HM Digital Handheld TDS Tester Model TDS-3 Ideal for commercial use. Includes a carrying case with belt clip. Highly efficient and accurate due to its advanced microprocessor technology. Hold Function: saves measurements for convenient reading and recording. Auto-off function: the meter shuts off automatically after 10 minutes of non-use to conserve batteries. Measurement Range: 0-9990 ppm. Built-in digital thermometer Display: large and easy-to-read LCD screen. Factory Calibrated: our meters are calibrated with a 342 ppm NaCl solution. Meters can be recalibrated with a mini-screwdriver. Also available in "x 10" mode: reads in increments only of 10 ppm (0-9990 ppm). 3 year warranty.