The Triplett WQ120 waterproof (IP57) PH/Conductivity Pen combines a flat surface pH electrode with a multi-range conductivity cell to measure pH, TDS, Conductivity, Salinity and Temperature. The flat surface electrode for pH can measure solids, semi-solids, and liquids. It simultaneously displays pH, TDS, Conductivity, or Salinity and Temperature and has an analog bargraph for viewing trends. The Triplett WQ120 features ATC (Automatic Temperature Control) that compensates for temperature changes, adjustable TDS compensation ratio, 1-, 2-, or 3-point pH and Conductivity calibration, and a RENEW warning when probe needs cleaning or replacement. Additional features include the ability to store/recall 25 readings, a Hold function that "freezes" the reading on the display, and Auto power off (after 10 minutes) with disable conserves battery life.