The quality of tap water is often questioned by smart appliance owners, especially when it comes to filling humidifiers, steam generators or just drinking water. Xiaomi TDS Pen has become the standard for quick clean-up testing, allowing you to see in seconds how effective your filters are. This compact gadget measures the total salt content, which is critical for extending the life of heating elements of household appliances.
Many users buy a device but don’t know the intricacies of its operation, which is why they get inaccurate data or face rapid battery discharge. In this article, we will discuss how to use the Xiaomi water tester correctly to get reliable readings in ppm. You will learn about the nuances of calibration, interpretation of results and features of sensor care.
Using the device correctly not only helps to monitor health, but also saves money on replacing cartridges in reverse osmosis systems. The accuracy of readings depends on the water temperature and the purity of the probe, so ignoring these factors can lead to mistaken conclusions about the suitability of water. Let's look at all the stages of working with this useful gadget from the Mijia ecosystem.
Principle of operation and decoding of TDS indicators
Before you start measuring, you have to understand the physical nature of the process, and TDS stands for Total Dissolved Solids, which translates to "total salt content." It doesn't see viruses, bacteria or organic impurities, it measures the electrical conductivity of water, which is directly related to the amount of dissolved inorganic salts.
The measurement is shown in units of ppm (parts per million) — particles per million. The higher this figure, the more dissolved substances in water. For household needs, there are generally accepted standards that help you navigate the numbers on the display screen.
- 💧 0-50 ppm – high-purification water, ideal for humidifiers and steam generators.
- 💧 50-150 ppm – optimal mineralization level for drinking water after filtration.
- 💧 150-300 ppm – hard tap water that requires cleaning before use.
- 💧 300+ ppm – water with high mineralization, often requiring the use of reverse osmosis systems.
⚠️ Attention: Low indicator TDS The tester does not detect heavy metals in bound form, pesticides or bacteria. For complete safety, use additional cleaning methods.
Importantly, the Xiaomi TDS Pen features a built-in temperature compensator, which means that the device automatically adjusts readings based on the temperature of the liquid, as the electrical conductivity of the water changes when heated or cooled, making measurements more accurate than cheap counterparts without such a feature.
First start and preparation for measurements
The device comes in minimalist packaging and usually already has a battery installed, protected by an insulating film. Before first use, you need to remove this film from the end of the cap to activate the power. The screen should catch fire, showing the current charge level and readiness to work.
To start measuring, remove the protective cap from the bottom of the device, and inside you'll see two metal electrodes that will contact the water, and don't touch them with your fingers, and don't let any fat or dirt get in, because that will distort the results.
☑️ Readiness of the device
Put the probe into the water to the depth of the Max tag, which is applied to the body. Do not dive deeper, otherwise water can get inside the case and damage the electronics. After diving, press the switch on once to activate the screen or hold it if the device has gone into sleep mode.
The readings on the display will start to change in real time. Wait for the numbers to stabilize — usually it takes 3 to 5 seconds. When the value stops jumping quickly, you can record the result. To save battery power, the device will automatically shut down after 10 minutes of inactivity.
Instructions: How to conduct measurements correctly
The technique seems simple, but it has its nuances: To get representative data, the water must be stationary. If you're measuring tap water, put it in a clean glass and let it stand for a couple of minutes to let the air bubbles come out and stabilize the temperature.
Put it down. TDS-If you're a meter into a liquid, spin it slightly to remove air pockets that can get stuck between electrodes, air bubbles create resistance and can understate the actual readings. Hold the device upright without touching the walls of the container.
| Object of measurement | Expected output (ppm) | Action. |
|---|---|---|
| Tap water | 150 - 400 | Filtration required |
| Filter-jug | 100 - 250 | Softening, but salts remain |
| Reverse osmosis | 5 - 30 | Perfect for technology. |
| Bottled water | 20 - 150 | Depends on the brand. |
If you're testing a new filter, take the water before and after the filter, and the difference in readings will show the actual effectiveness of the cartridge, for example, if you have 300 ppm inlet and 280 ppm outlet, then the filter is almost dead or exhausted.
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When measuring water from a reverse osmosis filter, wait 2-3 minutes after the tap is turned on to drain the water that has stagnated in the membrane. The first portions may have elevated TDS.
Checking the effectiveness of filters and cleaning systems
One of the main applications of the Xiaomi TDS Pen is monitoring the state of filter systems, which is especially important for owners of reverse osmosis systems, where a decrease in the quality of the membrane immediately affects the growth of ppm readings. Regular measurements allow you to change cartridges on time without overpaying or risking the quality of water.
There is a concept of "purification degree", which is calculated as the ratio of TDS of purified water to TDS of the original, it is considered good cleaning when the rate drops by 10 or more times, if the drop is slight, you need to check the tightness of the system or replace the filter elements.
- 🔍 Check the water from the storage tank of osmosis - there the indicator should be minimal.
- 🔍 Compare the readings with water passed through the mineralizer (if any), as it is artificially saturated with salts.
- 🔍 Control the water in Xiaomi humidifiers – if you exceed 100 ppm, white plaque can appear on furniture.
⚠️ Note: If after replacing cartridges in the reverse osmosis system, the indicator TDS never fell 20-30 Check the correct installation of the membrane and the tightness of the joints.
And the tester can also measure the quality of bottled water from different brands, and often expensive water has the same value as cheap water, or worse, and Mi Tester helps you choose the best choice for drinking and cooking based on facts, not advertising.
Caring for the device and replacing the battery
For long-term service, it is important to properly care for the measuring electrodes. After each use, rinse the probe with clean water (preferably distilled or one that has already been tested) and dry with a soft cloth. The remaining salts can curl and interfere with the next measurement.
Keep the device in a protective cap, in a dry place, protected from direct sunlight and extreme temperatures. Despite the moisture-proof housing, prolonged exposure to aggressive environments can damage the display or buttons.
How to replace the battery in Xiaomi TDS Pen?
When the battery icon appears on the screen or the readings become unstable, it's time to replace the battery. Use a standard CR2032 battery. The replacement procedure takes less than a minute and requires no special tools other than a coin or a flat lid screwdriver.
Frequent errors and troubleshooting
Users often experience a situation where readings are jumping or seem counterintuitive. One common mistake is measuring hot water. Although the device has temperature compensation, it is designed for the household range. Boiling water can damage the sensor or give incorrect results due to changes in the structure of dissolved substances.
Another mistake is touching the electrodes with your fingers, and the fatty film on your skin changes conductivity, and if you accidentally touch the probe, make sure to wipe it with an alcohol wipe or clean water before your next measurement, and don't use the tester in heavily chlorinated pool water without washing it thoroughly.
- 🚫 Do not use abrasives to clean electrodes.
- 🚫 Do not leave the device in water longer than required for measurement.
- 🚫 Do not try to disassemble the case if the device is warranty.
⚠️ Warning: If the device shows a value of "0" in tap water or "9999", this may indicate a sensor malfunction or a complete discharge of the battery.
Sometimes users confuse TDS with water hardness. These are different parameters, albeit correlated. TDS shows the total amount of impurities, and the hardness is only calcium and magnesium salts. For Xiaomi humidifiers, TDS is important, since any plaque (not only calcium) clogs the membranes.
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The Xiaomi TDS Pen is a great tool for quick water quality assessment, but it doesn’t replace a full lab analysis if you have a suspicion of bacterial or chemical contamination with specific substances.