Instructions for use of PH calibration powder: Calibration powder: pH standard solid substance. It can be used after adding water. Suitable for the calibration of any type of ph meter. Each package can prepare 250ML standard solution. (Be sure to add water according to the required ratio, otherwise it will affect the accuracy of the calibration and increase the error) Precautions: Please note that the PH pen probe is a glass product and is a fragile product. Please do not collide with things. Once the damage is not replaceable, you must protect the probe. After use, use absorbent paper to gently absorb the water on the probe. Matters needing attention: PH meter has been calibrated before delivery, the buyer does not need to re-calibrate after receiving the goods In the following cases, the PH meter must be re-calibrated: 1. Has been used for a long time after calibration; 2. Special electrode use Frequently; 3. The measurement accuracy requirements are relatively high. Battery installation: If the backlight brightness drops significantly or the display value is blurred, the battery should be replaced. When replacing the battery, just pull out the battery compartment and replace it. NoteThe polarity of the battery. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Sold by-YJL official store