Patent ID: 7270736

Claim:
A method for determining the pH value of chlorinated water using an electrochemical sensor provided with an electrode system for an electrochemical cell comprising: an electrically conductive substrate ( 10 ); an electrically insulating layer ( 14 ) deposited on the substrate and pierced with a plurality of circular orifices ( 16 ); an electrically conductive layer ( 22 ) deposited in said orifices ( 16 ) in contact with the substrate and on a portion of the insulating layer ( 10 ) that surrounds them, forming a plurality of micro-discs, which form an indicating electrode; and an electrically conductive layer ( 20 ) deposited on the insulating layer ( 14 ), pierced with circular orifices ( 24 ) of larger diameter than that of the micro-discs and arranged such that each orifice ( 24 ) is concentric with a micro-disc, said layer forming a generator electrode; characterized in that it consists in: measuring a first concentration A of hypochlorous acid when the generator electrode is inactive; activating said generator electrode so as to bring the pH value of the water at the micro-discs of the indicating electrode to a sufficient level of acidity; measuring a second concentration B of hypochlorous acid in an acid medium; and determining the pH value from the ratio of said first concentration to said second concentration.