GLOSSARY: Resistance (Filter)

A Resistance (Filter) is defined as the pressure drop across a filter at a stated flow and under given conditions; generally expressed in millimeters water gauge or PSI, or in SI units as N/m² or Pascals. Resistivity is the reciprocal of conductivity (R=1/C). It is a measure of specific resistance to the flow of electricity. In water, provides an easy mean of continuously measuring the purity of very low Total Dissolved Solids (TDS), or ionic concentration. The fewer the dissolved ions in water, the higher is its resistivity. Resistivity is normally expressed in Megohm-cm and is equivalent to one million ohms of resistance measured between two electrodes one centimeter apart. The theoretical maximum ionic purity of water is 18.3 Megohm-cm at 25°C.