The Sure Test? Pro EC/TDS Pen reads EC, TDS and temperature (?F or ?C) with automatic temperature compensation (ATC) for more reliable conductivity measurements. Auto or manual ranging for EC (uS/mS) and TDS (ppm/ppt). TDS conversion factor is selectable between 400 and 1000. Adjustable calibration values. Waterproof housing (IP65 rated). Comes with 4x LR44 batteries.