When the test pen leaves the factory, it has been calibrated and can be used directly. The following conditions must be re-calibrated:
1. It has been used (or placed) for a long time after calibration;
2. Electrodes are used very frequently;
3. The measurement accuracy requirements are relatively high;
4. When doing calibration, do not reuse the calibration buffer;
5. When there are white crystals on the tip of the pen, this is a normal phenomenon, please do not be nervous, you can soak it in water for a period of time;
6. Drop a few drops of preservation solution or calibration buffer in the pen sleeve. Do not use distilled water or pure water to soak or store the test pen;
7. There may be small bubbles in the sensitive bulb of the glass electrode of the test pen, which will affect the normal measurement of the electrode. The electrode should be shaken during use to make the bubbles run out of the sensitive bulb;
8. The glass electrode is easy to break, so be careful when using it;
9. If the displayed value is fuzzy or not displayed or the displayed value is much higher or lower than the real pH value of the solution, the battery should be replaced.
