Apple Watch found that possibly does not work well with tattoo in arm

When putting tattoo in the arm, you are measuring "heart rate"Apple WatchSensor does not work well and there is a possibility of malfunctioning, a site that summarizes Apple productsIMoreIt reports.

Apple Watch, heart rate sensors, and wrist tattoos: What you need to know! | IMore
http://www.imore.com/heres-why-apple-watch-does-not-play-nice-with-some-tattoos

Depending on your arm's tattoo, you can check the actual situation where Apple Watch is not working well with the following movie.

Apple Watch - Tattoo-gate! - YouTube


Attach Apple Watch to the arm with no tattoo and start data measurement at the time of walking.


Twist the wrist ......


When I look at the screen of Apple Watch again ......


The stopwatch which measures the time goes without trouble.


Next, attach Apple Watch to the arm with the tattoo and measure the data in the same way.


Twist your wrist and look at the Apple Watch screen again ...


Stopwatch is stopped for some reason.


And suddenly the application switched to the screen when paused.


In the next moment the stop watch began to move. It does not touch anything after starting the measurement, but it seems as though someone is being operated without permission.


I will try out whether Apple Watch does not work under different circumstances. Turn off the lock attached to the Apple Watch with an arm that does not put a tattoo.


The lock is released without any problem.


Twist the wrist ......


I will see the screen of Apple Watch again. The lock is released.


Of course you can also use the application. This is normal behavior.


Try to check the operation of Apple Watch with the arm with the tattoo.


Enter passcode and unlock.


This is the same as if you do not have a tattoo.


Twist the wrist ......


Looking at the screen of Apple Watch, it is locked.


This problem is related to the mechanism that Apple Watch measures heart rate. According to Apple support, Apple Watch measures heart rate with the following mechanism.

Heart rate. The meaning and display method in Apple Watch. - Apple Support
https://support.apple.com/ja-jp/HT204666

The heart rate sensor of Apple Watch measures heart rate using a method called photoelectric volume pulse wave recording method (photo plethysmography). This technology is based on a very simple fact that the name is complicated, but "blood is red because it reflects red light and absorbs green light". Apple Watch combines a green LED light and a photosensitive photodiode to detect the amount of blood flowing through the wrist. When the heart beats the beat, the blood flowing through the wrist increases, more green light is absorbed, while the amount of light absorption decreases between beating and beating. Apple Watch flashes the LED light hundreds of times every second, and measures the number of times the heart beats in a minute, that is, heart rate.

Heart rate sensor also uses infrared light. This mode is used when heart rate is measured every ten minutes, but when the infrared system can not obtain a reasonable measurement value, it switches to the green LED. Also, if the signal is weak, it will be compensated by increasing the brightness and sampling rate of the LED.

When tattoos are put in, ink pigmentation disturbs reading of heart rate of Apple Watch and it does not work well.

Then, iMore conducted an experiment on how much heart rate difference is actually produced between the arm with tattoo and the arm without tattoo. As a result, in the case of no tattoo, the heart rate is 69 times per minute, in the case of the arm with yellow or orange tattoo, the heart rate is 79 times per minute, the heart rate is slightly higher in tattoos It got more.


Were you just being nervous? Although it is such a difference that it thinks that it is thought, in the case of black and red tattoo, the heart rate was 196 times, and the change appeared visibly.


In the case of a person who puts tattoos of colors close to black on their arms without gaps, it is highly likely that Apple Watch will not work. In addition, in the case of natural pigmentation, it does not interfere with heart rate measurement, and there is no problem.