The Combo Waterproof Tester takes highly accurate readings of temperature, pH, EC and TDS. The unit is protected by a strong plastic waterproof casing, and comes equipped with a replaceable pH electrode, salt-resistant stainless steel EC/TDS and temperature probes, electrode replacement tools to make maintenance simple, batteries and a self-check feature. A low-battery alert ensures proper functioning and the unit also automatically notifies users when to take and when to freeze the reading for accurate measurements; this tester also features automatic temperature compensation. EC/TDS calibration is 1-point automatic, and pH is 1 or 2-point with two sets of memorized buffers; pH 4.01, 7.01 and 10.01 or 4.01, 8.68 and 9.18. The Combo Waterproof Tester reads EC with a range of 0-3999 µS/cm and resolution of 1µS/cm, TDS with a range of 0-2000ppm and resolution of 1 ppm, pH with a range of 0.00-14.00 and resolution of 0.01, and temperature with a range of 0.0°-60.0°C and resolution of 0.1°C. or 32.0°-140°F and resolution of 0.1°F. The combination of quality, features and portability makes this tester a great choice.