... Water quality control system 2. Backlight 3. Tds range:0~9999ppm 4. Easy to operate 5. Portable style TDS control ... you can test the quality of various water in the following situations: water purification applications, wastewater regulation, aquaculture, ... boilers & cooling towers, food processing, physics & chemistry teaching, water treatment, cosmetics, wine, home, office, travelling and more. ...