Chlorine Measuring Cells

The measuring cell contains a platinum and a copper electrode. With the sample water acting as the electrolyte, galvanic potential develops between the two electrodes, depending on the electrode material. If the sample water was not moving, the electrodes would polarize and the current flow would gradually be interrupted due to insulation caused by hydrogen ions (gas).

Glass balls inside the cell rotate as they are actuated by the continuous sample water flow, and thus remove the hydrogen gas layer from the electrodes. Starting from this constant basic condition, the cell current increases in proportion to the free chlorine surplus. The current is analyzed by connected amplifiers. The disinfecting efficiency of chlorine strongly depends on the pH value. This is shown in the following dissociation diagram. Consequently, a constant pH value is required for the sample water. Otherwise, the same chlorine content would give different readings.