The TDS-3 is a handheld meter designed to measure Total Dissolved Solids (TDS) in water. It also includes a built-in thermometer to measure water temperature. Key features include a hold function for saving readings, auto-off for battery conservation, and a carrying case. The meter measures TDS from 0 to 9990 ppm with a resolution of 1 ppm for values up to 999 ppm and 10 ppm for values above 1000 ppm, and temperature from 0 to 80°C.