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 getaccurate data. High Accuracyph tester has a sensitive electrode sensor ,simply press "ON", It only takes a few seconds for your result to appear on screen.read accurate pH levels. The included detailed manual will show you how to get the best accurate and stable reading. Automatic Temperature CompensationNo more need to take care about the temperature of testing liquid,as the Ph Meter Has an Auto Temprature Compensation Feature That Adjusts to Water Temperatures and Water Quality.