Resistivity instrumentation has served the water purification industry well for many years. A few years ago, as a result of the reliability and endu- rance of this measurement, resistivity instrumentation was almost taken for granted when designing new water systems. It was not uncommon for resistivity instruments to be completely overlooked during the annual (or biannual) plant maintenance programs.
Calibration was never seriously considered or, in some cases, instruments could not even be calibrated in the field. But today, with new technologies and improvements in water purification systems, resistivity instrumentation has become an integral part of a water purification system. Water purification designers are demanding greater reliability, lower costs, easier calibration processes, and improved accuracy.