HM Digital ORP-200 Waterproof ORP Meter, -999 to +1000 mV ORP Range, 1 mV Resolution, +/- 0.5% Readout Accuracy Measures Oxidation Reduction Potential (Redox) and Temperature Auto-ranging calibration with digital fine tuning Includes storage solution in a sponge embedded in a clear cap Waterproof housing (IP-67 rating) Simultaneous temperature display The ORP Metermeasures oxidation reduction potential (Redox) and temperature The ORP-200 meter has anauto-ranging calibration with digital fine tuning This Waterproof ORP Meterincludes storage solutionin a sponge embedded in a clear cap