The Milwaukee CD600 Total Dissolved Solids (TDS) Pen is designed for hydroponics, aquariums, horticulture, water conditioning and many other applications. The CD600 helps you make sure that your plants are receiving the right amount of nutrient or helps you keep your filters up-to-date and clean for water filtration. Keep TDS in your target range to help your achieve better results.Milwaukee digital TDS Tester CD600+ measures Total Disolved (TDS) direct and with automatic temperature compensation+ ideal range for hydroponics (0 to 1990 ppm)+ units in ppm easily convertable to uS/cm+ factory calibrated with the ability to recalibrate if needed+ automatic Temperature Compensation (ATC)+ 350 hours continuous use (4 x 1.5V batteries included)+ simple one point calibrationtechnical data Milwaukee digital TDS Tester CD600measuring range: 0 to 1990 ppmresolution: 10 ppmaccuracy: +/-2 % Full Scalecalibration: Manual, at 1 point through trimmertemperature Compensation: Automatic from 5 to 50CB