How to use it TDS-Xiaomi tester: full instructions with measurement examples

What is it? TDS-Tester and why you need it in the home

If you have ever thought about the quality of water from the tap, filter or bottled water, then TDS-Xiaomi's tester will be your indispensable assistant, and this compact device measures Total Dissolved Solids, the concentration of salts, minerals and metals dissolved in water, expressed in ppm (parts per million, parts per million). The higher the indicator, the “harder” the water and potentially more harmful to health or household appliances.

Xiaomi has two popular models: Mi TDS Pen (wireless with Bluetooth) and ClearGrass TDS-3 (And both of these devices are conductometric -- they measure the electrical conductivity of water, which is directly related to the amount of dissolved matter. But how do you interpret the results? TDS 500 ppm is considered unfit for drinking by the standards. WHO, A value above 1000 ppm may indicate serious contamination by metals or salts.

In this article, we will discuss:

• 🔍 How to prepare the tester for first use (including calibration).
• 💧 Step-by-step measurement instructions TDS different types of water.
• 📊 Table of norms TDS for drinking, filtered and technical water.
• ⚠️ Common Mistakes That Write Results (and How to Avoid Them).

Package and appearance: what goes into the box

Before the first inclusion, check the complete set of your TDS-Xiaomi tester. The standard set includes:

• 📱 The device itself (depending on the model - with a display or LED indicators).
• 🔋 Battery CR2032 (mi TDS Pen or 2×AAA (at ClearGrass TDS-3).
• 📄 Brief instruction in Chinese/English (Russian version is not usually available).
• 🧪 Calibration solution (if you buy an extended set).

On the body of the device are located:

• Electrodes (metal contacts in the lower part) - they can not be touched with your hands, so as not to distort the measurements.
• The power button (sometimes combined with the calibration button, as in ClearGrass) TDS-3).
• Display (in Mi) TDS Pen — OLED, in budget models - LCD screen).
• Charge indicator (in models with Bluetooth).

Notice the protective cap, which protects the electrodes from damage. If the cap is not included (as some clones do), keep the tester in a dry place wrapped in soft cloth.

Preparation for first use: calibration and verification

Before measuring, the Xiaomi tester needs to be calibrated. Without this procedure, the readings can differ from the real ones by 10-15%. This step is often missed in the instructions, but it is critical for accuracy.

For calibration, you will need a standard solution with a known TDS (If there is no solution, distilled water can be used (TDS ≈ 0 ppm) or bottled water with the labeled composition (e.g., BORJOMI has TDS ~600 ppm).

Step-by-step calibration:

1. Wash the tester electrodes in clean water and wipe with a napkin.
2. Immerse the device in a calibration solution (or distilled water).
3. Hold the switch on 5-10 seconds until the screen does not appear the inscription. CAL or SET.
4. Wait for the stabilization of the readings and confirm the calibration with a short press.

If the tester shows an error ERR or ---, It could mean:

• 🔋 Discharged battery (replace the power supply).
• 💦 Contaminated electrodes (wipe them with a soft cloth with a drop of vinegar).
• 🌡️ Water temperature above 50°C (cool the sample).

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To check the accuracy of the tester after calibration, measure TDS bottled water with known composition (for example, "Essentuki» — ~1000 ppm) and compare with the label.

How to measure correctly TDS: step-by-step

Now let’s move on to the most important thing: the measurement. TDS. The algorithm is simple, but there are nuances that affect the result.

Step 1: Preparation of a water sample

• 🚰 For tap water: let it stand for 2-3 minutes to chlorine escape.
• 💧 For filtered water: the first 50–100 ml of salt (they may contain salts stored in the filter).
• ❄️ For melted or boiled water: cool to room temperature (20–25)°C).

Step 2. Immersion of the tester

Lower the electrodes into water to a depth of 2-3 cm (without touching the bottom or walls of the tank!). You don't need to mix the water - this can create air bubbles that distort the readings. Keep the tester still for 10-15 seconds until the value on the screen stabilizes.

