Chlorine Sensors

The free chlorine sensor works according to the principle of depolarization of a galvanic element.

The sensor 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. With non-flowing water the electrodes would polarize and interrupt the current flow (hydrogen gas at the platinum electrode, oxide layer at the copper electrode). The constant flow causes small glass balls inside the sensor to circulate and remove any passivation layer from the electrodes. With these stable conditions, the sensor current increases proportionally to the free chlorine surplus.