The principle of the pulsemeter in smart watches and bracelets Xiaomi: from the sensor to the application

Introduction: Why do you need a pulsemeter in Xiaomi gadgets?

The pulsemeter in Xiaomi smartwatches and fitness bracelets is one of the key features that transforms the device from a simple accessory into a full-fledged health assistant. But how does the small sensor on the back of the gadget manage to measure heart rate (HR) through the skin? And why does readings sometimes seem inaccurate?

In this article, we will take a closer look at the optical pulse meter used in the Mi Band, Xiaomi Watch and other wearables of the brand, learn what technologies are involved, how data is processed, and what affects the accuracy of measurements, and learn how to use the function correctly to get the most reliable results.

Spoiler: it's not magic, it's a complex combination of optics, algorithms and physiology. And yes, your wrist tattoo can interfere with measurements -- but more on that later.

PPG Technology: How Light Helps Measure Your Pulse

The heart of Xiaomi's pulsemeter is photoplethysmography (PPG), a technique that uses light to analyze blood flow. Unlike medical pulsemeters with electrodes, everything works non-contactly through the skin.

Here's what happens inside the device:

• 💡 LEDs (usually green) illuminate the skin on the wrist, and the green light is not chosen by chance, it is best absorbed by hemoglobin in the blood.
• 🔄 The photodiode picks up the reflected light, and when the blood pulsates in the vessels, the intensity of the reflected light changes.
• 📊 The microprocessor analyzes these changes and converts them into digital pulse rate data.

Fun fact: some Xiaomi models (e.g. Mi Band 7 Pro or Xiaomi Watch) S3) multichannel PPG-This is a multi-LED sensor, which allows you to reduce the error and take into account the movements of the hand.

But why does it sometimes jump? PPG-method is sensitive to external factors:

• 🏃‍♂️ Hand movement – when running or shaking, the sensor can read not the pulse, but vibrations.
• 🌡️ Skin temperature – cold constricts blood vessels, and the signal becomes weaker.
• 🎨 Tattoos or dark skin – pigments absorb light, interfering with the sensor.

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If you have dark skin or a tattoo on your wrist, try wearing the bracelet a little higher (2-3 cm) – this can improve the accuracy of measurements.

Data processing algorithms: how Xiaomi filters noise

Raw data with PPG-The sensor is a chaotic signal, where the pulse is mixed with artifacts (movement, interference). To get accurate readings, Xiaomi uses complex filtering algorithms. Here's how it works:

1. Noise removal: The program sifts out high-frequency interference (e.g. from hand tremors) and low-frequency interference (breathing, slow movements).
2. Wave shape analysis: The algorithm looks for characteristic peaks corresponding to heartbeats.
3. Correlation with the accelerometer. The motion sensor helps you separate the real pulse from the artifacts. For example, if you wave your hand, the gadget will realize that it's not a rapid heartbeat.
4. Comparison with baseline data: The device takes into account your age, weight and previous measurements to adjust the result.

Xiaomi models from 2022 (e.g. Mi Band 7 and newer) use an algorithm AI-pulse analysis, trained on thousands of hours of real-world data, and this reduced the error to ±2 beats per minute at rest.

But algorithms are not all-powerful, for example, in arrhythmia (irregular heart rate) or atrial fibrillation, accuracy is reduced, because it is difficult for the program to identify a clear pattern, in which case the gadget can show an average value or give an error.

Measurement accuracy: How much can data be trusted?

The question that many people are concerned about is, how accurate is the pulsemeter in Xiaomi? The answer depends on the measurement conditions. Here's a comparative error table in different scenarios:

To test accuracy, you can compare Xiaomi readings with a medical pulsemeter or measure your pulse manually (on the wrist or neck) for a minute. If the difference is more than 10 beats per minute at rest, you should check the density of the sensor or update the firmware.

⚠️ Note: The pulsemeter in a smartwatch is not a medical device, its data are indicative and cannot be used to diagnose diseases.

How to measure the pulse on Xiaomi: step-by-step instructions

To get the most accurate data, follow these recommendations:

Wear the bracelet 2-3 cm above the wrist bone (not on the bone itself!) | Make sure the sensor fits tightly to the skin but does not hold your hand | Measure your resting heart rate (sitting or lying down) for baseline values |Do not measure your heart rate immediately after eating, coffee or alcohol | Check that your hand is free of dirt, cream or tattoos under the sensor-->

For manual measurement:

1. Open the menu on the bracelet (swipe up on the Mi Band or click the button on the Xiaomi Watch).
2. Select the Heart Rate (Pulse).
3. Do not move your hand for 10-15 seconds while the measurement is taking place.
4. The result will be displayed on the screen and synced with the Mi Fitness or Zepp Life app.

For continuous monitoring (e.g. during sleep or exercise):

• 📱 In the Mi Fitness app, go to Profile → Settings of the device → Monitoring of heart rate.
• 🔄 Select mode: Auto - Measurement every 5-30 minutes (depending on model); Manual - only on request; Continuous - every minute (severely reduces battery life).

⚠️ Attention: Continuous monitoring of the pulse can reduce the battery life of the bracelet by 30-50%, and use this mode only when necessary (for example, during a marathon or if you suspect arrhythmia).

Comparison with other brands: who is more accurate?

PPG technology is used in all popular fitness bracelets, but implementations differ. Here's how Xiaomi pulsemeters compare to competitors:

As you can see, Xiaomi isn't leading in accuracy, but offers a better balance of price and functionality.For professional athletes, it's better to consider Garmin or Polar, but for day-to-day monitoring, the Mi Band is more than enough.

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If you want medical accuracy, use a chest pulseometer (like the Polar H10) and wearables are suitable for trends and general monitoring, but not for diagnosis.

Common Problems and Their Solutions

Even with modern algorithms, users sometimes encounter inaccurate readings, and here are typical problems and ways to solve them:

• 🔋 The pulse meter is not working or showing "---" Check the bracelet's adhesive density - there should be no gap between the sensor and the skin. Update the device's firmware through the Mi Fitness app. Reboot the gadget (on Mi Band: press the touch button for 10 seconds).
• ❤️‍🔥 Indications too high (180)+ I'm sure the sensor reads your hand movements. Try measuring your pulse sitting down with your hand on the table.
• 📉 Pulse is unstable (jumps 60 to 120 in a few seconds) This may be due to arrhythmia or poor sensor contact. Try changing your arm. Turn on continuous monitoring for 5-10 minutes to see the mean.
• 🛌 Make sure your sleep monitoring and sleep heart rate are on the settings. Wear a bracelet 1-2 cm above your wrist, so it interferes less and reads data better.

If problems persist, try resetting the bracelet to factory settings (in Mi Fitness: Profile → Device Settings → Reset) and in 90% of cases, this helps to return the accuracy of measurements.

FAQ: Answers to Frequent Questions