1. pH calibration: Immerse the pH electrode in a mixed phosphate standard buffer solution with a pH value of 6.86 (25°C) and shake gently. 2. Use a small screwdriver to adjust the calibration potentiometer until the displayed value matches the pH value of the standard buffer solution at the solution temperature. Then wash the electrode of the pH meter with distilled water, and use filter paper to dry the moisture attached to the electrode and its surroundings. 3. Insert the electrode into potassium hydrogen phthalate pH 4.01 or borax standard buffer solution pH 9.18. 4. When the displayed value is stable, the displayed value should be within the allowable error range compared with the pH value of the buffer solution. The pH of the water is important for aquatic life. Different fish have different requirements for water pH. pH range: 0.00 ~ 14.00. The acid-base reaction of water can affect aquatic environments. Automatic Temperature Compensation: 0°C - 50°C Battery Type: 3 x 1.5V (AG13) Environment: RH less than 95% Dimensions (mm): 221 x 51 Wide application: Suitable for water quality testing, aquaculture, farmland irrigation, laboratories, farms, etc. Color: Red Material: Plastic Package Contents: 1 x Digital Acidity Meter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to be slightly different from the real thing. The measurement allowed error is +/- 1-3 cm.