... or pH 9.18, 3 points calibrationAuto calibration for pH 4.01, pH 6.86 or pH 9.18.Microcomputer ... circuit, intelligent function, high accuracyPower supply by 1.5 V battery (LR44) x ... beverage, fish hatcheries, food processing, photography, laboratory, quality control, school & colleges, swimming pools, water conditions . PT-6022 digital PH meter, Pen type digital pH meter