With Digital Crown, Apple Watch Series 4 Now Measures Your Heart Rate More Accurately

Apple has enabled ECG feature in watchOS 5.1 and is currently available only to US users over the age of 22. Although this feature has not been extended to more markets, Apple Watch Series 4 users around the world should now have gained a better heart rate measurement experience. (Via 9to5mac)



Traditionally, Apple Watch's optical heart rate sensor uses photoplethysmography, which uses a Green LED light with a light-sensitive photoreceptor to detect blood flow through the wrist at any point in time. With hundreds of flashing LEDs per second, Apple Watch can calculate the number of heartbeats per minute.

However, users can check their heart rate at any time with Apple Watch's Heart Rate app and put your finger on the Digital Crown, what this will do is that it creates a closed circuit between the user's heart and arms to capture electrical impulses through the chest. At this point, the user gets readings faster and with higher accuracy—getting one measurement per second instead of every 5 seconds.

When you use this method to record heart rate, the Health app on the iPhone will notice the use of electrode capture measurements, indicating "ECG" as the source. So now with the feature, I would say this is probably the most reliable heart rate monitor on your wrist.
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