1, pH calibration Immerse the pH electrode in a mixed phosphate standard buffer solution with a pH value of 686 (25C) 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 phosphophthalate pH4.01 or borax standard buffer solution pH9.18 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 very important to the fishDifferent fish have different requirements for the PH of the water PH : 0.00 ~ 14.00 The acid-base reaction of water directl affects human health Automatic Temperature Compensation: 0 Celsius -50 Celsius Battery Type: 3X1.5V(AG13) Environment: RH less than 95% Dimensions(mm): 221 x 51mm Wide ApplicationSuitable 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.