In an era where drinking water quality is a daily concern, Xiaomi’s compact devices are increasingly on the shelves of electronics stores, and many users, when they first see the gadget, wonder what it measures and can you trust its readings?
In fact, we are not talking about a complex laboratory analyzer, but about a specialized one. TDS-This device is designed to quickly assess the total salt content of a liquid, which is an indirect indicator of its purity from mechanical impurities and salts.
Understanding what Xiaomi's water tester shows will help you avoid buying unnecessary filters or replacing the cartridge in the cleaning system in time. Let's get a glimpse of the physics of the process and the numbers on the screen.
The principle of operation and physics of measurements
The basis of any TDS-Meters including models from Xiaomi (Mijia) TDS Pen, which is a method of electrical conductivity, is that pure distilled water conducts virtually no electrical current, but once it dissolves salts, minerals or metals, it becomes a conductor.
The device is lowered into the liquid, and the two electrodes at its end give a weak electrical signal. The resistance of the water varies with the concentration of ions. The more of them, the better the current is conducted and the higher the final value on the display.
It's important to understand that the device doesn't see viruses, bacteria or organic compounds directly, it only reacts to charged particles. TDS-Meter shows total mineralization, not biosafety.
Can the device detect the hardness of water?
Decoding of indicators: TDS value table
When you put the probe in a glass of water, the number lights up on the screen. The unit of measurement is mg/l (ppm). But what do these numbers mean in terms of safety and taste?
For quick reference, there's a universally accepted scale developed by the World Health Organization that helps you determine whether water is drinkable or better filtered.
| TDS indicator (ppm) | Water quality | Recommendation |
|---|---|---|
| 0 – 50 | Low mineralization | Perfect for drinking (reverse osmosis) |
| 50 – 150 | Medium mineralization | Optimal for daily use |
| 150 – 300 | High mineralization | Suitable, but it can be tough. |
| 300+ | Very high. | Requires cleaning or boiling |
Water with a value of about 100-150 ppm is often considered the most delicious and healthy, as it contains essential minerals. completely "dead" distilled water (0 ppm) is not recommended for constant drinking.
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The TDS norm for drinking water varies between 50-300 mg / l. Values above 500 mg / l make the water unsuitable for continuous use without additional filtration.
What exactly does Xiaomi TDS Pen measure?
Many people mistakenly believe that this gadget is a universal dirt detector. It's not. Let's list what kind of substances the sensor responds to.
- 💧 Dissolved salts (chlorides, sulfates, carbonates).
- 🧪 Metal ions (calcium, magnesium, sodium, potassium).
- 🏭 Heavy metals (lead, copper - in the form of ions).
- 🚫 Some organic compounds, if they dissociate into ions.
The device will not show the presence of chlorine (unless it is in the form of chloride ions), pesticides, herbicides, bacteria, viruses or microplastics, but will require chemical reagents or microscopes to detect them.
The main task of the Xiaomi TDS Pen is to control the operation of reverse osmosis filters. If the water shows the same numbers after the filter as from the tap, then the filter membrane has failed.
⚠️ Note: Do not use a tester to test distilled water in batteries or to refill irons immediately after purchase. Factory calibration may give a small error, and the "zero" device may not immediately show.
Instructions: how to use the tester correctly
The use of the instrument is as simplified as possible, but there are several nuances that ensure accuracy of measurements, and a violation of the measurement technique can lead to erroneous data.
First, remove the protective cap from the bottom of the device, and inside you'll see two metal electrodes, and don't touch them with your fingers before you measure them, because fat and sweat can distort electrical conductivity.
☑️ Water measurement algorithm
Do not immerse the appliance completely, the maximum depth of immersion is usually limited by risk or electrode length (about 4-5 cm).
Once you get the data, be sure to wash the electrodes with clean water and wipe with a soft cloth. The salt residue on the sensor can crystallize and damage the coating the next time you turn on.
Checking filters and cleaning systems
This is probably the most useful use of the gadget in the home. TDS-You stop blindly changing the cartridges on timer and do so after contamination.
The test is simple: measure tap water (e.g. 250 ppm), then water after a filter jug or flow system, and if the filter works, the rate should drop significantly.
For reverse osmosis systems, the drop should be almost tenfold, and if you have 200 ppm in and 180 ppm out of the osmosis tank, you have to replace the membrane, and that saves money and nerves.
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Record the readings of the new filter at the time of installation, and this will create a baseline (“zero”) from which you will track the wear of the cartridge in the future.
It's also useful for testing bottled water, and often unscrupulous manufacturers bottle ordinary tap water, and the tester will instantly tell you the difference between the declared mountain water and the reality.
Typical errors and limitations of the device
Despite its popularity, the Xiaomi TDS Tester has its limitations, and users’ biggest mistake is waiting for a full chemical lab in a pocket case.
Water temperature affects readings. Although Xiaomi has a temperature compensation system (ATC), extreme hot or cold water can give an error. The optimal temperature to measure is room temperature.
- 📉 Do not measure boiling water - you can damage the sensor and get incorrect data.
- 🥤 Do not check soda or juices – high content of sugars and acids will “cheat” the sensor.
- 🛁 Do not use to test pool water (high chlorine can oxidize electrodes).
⚠️ Warning: If the tap water measurement shows a 0 or 1, check the battery.