2. Click "Display and screen brightness".
3. Click the option that the screen is always on.
4. After entering, check that it is always on.
5. After being turned off, the battery power supply of Iwatch is greatly saved and the service life of the battery is prolonged. The watch will automatically switch between invisible light and visible light according to the sleeping and waking scenes to monitor the heart rate. Invisible light is mainly used for heart rate monitoring during sleep, while green light of PPG is still used for heart rate monitoring in non-sleep scenes.