Mi Band 3: Tracking Sleep With Precision

The Mi Band series by Xiaomi is an affordable fitness tracker that can monitor daily activity and health metrics such as blood oxygen levels, stress, and sleep. The Mi Band 3, in particular, uses a combination of a proximity sensor and actigraphy (actimetric sensor) to detect sleep. It also uses a triaxial accelerometer and a photoplethysmography (PPG) sensor to detect movements and monitor blood volume changes, respectively. When the device detects no movement for a certain period of time, it starts recording sleep and classifies sleep into deep and light sleep based on body movements. While the Mi Band 3 has been found to accurately detect the time spent in bed, it has had difficulties in detecting wake periods, which affects its estimation of total sleep time and sleep efficiency.

Mi Band's sleep tracking accuracy

The Xiaomi Mi Band series uses a built-in accelerometer to detect motion and a heart rate sensor to estimate when you fall asleep. The Mi Band 3 can also track sleep duration, sleep and wake times, and sleep quality.

Some users have reported that the Mi Band 3's sleep tracking is accurate, especially when it comes to falling asleep and waking up times. However, others have noticed some limitations, such as the device not registering when the user wakes up in the middle of the night unless they get out of bed. The Mi Band 3 also does not currently offer smart alarms to wake the user during light sleep.

To improve the accuracy of sleep tracking, it is recommended to wear the Mi Band correctly, with the band snug on the arm but not too tight. Combining the Mi Band 3 with third-party sleep tracking apps like Sleep as Android can also provide more accurate sleep tracking and smart alarms.

While the Mi Band series may not be the most in-depth sleep-tracking solution on the market, it offers surprisingly useful sleep tracking features at an affordable price. The data gathered by the Mi Band can be used to improve your night routine and sleep quality.

Heart rate monitoring

The Mi Band 3 uses a PPG sensor to detect your heart rate from the surface of your wrist. This sensor works by shining infrared light to detect the blood flow rate in the portion of the skin illuminated with light. The Mi Band 3 also has improved heart rate monitoring features, allowing you to take an on-the-spot reading from the device itself by pressing and holding down the button on the band.

Within the app, you can view your resting heart rate data throughout the day and get details on your daily heart rate zone with a breakdown of that data into specific heart rate zones, along with maximum, minimum, and average heart rate readings. You can also set up high heart rate alerts and pace alerts (for outdoor running only), which send vibrations to the tracker when you enter those marked zones.

The Mi Band 3 also has an Assisted sleep monitoring feature, which increases the heart rate measurement frequency when the device detects you're asleep. This is especially helpful if you've set your heart rate monitoring interval to more than five minutes.

It's important to note that the sleep tracker on the Mi Band 3 is turned off by default to save battery life, so you'll need to switch it on in the settings. Additionally, the band should be worn snugly on your arm, but not too tight, for the most accurate readings.

Motion detection

The Mi Band 3 uses a combination of two sensors to track sleep: a proximity sensor and an actigraphy (actimetric) sensor. The actigraphy sensor, or built-in accelerometer, detects motion and is used to estimate when the user falls asleep. The accelerometer is a triaxial accelerometer, which detects movements in three dimensions.

The Mi Band 3 starts recording sleep when it detects no movement for a certain period of time. It uses the accelerometer to classify sleep into deep and light sleep based on body movements. The band has been found to be accurate in detecting the time spent asleep and awake, but less accurate in distinguishing between light and deep sleep.

The Mi Band 3's motion detection feature has been observed to only label a time period as "Awake" if the user gets out of bed and walks around. It does not seem to detect brief periods of wakefulness during the night, such as when the user wakes up in the middle of the night to check their phone.

To improve the accuracy of sleep data, it is recommended that the Mi Band 3 be worn correctly, with a snug fit on the user's arm but not too tight.

Sleep quality analysis

The Mi Band 3 uses a combination of a proximity sensor and actigraphy (actimetric sensor) to track sleep. It also uses a triaxial accelerometer and a photoplethysmography (PPG) sensor to detect movements and monitor blood volume changes, respectively.

The device starts recording sleep when it detects no movement for a certain period of time. It classifies sleep into deep and light sleep based on body movements and uses PPG for continuous heart-rate monitoring to track light and deep sleep more precisely.

The Mi Band 3's sleep quality analysis feature provides valuable insights into your sleep patterns. It contextualizes the data collected, offering snippets of information such as whether you got enough sleep or if your sleep quality was worse than usual. This analysis is based on the device's tracking of sleep duration, sleep and wake times, and sleep regularity.

To improve the accuracy of sleep data, it is recommended to wear the Mi Band correctly, with a snug fit on the arm but not too tight. Additionally, enabling assisted sleep monitoring in the Zepp Life app can increase the heart rate measurement frequency during sleep, providing more detailed information.

While the Mi Band 3 provides useful sleep tracking features, it is important to note that all fitness trackers have a margin of error. Therefore, focusing on general trends over time rather than spot accuracy is a more beneficial approach to interpreting sleep data.

Sleep tracking apps

The Xiaomi Mi Band series is an affordable fitness tracker that can monitor daily activity and health metrics such as blood oxygen levels, stress, and sleep. The Mi Band 3 uses a combination of a proximity sensor and actigraphy (actimetric sensor) to detect sleep. It also uses a triaxial accelerometer and a photoplethysmography (PPG) sensor to detect movements and monitor blood volume changes.

Like most smartwatches and fitness trackers, the Mi Band 3 uses a built-in accelerometer to detect motion and a heart rate sensor to estimate when you fall asleep. The PPG sensor is also used for continuous heart-rate monitoring during sleep to track light and deep sleep more precisely. The collected data is then converted to a hypnogram using the Mi Fit software.

To improve the accuracy of sleep data, it is recommended to wear the band correctly, with a snug fit on the arm but not too tight. The Mi Band 3 has been found to be as reliable as the Fitbit Sense 2 when it comes to sleep tracking, although it may struggle to recognize sleep stages. It is important to note that all fitness trackers have a margin of error, so it is better to focus on general trends over time rather than spot accuracy when interpreting sleep data.

In addition to the official Mi Fit app, there are other third-party apps that can be used with the Mi Band 3 for sleep tracking. One such app is Sleep as Android, which uses the heart rate monitor and possibly the movement sensor for sleep tracking. However, an extra app like the notification and tools app for Mi Band 3 may be needed for it to work with Sleep as Android. Another preferred app for tracking sleep with the Mi Band is Zepp Life, which provides a summary of sleep information on its home screen.

Frequently asked questions