Mettler Toledo Thornton’s new Water Calculator provides you with the ability to do simple conductivity, resistivity and flow calculations and conversions using your iPhone, iPod touch or iPad. This app calculates: Conductivity, Resistivity, and Total Dissolved Solids (TDS) measurements in water including unit conversions. Temperature conversion between °C and °F. Displays the temperature compensated resistivity for ultra pure water at a specified temperature. Flow rate to flow velocity.