This tester provides a fast and dependable way to measure the Total Dissolved Solids in your water samples. Operating and routine maintenance is easy. A press of the single button, at the top of the meter, powers it on. Press and hold the button, for a few seconds, to automatically enter the 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 is managed by onboard power microprocessor, which automatically turns meter off after 5 minutes of non use