New THERMO SCIENTIFIC Orion TDS

Several years old, not used.

The standard method of determining TDS (total dissolved solids) is by evaporating the sample to dryness at 180 °C and weighing the residue. Conductivity can be used to estimate TDS. This is done by calculating what concentration of sodium chloride would have the same conductivity as the sample at the same temperature. Thermo Scientific Orion conductivity meters report a sample’s TDS value in mg/L of sodium chloride by comparing the conductivity and temperature of the sample to data stored in the meter’s memory. The stored data was obtained from the International Critical Tables. For temperature values between 5 and 70 °C, and TDS values between 0 and 19,999 mg/L, the displayed TDS value agrees with the International Critical Tables values with an accuracy of 0.87% RSD.