On what basis does the smart bracelet measure our sleep time and analyze the changes in our sleep depth?

Everyone goes to bed and actually falls asleep, the body will always have a variety of changes, the bracelet is worn on the wrist, will inevitably produce a variety of displacements with changes in body movement, the gravity point changes, the bracelet Will record and judge whether the person is sleeping.

During deep sleep, the muscles will relax, and the limbs will not produce large movements; while during light sleep, the human body will produce some slight movements. By monitoring the movement status, the smart bracelet can thus determine whether the human body is in a deep sleep state.

However, deep sleep does not mean that the body is in a "stationary" state. Some people will still have the habit of turning over even if they have entered deep sleep. As long as the smart bracelet records that the body has "moved up", the system will think that the person and Did not sleep soundly. Therefore, it is not surprising that some people have recorded a deep sleep time of only a few minutes per night on the smart bracelet. The bracelet does not rely on light to recognize sleep.