Patent hints at fixing Apple Watch’s heart-rate monitor

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Apple Watch
Writing about patents always gets the blood pumping around here.
Photo: Evan Killham/Cult of Mac

The Apple Watch’s heart-rate monitor is pretty damned cool, but it’s the one piece of the new smartwatch that’s seeing the most updates and tweaks since the hardware launched seven weeks ago.

A new patent suggests that Apple has even more changes in store for the health tech.

The filing, which comes courtesy of Patently Apple (don’t look directly at the headline on that article), outlines a process for the Apple Watch to calculate heart rate based on readings from two diodes. But big surprise, right? That’s how the thing already works. But that’s not all.

Apple’s patent describes a method to gather heart-rate data by analyzing data from one diode that is in contact with the skin and one that is not. And that could make the readings even more accurate.

Currently, your Apple Watch flashes green light onto your skin and then reads the fluctuations in how well your blood absorbs it as your heart beats. You have more blood in your skin during beats, which soaks up more green light, and the Watch counts those spikes to determine your pulse.

The first watchOS update had users wondering if the new software had broken their gear, with the promised “every 10 minutes” monitoring modified to be “every 10 minutes, unless you’re moving.” Apple stripped out the feature to maintain maintain accurate resting heart rate readings. If you use the Watch’s Workout app to tell it you’re exercising, however, those green lights will stay on constantly.

The current system depends on the light sensors maintaining contact with the skin, and during an exercise, it’s possible that the Watch could shift of move and affect accuracy. But this update could solve that problem and ensure clear readings even if you’re bouncing around like a crazy person. It’s not clear if this method of sensor-reading is possible on the current version, however, but if Apple decides to follow through with it, we can certainly expect it in the Apple Watch 2.