The Milwaukee MC810 pH/TDS/temperature meter automatically and permanently monitors and displays pH/TDS/temp values. Simply calibrate the parameters and let the MC810 do the rest. The Milwaukee MC810 pH/TDS/Temperature Meter is preferred by people who want to know what the pH, temperature and TDS values are around the clock. TDS = Total Dissolved Solids: stands for the total value of dissolved (conductive) solids in the water, for example minerals or salts.Milwaukee digital pH/TDS/Temperature Monitor MC810+ fast easy to read current results with 3 large digital BACKLIT LCD readouts+ accurate to0.2 pH (0.0 pH to 12.0 pH)+ accurate 2% Full Scale TDS+ external Switch atop the unit converts EC conductivity to TDS (ppm) using 0.5 or 0.7 conversion factor+ simple two-point pH calibration and one point TDS, for increased accuracy with manual trimmers for easy adjustment+ gel-filled, double junction MA911B/2 (included) lab grade pH electrode for low maintenance and high performance+ 6.5 fe