The ZT-2 Is highly efficient and accurate due to its advanced microprocessor technology, The ZT-2 Tests for inorganic materials commonly found in drinking water, The ZT-2 May be used on all types of water except hot water, The ZT-2 Is an economy model that is ideal for end-users and retail products, The HM Digital ZT-2 has an auto-off function: the meter shuts off automatically after 10 minutes of non-use to conserve batteries, The HM Digital ZT-2 has a measurement range: 0-999 ppm, The ZT-2 has a large and easy-to-read LCD screen, The ZT-2 is factory calibrated with a 342 ppm NaCl solution, Meters can be recalibrated with a mini-screwdriver, The EPA Secondary Regulations recommend a maximum contamination level (MCL) of 500mg/liter (500 parts per million (ppm)) for Total Dissolved Solids, Many water supplies exceed this TDS level, When TDS levels exceed 1000mg/L it is usually considered unfit for human use, After reverse osmosis, distillation, deionization, microfiltration, the TDS level should be less than 50 ppm, Test your incoming water supply and the treated water to determine how much Total Dissolved Solids are being removed from the water, At least 80% of the TDS in your water should be removed, If the TDS rejection is less than 80%, it is time to change your RO membrane, Range: 0 - 999 ppm (mg/L), Resolution: 1 ppm (0-999 ppm), Accuracy: +/- 3%, Conversion Factor: NaCl (avg, 0, 5), Power source: 2 x 1, 5V button cell batteries (included) (357A), Battery life: Approx, 1000 hours of usage, Dimensions: 14 x 2, 3 x 1, 5 cm (5, 5"" x 0, 9"" x 0, 75""), SKU: CWD1877