O Apple Watch is, before a wrist computer, an excellent activity monitor. Thanks to its various features and advanced sensors, it is possible to check your heartbeat, make an ECG, monitor the blood saturation level and even body temperature – which can help with female health.
Many of these watch technologies are only possible thanks to heart rate and blood oxygen sensors. Both are located at the bottom of the device, so they are in direct contact with the user’s wrist.
So if you’ve ever come across any light leaking between your watch and your wrist, it’s directly linked to those two sensors.
What does a green light coming out of the back of the watch mean?
Green light means the heart rate sensor is actively working. The technology that Apple uses to make this measurement is called photoplethysmographic.
The idea here is simple: because our blood is red, light from it reflects red and absorbs green. With the watch’s array of green LEDs and light-sensitive photodiodes, it is possible to identify the amount of blood flowing through the wrist.
Typically, you will see this light in measurements taken in the background and also while you are doing some physical exercise.
What does a red light coming out of the back of the watch mean?
Red lights are directly related to blood oxygenation measurements (which is represented by a percentage of oxygen that red blood cells carry from your lungs to the rest of your body).
In addition to being measured by manually opening the Blood Oxygen app, this is also done in the background during the day and also if you are sleeping with your Apple Watch on.
If the red light bothers you at night or in Cinema mode, you can easily turn it off by going to the app Watch » Blood Oxygen and disabling “Foco Sleep” and/or “In Cinema Mode”.
It’s worth noting that the blood oxygen sensor is only available on Apple Watches Series 6 and later (excluding both SE generations).
Everything properly explained? ????
Apple Watch Ultra
Apple Watch Series 8
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