How to use calibrationPress CAL for 5 seconds to enter the calibration mode, press in turn to select the powders corresponding to 6.86, 4, and 9.18 to complete the calibration. Mini SizeThe mini size ph meter we designed allows you to easily put it in your pocket, so you can take measurements anytime, anywhere. It can help you test it whether you take it to the pool, on a trip, to the beach or camping. Family EssentialsAs a tool to improve the quality of life. Can be used to test drinking water, swimming pools, PH balance in aquarium, RO system, spa or hydroponics. Basically all the environments that need to test PH value can use this tester to get accurate data. Easy to useturn on the switch,put the probe into the water and stir (make the small glass ball fully contact the liquid) and the value can be read when the value is stable. Automatic temperature compensationThere is no need to care about the temperature of the liquid being measured. The PH meter has an automatic temperature compensation function, which can be adjusted according to the water temperature and water quality.