There are two principal methods of measuring total dissolved solids: gravimetic and conductivity. The standard method is gravimetric, which is considered the most accurate and involves evaporating the sample to dryness at 103 °C, then to 180 °C to remove any occluded water, (water molecules trapped in mineral  matrix), then weighing it with a precision analytical balance (normally capable of 0.0001 gram accuracy). This method is generally considered best, although it is
slow and has inaccuracies from low-boiling-point chemicals which evaporate with the water.

TDS of water is directly related to the conductivity of dissolved ionized solids in the water. Ions from the dissolved solids create the ability for water to conduct an electrical current, which is measured by the IC Controls 210-C(TDS) analyzer, and immediately displayed as sodium chloride ppm or mg/L or µS/cm conductivity. When periodically standardized with IC Controls TDS standards or by laboratory gravimetric TDS measurement, TDS analyzers based on conductivity provide a quick accurate value of the TDS.

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