... the best linearity and accuracy .Less than 80% RHMicrocomputer circuit, intelligent function, high accuracyPower supply by 1.5 V battery (LR44 ... ) x 4 PCsAuto calibration for 0 mV, 500mVBuild in temperature sensor, ATC (auto temperature compensation).Available for wide applications, such as ... control, school & colleges, swimming pools, water conditions. PT-8022 ORP meter,Pen type ORP ...