Simply press "ON", It only takes a few seconds for your result to appear on LED screen, and accurate measurement and clear display. Backlights function ensures you can use the product in a dimly lit working environment. High-accuracy electrode chip and lab quality glass probe ensure accurate and fast response. Measures 0 ~ 14 pH range with a high 0.01 pH resolution. Press "CAL" for 5 seconds to enter the calibration mode, press in turn to select the powders corresponding to 6.86, 4.01, and 9.18 to complete the calibration The pH tester has ATC function, so it can be adjusted according to water temperature to give pH readings almost instantly. PH Meters to measure the pH in your pool and spa; Ideal for residential or commercial use, drinking water, aquarium, liquid food, brewing, RO system and hydroponics. Measurement range 0-14, accuracy 0.01