In the era of total digitalization of health, smart scales have become an essential attribute for millions of people who monitor their physical fitness. Users of the Xiaomi ecosystem often wonder about the reliability of the data obtained, because deviations even in 100-200 grams can significantly affect motivation and adjustment of the training plan. Manufacturers claim high accuracy of sensors, but real practice makes its own adjustments in the form of various external factors.
In this article, we will take a closer look at how the Mi Body Composition Scale and Mi Smart Scale 2 work, and answer the main question: how much can you trust them in everyday life, you will learn what errors are considered normal for household appliances, and when to sound the alarm or recalibrate the device.
It's worth noting that perfect accuracy at home is almost impossible to achieve because of the variability of the operating conditions. However, with a few simple rules, Xiaomi's electronic scales show a stable result comparable to professional equipment at the entry level. It is important to distinguish the systematic error of the device from the natural fluctuations in the weight of the human body during the day.
Principle of operation and measurement technology
The basis of the accuracy of any smart scale, including Xiaomi products, is a high-precision pressure sensor (tensor). Current models such as the Mi Body Composition Scale 2 use an advanced version of the MnPC sensor, which is able to detect changes in mass increments of up to 50 grams, which means that the device can theoretically respond to even a sip of water drunk immediately before weighing.
But beyond just weighing, these devices use bioimpedance analysis to determine body composition, and through electrodes on the surface of the scale, a weak, imperceptible electric current is passed. Because muscle tissue contains more water and electrolytes, it conducts current better than fat, and it is based on tissue resistance that the Mi Fit or Zepp Life algorithms calculate the percentage of fat, muscle and water.
⚠️ Attention: Bioimpedance has limitations, and the indications may be incorrect if the user has a metal implant, a pacemaker, or if he is pregnant.
To ensure stability, a board is installed inside the case with a microcontroller that processes signals from sensors and transmits them to a smartphone using Bluetooth Low Energy protocol. The quality of soldering and calibration of sensors in the factory directly affect how the readings will differ from the reference values. Xiaomi devices use automatic calibration on each turn on, which minimizes the risk of error accumulation.
Technical details of sensors
Factors affecting the accuracy of readings
Even the most sophisticated device can't tell the truth if the operating conditions are broken. The first and most critical factor is the surface on which the scales are standing. Carpet coating, soft-backed linoleum or just plain uneven flooring cause the platform to skew, and the pressure sensors to fire incorrectly, and you can get a range of up to 1-2 kilograms on repeated weighings.
The second important aspect is the position of the user's body: you need to stand strictly in the center, spreading the weight evenly between the two legs. If you lean on one leg or touch surrounding objects, the measurement result will be distorted. Xiaomi algorithms are designed for the static position of the person, so any movement during the measurement (even transfer) can knock down the calculation of bioimpedance.
- 📏 Hardness of the base: scales should stand only on a hard, flat floor (tiles, laminate, parquet).
- 👣 Stop position: feet must be strictly on metal contacts for proper current flow.
- 🌡️ Temperature: sudden temperature changes in the room can temporarily affect the operation of electronics.
Static electricity and humidity can also be used to create a charge on the surface of plastic that is too dry, and regular dry rags can help avoid dust buildup and static charge, which is especially true for glossy-coated models.
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Rub the surface of the scales with a dry microfiber before each use. Dust and villi can create a micro gap between the foot and the contacts, degrading the quality of the bioimpedance signal.
Mi Smart Scale vs. Body Composition Scale
Xiaomi’s weight range has been extended over several generations, and it’s important to understand the difference between the two: The Mi Smart Scale (often referred to as the first version) only measures weight and BMI. It has good accuracy within the stated 50 grams, but lacks body composition analysis, as it lacks additional electrodes to supply current.
The Mi Body Composition Scale and its updated Scale 2 offer enhanced functionality, with accuracy not only dependent on the strain gauge, but also on the quality of the calculation algorithms. Users often note that there may be differences in weight when switching from the first model to the second, although both are formally functional, due to different sensor calibration and updated software processing.
| Characteristics | Mi Smart Scale 1 | Mi Body Composition Scale 2 |
|---|---|---|
| Step of measurement | 50g | 50g |
| Weighing range | 5 - 100 kg | 5 - 150 kg |
| Analysis of body composition | No. | Yes (8 parameters) |
| Type of sensor | Tenzometer | High-precision MnPC |
If you want to control weight, the first model will do the job as well as the top models, and if you are interested in the dynamics of changes in muscle and fat mass, the version with the prefix "Body Composition" will be the only choice, despite the slightly more complex calibration procedure.
Errors and tolerances
Each measuring device has its own class accuracy. For household electronic scales, the standard is an error in the range from 100 to 300 grams. If the difference is less than 200 grams when re-weighing (with full descent and re-standing on the platform), then the device is considered completely serviceable and accurate.
More significant discrepancies, such as 500 grams or more, can indicate problems, such as a discharged battery that does not provide stable voltage for the circuit to work, or mechanical damage to the sensors after a fall, and it is worth considering that the scale can “float” at a very low weight (less than 5 kg), since this is the lower limit of their sensitivity.
In the context of bioimpedance analysis, the margin of error may be higher, especially in terms of fat and muscle mass, where a 1-2% variance is considered normal, depending on the level of hydration of the body, so it makes sense to compare readings only in the same conditions: in the morning, on an empty stomach, after going to the toilet.
⚠️ Warning: Do not try to calibrate the scales manually by placing known weights (dumbbells, weights) on them, this will knock down the factory settings of the strain gauges and lead to irreversible loss of measurement accuracy.
Calibration and adjustment for maximum accuracy
The proper operation begins with installation. Once you have placed the scales on a flat, hard floor, you need to press the switch on (or just stand on them if the model is automatic) for them to turn on. Wait for zeros to appear on the display, which is a signal that the automatic calibration has been completed and the device is ready for operation.
If you move the scales to another location, you need to repeat the on and off procedure, and many users ignore this step by standing on the dormant scale, which leads to erroneous initial readings. The right sequence of steps ensures that the measurement algorithm starts from the correct starting point.
☑️ Proper weighing procedure
Second-generation models also need to synchronize with the app. Make sure the user profile correctly identifies height, age and gender. This data is used by formulas to calculate body composition, and an error in them will lead to misinterpretation of the data, even if the weight itself is measured perfectly accurately. Updating the firmware of the scales through the app can also improve the stability of the Bluetooth module.
The impact of external conditions on the work of electronics
Xiaomi’s electronics are sensitive to environmental conditions. A cold floor (such as in an unheated bathroom in winter) can temporarily reduce the accuracy of strain gauges before they are warmed up. Similarly, direct sunlight falling on a display or body can cause the batteries to overheat and distort readings.
Humidity is another enemy of accuracy. Although scales have spray protection, high humidity in the bathroom can lead to oxidation of contacts or condensation inside the enclosure. It is recommended to store the device in a dry place or ensure good ventilation of the room. Regular replacement of batteries (every 6-12 months) will also prevent voltage surges that affect the operation of the measuring circuit.
In the long run, the accuracy of the scales may be reduced by the natural wear of the mechanical parts. If you notice that the range of readings during triple weighing consistently exceeds 300-400 grams, perhaps the life of the strain gauges is coming to an end, in which case buying a new model will be a more rational decision than trying to repair.
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Weighing conditions are more stable than the absolute accuracy of the instrument, weigh them at the same time, in the same place, to track the actual dynamics of weight changes.