The Extech EC400 ExStik Waterproof Conductivity, TDS, Salinity, and Temperature Meter is a high accuracy multi-range sensor that measures four parameters (Conductivity, TDS, Salinity and Temperature). Features also include: 6 units of measure, internal memory that stores up to 15 labeled readings for easy recall, adjustable conductivity to TDS ratio factor from 0.4 to 1.0, and self-calibration on power up. 6 selectable units of measurement--mS, mS, ppm, ppt, mg/L and g/L Automatic temperature compensation Automatic self calibration Stores/recalls up to 15 labeled readings Adjustable conductivity to TDS ratio factor from 0.4 to 1.0