How is TDS measured?
TDS is usually measured by weight in terms of milligrams per litre (mg/L) or parts per million (ppm). It can be determined in 2 different ways, either by evaporating a filtered sample to dryness at 180?C in a weighed dish or by using a conductivity meter. TDS measurements determined by conductivity are actually a measure of the conductivity of the sample, i.e., the ability of the water to carry a charge, and not the actual total dissolved solids. This TDS value is then calculated based on the assumption that the primary dissolved minerals are either a combination of NaCl or KCl.
