Excellent meter, very accurate and durable PH pen have function, not need any kind of screwdrivers to calibrate the pH pen tester. Digital tester and PH tester both have the function of ATC, the measuring data won't be influenced by temperature. Such as hydroponics and gardening, pools and spas, aquariums and reef tanks, water ionizers, Water Filter. drinking water and more. saves measurements for convenient reading and recording Size: 15 x 3 x 1.5 cm Measuring pH Range: 0.0 - 14.0 pH Resolution: 0.1 pH Accuracy: 0.1 pH (20 C), 0.2 pH Operating Temperature: 0 - 50 C (32 - 122 F) Calibration: manual,1 point Please calibrate with the buffer solution before use. 3 x AG 13 button cell batteries(not included ) PH operation steps: 1. Remove the protective cover. 2. Clean the electrode of the pH meter with distilled water first. And wipe the electrode dry with filter paper. 3. Turn on the switch located on the battery compartment. 4. Insert the pH meter into the liquid to be measured until the liquid is immersed in the "immersion line", and conditions permit, the solution can be immersed slightly above the "immersion line". 5. Stir the solution gently and wait for about two minutes. Read the displayed value. 6. Finished use. Clean the electrode. Turn off the switch. Put on a protective cover. PH meter calibrator: the pH standard solid substance. It can be used after opening the package and adding water. It is suitable for the calibration of any type of acidity meter. Two kinds of specifications are pH 4.00 pH 6.86 Dear friends, please note that the PH pen probe is a glass product, which is fragile. Please do not bump it with anything. Once it is damaged, it cannot be replaced. Be sure to protect the probe. Use absorbent paper to gently absorb the water on the probe. And can be. Instructions for use of calibration powder for pH meter: There are two specifisaves measurements for convenient reading and recording. Such as hydroponics and gardening, pools and spas, aquariums and reef tanks, water ionizers, Water Filter. drinking water and more. Digital tester and PH tester both have the function of ATC, the measuring data won't be influenced by temperature. PH pen have function, not need any kind of screwdrivers to calibrate the pH pen tester. Excellent meter, very accurate and durable.