... .LCD indicates both mV value and temp. 2.Data hold function for freezing the desired value. 3.Water proof. 4.Easy ... best linearity and accuracy .Less than 80% RHMicrocomputer circuit, intelligent function, high accuracyPower supply by 1.5 V battery (LR44 ) x ... control, school & colleges, swimming pools, water conditions. PT-8022 ORP meter,Pen type ORP ...