Specifications: Measuring range: 0.00-14.00 pH Resolution: 0.01 pH Accuracy: 0.05 pH Power supply: 2 x 1.5V LR44 batteries (operates for more than 500 hours) Working temperature: 0C to 55C Automatic temperature compensation: 0C to 50C pH meter calibration methods: 1. Dissolve one packet of calibration powder (pH 6.86) in 250 ml of water and mix gently. Insert the probe into the solution to measure the pH value. If the display reads 6.8, the meter is properly calibrated. 2. If the reading deviates from 6.8, use a small screwdriver to adjust the calibration potentiometer (located under the cover) until the display matches the known value of the buffer solution at room temperature. 3. Do not adjust the calibration when the probe is out of water. Note: Measurements are taken manually; please allow for a 1-19 cm measurement variation. Due to differences in lighting and screen displays, colors may vary slightly. Actual product color may differ.