The Apple Watch Ultra 4 Has a Hidden Upgrade…
At first, I was pretty disappointed with the Apple Watch Ultra 4. It didn’t seem like Apple changed much.
But there’s one upgrade that’s easy to miss, because you won’t find it by looking at the screen or the outside of the watch. You have to flip it over.
Ultra 4 vs. Ultra 2
Put the Apple Watch Ultra 4 next to the Ultra 2 and look at the bottom. There’s a subtle but pretty significant difference in the sensor layout.
That area on the back of the watch is responsible for measuring your heart rate, and understanding what Apple changed starts with understanding how it works.
How the Heart Rate Sensor Works
The green LEDs on the bottom of the Apple Watch shine light into your skin.
As blood flows through your wrist with every heartbeat, the amount of light that gets absorbed and reflected changes. Photodiodes measure the light that bounces back, and the watch uses those changes to calculate your heart rate.
And that’s the part Apple redesigned on the Ultra 4.
Apple Redesigned the Sensor
On the Ultra 4, the photodiodes are packed into a much tighter ring compared to the Ultra 2. The LEDs are also larger, but there’s another noticeable change surrounding them.
That large pattern around the sensors is part of the electrical heart sensor used for ECG measurements. Altogether, the layout on the back of the Ultra 4 looks considerably different once you know what you’re looking at.
The idea behind the redesign is better and more frequent heart rate readings, making what initially looks like a small hardware change much more meaningful.
Final Thoughts
The Apple Watch Ultra 4 might not look dramatically different at first, but this is the kind of upgrade that matters more than a cosmetic change.
It’s hidden underneath the watch, and most people may never notice it. But for something designed to constantly monitor what’s happening on your wrist, improving the sensor hardware is a pretty significant change.
See you in the next article!
