288
The redesigned sensor array and the S11 chip ship now and can be checked against a chest strap. Audio Intelligence and the rest of Apple's health AI arrive later this year, and The Verge's reviewer could not test them.
The Product Desk · Product desk
What happened
- The Series 12 keeps the case, buttons, sizes and sensor types of earlier Apple Watches, and puts this year's changes in a new S11 chip and a completely redesigned health sensor array.
- Resting heart rate sampling moves from once every five minutes to once every five seconds, and the watch now samples at that rate during activity as well.
- Several of the most interesting health and AI features, including the Audio Intelligence ambient listening suite, arrive later this year and were not available for review.
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Why it matters
- decision A buyer this month pays in full for a sensor upgrade a week of wearing can verify and for an inference layer no one outside Apple has used.
- capability Continuous sampling brings the Apple Watch into range for people who need their heart rate watched all day because of a chronic condition.
- constraint "Later this year" is the only timing attached to the features the whole-day pitch rests on, so a rollout built around them has nothing to schedule.
- exposure The person handing over the watch owns the ambient listening conversation, and Apple's own reviewer doubts the privacy design will settle how laypeople feel.
For a person tracking a heart condition, the change that lands on day one is a count. Five-minute resting sampling produced 288 readings a day. Five-second sampling produces 17,280, sixty times as many [5][6]. The array underneath reads the same signals with bigger and rearranged parts: larger EKG electrodes for better skin contact, photodiodes rearranged to catch reflected light more efficiently, bigger LEDs that draw less power [3][4]. The Verge's reviewer called continuous heart rate "a genuinely helpful update for folks who might need to monitor heart rate due to chronic illnesses" [13].
Apple published a white paper putting its continuous heart rate against a Polar H10 chest strap and against the Pixel Watch 4, Galaxy Watch 8, Oura Ring 5 and Whoop, across several workout types and at rest [7]. The Verge did not reproduce it. "I'd need roughly eight arms and legs to replicate this study in a week, and alas, I'm not an octopus," the reviewer wrote [9]. What she did run was one strap over two runs, a walk and a rest period, and the Series 12 stayed within five beats per minute of the H10 the whole time, trailing it by about four seconds [8].
The Verge splits this year's updates in two: catching up to the AI health features the rest of the wearable market already shipped, and leading on wearables that surface information from your whole day [20]. The first half is in the box. The second half is Audio Intelligence, Apple's name for an upcoming suite of AI-powered ambient listening features, and the review says several of the most interesting health and AI features arrive later this year and were not available to test [12][11].
"Most of the ideas explored with the Series 12 aren't novel, but they haven't been implemented by a company with Apple's scale or reputation," the review said [14]. It describes the whole-day market Apple is walking into as "niche, nascent, and recently problematic", without naming a company in it [15][19].
The S11 handles microphone data in a secure exclave [2]. The Verge lists that privacy structure among the watch's strengths, and lists in the same review, under The Bad, that "Thoughtful privacy may not change how laypeople feel" [16][17]. Whoever hands this watch to a parent or a patient has to explain a wrist microphone that listens all day, and telling them the audio stays in a secure exclave will not reassure them.
The purchase comes in two columns. Column one is what a week of wearing can verify: five-second heart rate, faster charging, Siri queries that come back quicker than on an Ultra 3 [16][18]. Column two is Audio Intelligence and the later health features [11][12]. If the reason for the upgrade sits in column one, the evidence is already on the wrist and a chest strap will settle it. If it sits in column two, the decision date is whenever Apple ships, because the reviewer's week produced this: "After a week with the Series 12, I can't say I have a complete picture" [10].
What to watch
- Whether Apple attaches a firm date to Audio Intelligence and the later health features, and whether reviewers get them before buyers do.
- Whether anyone independently reproduces the device-by-device accuracy comparison in Apple's continuous heart rate white paper.
- Whether the readiness score changes its output once it has weeks of five-second data behind it rather than five-minute data.