Pocket Portable Digital pH Meter Tester Water Quality Testing for Swimming Pool Aquarium Condition: Item Type: pH Meter Material: Plastic Working Temperature: 0-50℃ RH＜95% (32-122℉) Measuring pH Range: 0.0-14.0pH Resolution: 0.1pH Accuracy: ±0.2pH (at 20℃) / ±0.2pH Battery: 4 x 1.5V Button Battery (Not Included) Product Size: Approx. 3.1 x 1.6 x 15 cm / 1.2 x 0.6 x 5.9 in Weight: Approx. 120g / 4.2oz Operating Steps: 1. Remove the protective cover. 2. Firstly, the electrode of the pH meter should be cleaned with distilled water, and wipe the electrode with filter paper. 3. Turn on the power button located on the battery compartment. 4. Insert the pH meter into the liquid to be measured until the liquid is immersed in the ''immersion line''. If condition allowed, the solution can be immersed slightly above the ''immersion line''. 5. Stir the solution gently and wait for about two minutes, and then read the displayed value. 6. After use, the electrode should be cleaned, turn off the power and put on the protective cover. pH Tester Calibration: 1. Put the pen into the pH6.86 calibration buffer, the height of the buffer solution should not exceed the height of the pen cover, but it must be higher than the electrode. 2. Gently stir the pen in the buffer and let it stand for about 5 seconds. When the reading is stable, stir again and let it stand for about 5 seconds. Repeat several times until the reading is stable and no longer changes. Use a screwdriver to aim the correction button (The small hole on the back), slowly adjust to a reading of 6.86, and then let it stand for about 5 seconds until the reading is stable, that is, the calibration is successful. Note: (Each measurement process needs to be rinsed with tap water). 3. Put the pen into the pH4.0 calibration buffer, the height of the buffer solution should not exceed the height of the pen cover, but it must be higher than the electrode. 4. Gently stir the pen in the buffer and let it stand for about 5 seconds. When the reading is stable, stir again and let it stand for about 5 seconds. Repeat several times until the reading is stable and no longer changes. Use a screwdriver to aim the correction button (The small hole on the back), slowly adjust to a reading of 4.0, and then let it stand for about 5 seconds until the reading is stable, that is, the calibration is successful. pH Tester Maintenance: 1. When there is white crystal on the pen tip, this is normal, don't be nervous, you can soak it in water for a while. 2. Remove the pen cover and turn on the power, it is normal for the digits jumping in the air. 3. Put the pen into the solution to be tested, the height of the solution cannot be higher than the height of the pen cover, but it must be higher than the electrode. 4. Regularly calibrate the PH tester. Generally, it needs to be re-calibrated every three months. 5. After calibration, gently stir the pen in the solution to be tested and let it stand for about 5 seconds. When the reading is stable, stir again and let it stand for about 5 seconds. Repeat several times until the reading is stable and does not change. The reading now is the correct pH. 6. After use, immerse the pen tip electrode in water and wash off the test solution on the electrode. Do not flush the other parts, then cover the pen cover back, and turn off the power.