The Primo TDS tester provides a fast and dependable way to measure the total dissolved solids in your water samples. It is ideally suited for the rigorous demands of water quality professionals, who will appreciate the easy-to-read LCD when demonstrating the before and after results of conditioning and filtration systems. Temperature is compensated automatically to ensure the readings are consistent to the standard or reference temperature. Primo TDS uses a single button at the top of the meter. Press it once and the meter is powered and ready for use. Press and hold the button for a few seconds and Primo automatically enters calibration mode. Simply open a sachet of the calibration solution, dip the probe and within seconds the meter recognizes the calibration solution and calibrates itself! Maximum battery life with auto turn off after 5 minutes.