TDS Water Quality Pen Test. Professional TDS, EC and Temperature Pen. Upgraded with large backlit LCD display for easy reading and auto-lock feature for ease of use Test Drinking Water Meter. To achieve high accuracy, equipped with automatic temperature compensation (ATC) probe made of superior and reliable titanium alloy ensures always accurate readings at different temperatures High Precision Pen Test. TDS stands for total dissolved solids, which are the inorganic salts and organic matter in a liquid. This includes Calcium, Magnesium, Sodium, etc. TDS Meter Water Quality Tester. Features a hold function that saves measurements for convenient reading and recording LCD Display Water Tester. With just the press of a button, the TDS can tell you your water purity level, which will be displayed on the screen in ppm