Modern wearables have become an integral part of the lives of millions of people who are health conscious. Owners of Xiaomi devices often encounter the acronym BPM in the application interface or on the screen of the wristband itself, many users mistakenly believe that this is a technical term associated with data transfer or processor speed.
BPM is actually short for Beats Per Minute, which literally means "blows per minute." In the context of fitness trackers and smartwatches, it's the standard designation for heart rate, which is your heart rate, and understanding this parameter is critical for proper monitoring of physical activity and cardiovascular health.
In this article, we will discuss in detail how exactly the optical sensor works in the Mi Band and Amazfit devices, why the readings may differ from the real values and what settings will help you get the most accurate data about your heartbeat.
Principle of operation of the optical pulsemeter sensor
At the heart of Xiaomi's BPM measurements, it's photoplethysmography (PPG) technology, and there are LEDs on the back of the device that emit green light of a certain wavelength, which penetrates the skin and reflects off the blood vessels.
When the heart contracts, the volume of blood in the vessels increases, and the absorption of light changes. The sensor detects these microscopic changes in the reflected signal and converts them to a numerical value of BPM. The processing algorithm analyzes the frequency of the bursts, calculating the current rhythm.
The accuracy of the measurements depends on the density of the wrist, and if the wristband dangles, the lights scatter, and the sensor can't read the correct signal, which is why you need to wear the tracker tightly to get accurate BPM data, but without suppressing blood flow, about two centimeters above the wrist bone.
It is worth noting that the green color of LEDs was not chosen by chance: hemoglobin in the blood best absorbs the green spectrum, which allows you to minimize errors when moving your hand.
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Wear the bracelet just above the carpal bone, where the skin is thinner and closer to the vessels – this greatly improves the quality of the BPM signal reading.
Interpretation of BPM in Mi Fitness
After syncing with your smartphone, all your heart rate data is fed into the Mi Fitness app (formerly Zepp Life), where you see not just dry numbers, but full-fledged statistics. The main screen usually shows your current BPM, as well as your minimum and maximum values for the day.
The app automatically breaks the data into heart rate zones, which helps you understand whether your heart was working at rest, when burning fat or in the anaerobic zone, and your heart rate is calculated individually if you have specified your age and gender in your profile settings.
It is important to pay attention to the schedule of changes in BPM during the day.Sharp jumps without exercise can indicate stress, fatigue or health problems. The application also monitors heart rate variability (HRV), which is an important marker of recovery.
- 📊 Rest: The normal range is 50 to 90 beats per minute for an adult.
- 🏃 Activity: during exercise, the pulse can reach 140-170 BPM age-dependent.
- 🌙 Sleep: at night, the heart rate usually decreases to minimum values, which indicates a quality rest.
Frequency settings for measurements and notifications
By default, many Xiaomi bracelets measure their heart rate at 30 minutes or only during exercise, but for a more detailed analysis of daily rhythms, this setting can be changed. The more often you measure, the more accurate the statistics, but the faster the battery is used.
To change the settings, you have to open the app, go to the device profile, and find the health monitoring item, and you can choose Every Minute, Every 10 Minutes, or Smart Mode, and continuous monitoring is good for athletes, but requires daily charging.
You should also set up pulse threshold notifications, so if your BPM exceeds your set value (e.g., 120 beats) at rest, the bracelet vibrates, which helps you stop and reduce the load.
☑️ Optimal monitoring settings
⚠️ Attention: setting a 1 minute interval significantly reduces the autonomy of the device. If you do not need professional statistics, it is better to leave the interval of 10-30 minutes.
Factors affecting the accuracy of readings
Even the most advanced optical sensors are exposed to external influences. There are a number of factors that can distort the real values of BPM. One of the main enemies of accuracy is the tattoo on the wrist. The pigment under the skin blocks the light of the sensor, making measurements impossible or extremely inaccurate.
The low ambient temperature also affects the result: in cold, peripheral vessels constrict, blood circulation to the wrist slows down, and it is harder for the sensor to read the signal, in which case the readings may be underestimated.
Sweating and water on the surface of the sensor create an optical lens that scatters light. Before measuring or exercising, it is recommended to wipe the back of the bracelet with a dry cloth. Static electricity and bright sun can also interfere with the work of photodiodes.
| Influence factor | Effect on testimony | Recommendation |
|---|---|---|
| Tattoo on the wrist | Blocking light, lack of data | Wearing a bracelet above a tattoo or on the other hand |
| Low temperature | Vascular narrowing, underestimation of BPM | Warm your wrist before measuring |
| Free strap | Outdoor light, noise | Tighten the strap tighter |
| Bright sun | Sensor lighting, value jumps | Cover the bracelet with a sleeve of clothing |
Why does the bracelet show a pulse of 200 BPM?
Comparison of models: Mi Band vs. Amazfit
Xiaomi’s line of wearables includes both the simple Mi Band trackers and the more advanced Amazfit watches, and while the way they measure BPM is similar, hardware and software algorithms are different.
Older watches often feature additional sensors, such as those for measuring blood oxygen saturation (SpO2), which allows for more comprehensive analysis, and higher-frequency sensor surveys and a more powerful processor for processing signals in real time.
In budget models like the Mi Band 4 or 5, the algorithms average their readings over a longer period of time to save energy, so in fast interval training, they can show a pulse with a delay of 5-10 seconds.
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The Amazfit watch provides a more accurate and faster response when measuring BPM thanks to a more powerful processor and improved sensor optics compared to the base Mi Band models.
Solution: Why not measure pulse
If your bracelet has stopped showing BPM or the values seem absurd (for example, 0 or 255), first check the purity of the sensor. The fat from the skin, cream or dirt creates an opaque film.
The second step is to reboot the device. Sometimes the software module responsible for collecting telemetry freezes. Rebooting through the settings menu or disconnecting from charging often solves the problem. Also make sure that the firmware version is relevant, since Xiaomi regularly releases patches that improve the algorithms of the pulsemeter.
In rare cases, resetting the bracelet to the factory helps, before you do this, make sure to back up the data in the application. If nothing helps, perhaps the optical module itself has failed, and you need to contact the service center.
- 🧼 Cleaning: regularly wipe the sensor with a soft cloth.
- 🔄 Update: Check for new firmware in the app.
- 📱 Reconnect: Remove the device from Bluetooth and add again.
⚠️ Warning: If the bracelet shows pulse 0 BPM And for a long time, even after you've restarted, don't ignore it. Check the other hand. If the problem persists, it's probably a hardware breakdown.