Some people sporting arm and wrist tattoos are discovering the new Apple watch will not work on their arms. According to one website, the heart rate sensor malfunctions if the watch is worn over some tattoos on a user’s wrist.

The problem was discovered by an Apple Watch owner and reported in detail on a reddit thread. The problem with the Watch not detecting a person’s heart beat is essential to the device working properly, and it seems to be centered around the color of the ink in the tattoo.

The problem is serious enough that Applecare was notified and the technical issue was reported to engineering, according to the blog written on reddit. The issue has since been confirmed by Apple blog iMore that the malfunction stems from the heart rate reading technology. Who would have known that?

So what is this technology that allows the Apple Watch to read your heart rate? It is called photoplethysmography. Or, in simpler words, a method that makes use of sensors on the back of the watch. They fire a combination of visible (green) and infrared (red) light at your skin. This light is absorbed and reflected back by your blood as the heart beats. The Watch measures the space between heartbeats, and the sensors can then determine your heart rate.

According to Apple, tattoo ink is opaque, meaning outside light is unable to penetrate through skin that has been tattooed. Solid black tattoos, which absorb both green and red light, will cause the watch to malfunction, as will red tattoo ink, which will only absorb the green light but reflects back the red light. When the watch does go haywire, it locks up and will not send any notifications. Users also lose some of the watch’s apps and functions, especially Apple Pay and the ability to make phone calls… see more

source: digitaltjournal