The TDS Meter is designed to measure TDS (TDS, mg/L), Electrical Conductivity (EC, µS/cm) and Temperature (°C) and Fahrenheit (°C). Total Dissolved Solids (TDS) are the total amount of mobile charged ions (including salts or metals) dissolved in a given volume of water. TDS, which is based on conductivity, is expressed in parts per million (PPM) or milligrams per litre (mg/L). TDS includes inorganic elements present other than pure water molecule (H20) and suspended solids.