Why Measure Conductivity?

Fresh water from municipal water systems or private wells contains a certain amount of dissolved solids. Some of these solids break down into electrically charged ions in their aqueous state. The classic physics lab example is common table salt (NaCl), which reduces to a positive sodium ion (Na+) and a negative chlorine ion (Cl-) in solution with water. The presence of these ions allows the solution to conduct electricity - the higher the concentration of ions, the greater the conductivity. Thus, a measurement of the solutionâ s conductivity gives a reliable clue to the concentration of dissolved solids in cooling tower water, boiler feedwater, process rinse water, or even our cool, refreshing summer drink. Conductivity is measured in Siemens (S) per centimeter (the inverse of Ohms per centimeter), and is the ratio of induced current to applied voltage across a one centimeter gap. The â per centimeterâ portion is often implied rather than stated.