... .pH electrode included Features:pH 6.86, pH 4.01 or pH 9.18, 3 points calibrationAuto calibration for pH 4.01, pH 6.86 or pH ... the desired valueAuto power off without operation in 20 mins.Available for wide applications, such as aquarium, beverage, fish hatcheries, food ... control, school & colleges, swimming pools, water conditions . PT-6022 digital PH meter, Pen type digital pH meter