Small enough to fit in your pocket, the Oakton WD-35634-60 PCTSTestr 5 multi-parameter tester is ideal for measuring pH, conductivity, TDS, and salinity parameters as well as temperature. The large display provides easy viewing of measurements and features a two-color backlight - blue for measurement and green for calibration mode. A replaceable single-junction sensor saves you money by reusing the tester body.|Additional features include automatic temperature compensation (ATC), hold function to lock in measurements, self-diagnostic error message, and status icons for measurement stability and low battery voltage. The IP67-rated housing features an easy-to-grip design and floats if accidentally dropped in water when sensor cap is on. Powered by 4 AAA batteries, the tester can operate up to 400 hours continuously. To conserve power, the unit will auto power-off after 8 minutes of non-use.