The Triplett CD100 Conductivity/TDS/Salinity Pen measures TDS, Conductivity, Salinity and Temperature. The CD100 simultaneously displays conductivity, TDS, or salinity and temperature and has an analog bargraph for viewing trends. The CD100 features ATC (Automatic Temperature Control) that compensates for temperature changes, adjustable TDS compensation ratio, 1-, 2-, or 3-point conductivity calibration, and a RENEW warning when probe needs cleaning or replacement. The CD100 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.