Specifications: Measure range: 0.00 - 14.00 PHResolution: 0.01PHAccuracy: Â0.01 PH (at 25) Power Supply: 2*1.5V (LR44 Included) Operating Temperature: 0 - 80 (32 - 176 Fahrenheit) Dimension: 155mm* 31mm * 18mm / 6.10 Weight: 50g / 1.76oz Calibration: 1. Turn on the pH meter. 2. Dissolve each buffer solution in 250 ml of distilled water. 3. Immerse the electrode into the pH 6.86 solution (under the temperature of 25℃). 4. Press the CAL(calibration) button for 5 seconds and release - Display screen will start flashing - Wait for it until the display screen stops flashing - Rinse the electrode with distilled water and make it dry with filter paper. 5. Repeat the above steps with 4.01 pH buffer powder and 9.18 pH buffer powder. Note:Calibration is required in the following conditions.- Lengthy periods of inactivity- Very frequent use- The testing accuracy requirement is very high- The key was pushed and the electrode was exposed to air for an extended period of time.