Step 3: Reading the result

The screen will show the value in ppm.

• 25 ppm – ideal water (distilled or after reverse osmosis).
• 150-250 ppm is the best for drinking.
• 500+ ppm – requires additional cleaning.

Step 4: Interpretation of the results

Compare your data with the table of norms:

Synchronization with the phone: the possibilities of Mi TDS Pen

Model Mi TDS Pen supports smartphone connectivity via Bluetooth and the Mi Home app (or Zepp Life for the global version:

• 📲 Keeping the history of measurements by date and time.
• 📊 Schedule changes TDS Dynamically (useful for filter monitoring).
• 🔔 Set up notifications when exceeding thresholds.

How to connect the tester to the phone:

1. Install the Mi Home app (App Store/Google Play).
2. Turn on Bluetooth on your smartphone and tester (hold the 3 second button).
3. In the app, click Add Device → Household appliances → TDS-metre.
4. Confirm the pairing and wait for the data to synchronize.

In the application settings, you can:

• 🔄 Turn on auto-disconnect the tester after 2 minutes of inactivity.
• 🌡️ Activate temperature compensation (ATC) for accurate measurements in hot water.
• 📤 Export data to CSV for analysis in Excel.

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Synchronization with the phone is useful for long-term monitoring, but for one-time measurements, the tester itself is enough - Bluetooth increases battery consumption.

Common Mistakes and How to Avoid Them

Even with a calibrated tester, you can get the wrong data.

⚠️ Attention: Don't measure TDS watery°C, this will cause false overstatement because of the increased electrical conductivity when you heat it.

Mistake 1: Dirty electrodes

Plaque from hard water or greasy finger marks create additional resistance.

• Wipe the electrodes with a cotton swab soaked in 9% vinegar or citric acid.
• Do not use abrasives (sandpaper, metal brushes) - they will damage the coating.

Mistake 2: Improper immersion

If the electrodes touch the walls or bottom of the tank, the tester can show ERR Use a glass with a diameter of at least 5 cm and immerse the tester strictly vertically.

Mistake 3: Ignoring the temperature

Budget models (e.g. ClearGrass) TDS-3) They do not have automatic temperature compensation (ATC). When measuring cold water (below 15)°(C) their testimony will be understated by 10-20:

• Heat the water to 20-25.°C before measuring.
• Or use the correction factor: the real TDS = testimony × 1.02^(20–t, where t is the water temperature.

⚠️ Note: If the tester after immersion in water shows --- or OL, This means exceeding the upper limit of measurement (usually 2000 ppm), dilute the sample with distilled water in a ratio of 1:1 and repeat the measurement.

Practical examples: what to do with the data

Let's say you measured. TDS From different sources?

Example 1: Tap water 450 ppm

This is above the normal drinking rate (optimally up to 300 ppm).

• 🧂 High calcium and magnesium content (hard water).
• 🔧 Worn-out pipes (rust, lead).
• 🏭 Industrial pollution (nitrates, sulphates).

Solution: Install a reverse osmosis filter (reduces) TDS up to 10–50 ppm) or ion exchange filter (softens water).

Example 2: Filtered water - 200 ppm

If you had 450 ppm before filtration and 200 ppm after filtration, your filter works, but it doesn't remove the salts completely. It might be time to replace the cartridge (carbon filters last 2-3 months).

Example 3: Water from the well - 800 ppm

This high rate may indicate:

• 🌊 Seawater penetration (if the well is near the coast).
• 🚜 Pesticides or fertilizers from agricultural runoff.
• 🪨 Washing minerals from the soil (limestone, gypsum).

Solution: Donate water for a full chemical analysis to the laboratory — TDS-The tester does not show specific contaminants.

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If after boiling TDS water increased (for example, from 300 to 350 ppm), this is normal: when heated, some of the salts precipitate, but the total concentration of dissolved substances can increase due to the evaporation of water.

FAQ: Answers to Frequent Questions