Specification:▲Measuring range: 0.00-14.00PH ▲Resolution: 0.01 pH ▲Accuracy: ± 0.1 pH ▲Operating Temperature: 0-80 ▲Dimension: 153mm x 29mm x 16mm ▲Life expectancy: about 500 hours ▲Relative humidity <95% ▲Digital pH meter with two key: On and off switch + Auto Calibration button ▲Auto- One Touch Automatic Calibration; CAL - Calibration buttonFeature: ▲Large digital display makes it easy to read ▲Pocket sized, handheld pH meter is lightweight, compact, conveniently fits in your pocket or bag and goes anywhere ▲High accuracy ± 0.1 pH ▲With automatic temperature compensation (ATC) feature ▲Easy to set up with the solutions provided,Batteries to power the instrument is included ▲Very uesful tool, necessary for home, aquarium, fishing industry, swimming pool, school laboratory, food and drinks, etcNote: ▲Please do not immerse the meter into the solution over the "warning line", to avoid damage to the circuit board ▲If the "cal'(calibration) button is pressed and electrode exposed to air for a long time,calibration is required Package: ▲1x Digital PH Meter ▲3x PH buffer powder ▲9x Instructions. please clean the electrode with distilled water, then blot the water that covered on the electrode by filter paper. For the calibration method of 6.86 buffer powder, completely put the whole package of 6.86 powder powder into a clean 250 mL of glass beaker, add 250 mL of deionized water to the beaker powder, stir until the powder has completely dissolved, then press one time calibration key, putting the ph tester into the 6.86 solution, shaking the container slowly and calibrating until it stayed in the 6.86 number after waiting for numerical stability, then clean the electrode of ph tester, and blot the solution. Same operation steps about the calibration method of 4.0 buffer powder. Finally, put the ph tester on original glasses to test if the result is accurate or not. As long as the number is in the reasonable range that ups and downs, it can be as a kind of phenomenon. Afterwards you can test the power of hydrogen well.y77hhhhhhh