A tattoo on your wrist or an Apple Watch, you will have to choose: shortly after the availability of the long-awaited smart watch from Apple, comments poured in on Reddit, Twitter and other media to highlight the problem encountered with the watch when it is in contact with tattooed skin.
In cause, loss of connection and heart rhythms far from reflecting reality or any precision when the watch's sensors are placed on tattooed skin.
The situation is all the more constraining as the Apple Watch asks for a security PIN code each time it detects having left the wrist of its owner. iMore has conducted tests on various skins to try to highlight the dysfunctions.
The site arrives at the result that the darkest and most saturated colors cause many problems of reading the heart rate in the tattooed (up to 196 beats per minute at rest)
Tattoos with softer or partially faded colors would pose much less Apple Watch problems, only the cardiac sensor would encounter some difficulties.
Apple has made it clear on its website that a small proportion of users may experience heart rate reading problems with the watch, but does not mention any relationship to being tattooed.
The firm, however, responded to the mini-controversy by explaining the technology at work for monitoring the heart rate. The watch thus uses green LEDs associated with photodiodes to detect the quantity of blood which passes through the wrist of the user during a given period of time. Depending on the amount of green light absorbed by the blood (the latter is red, because it reflects red light and absorbs green light), the watch is able to define the user's heart rate.
This technique is adopted by other devices such as the Fitbit Charge HR or the Microsoft Band. Having a tattooed wrist thus represents a constraint for this technology, since the pigments colored in the skin of the user distort the data collected by the sensor.
Fortunately, there is a solution for users who cannot read their heart rate correctly with the Apple Watch. However, it requires investing a little more by opting for a Bluetooth heart monitor worn at chest level.
Currently, it is impossible to know if a software update could allow the user to correct the sensitivity of the watch's heart monitor.