An oxygen sensor configured for electrochemical determination of a concentration of dissolved oxygen in a liquid medium, said oxygen sensor comprises: a working electrode (WE) configured to be in contact with said liquid medium; a reference electrode (RE) configured to be in contact with said liquid medium and having i) a surface area that is equal to or larger than a surface area of said working electrode (WE), and ii) a surface made of Ag/AgCI, wherein said oxygen sensor does not comprise any dedicated counter electrode; a retaining circuitry configured to temporarily retain a floating voltage between said working electrode (WE) and said reference electrode (RE); a measurement voltage circuitry comprising a voltage source (VS) configured to apply a measurement voltage between said working electrode (WE) and said reference electrode (RE) during a first measurement period causing dissolved oxygen in said liquid medium to react by reduction at a surface of said working electrode (WE) to produce an evoked current into said working electrode (WE); a floating voltage circuitry configured to apply a voltage between said working electrode (WE) and said reference electrode (RE) equal to said temporarily retained floating voltage during a second measurement period immediately following and of an equal duration as said first measurement period to produce a current out from said working electrode (WE); and a generating circuitry configured to generate a signal representative of said concentration of dissolved oxygen in said liquid medium based on a measured net charge to said working electrode (WE) equal to a sum of a charge transferred to said working electrode (WE) during at least a last part of said first measurement period and a charge transferred to said working electrode (WE) during at least a last part of said second measurement period. a working electrode (WE) configured to be in contact with said liquid medium; a reference electrode (RE) configured to be in contact with said liquid medium and having i) a surface area that is equal to or larger than a surface area of said working electrode (WE), and ii) a surface made of Ag/AgCI, wherein said oxygen sensor does not comprise any dedicated counter electrode; a retaining circuitry configured to temporarily retain a floating voltage between said working electrode (WE) and said reference electrode (RE); a measurement voltage circuitry comprising a voltage source (VS) configured to apply a measurement voltage between said working electrode (WE) and said reference electrode (RE) during a first measurement period causing dissolved oxygen in said liquid medium to react by reduction at a surface of said working electrode (WE) to produce an evoked current into said working electrode (WE); a floating voltage circuitry configured to apply a voltage between said working electrode (WE) and said reference electrode (RE) equal to said temporarily retained floating voltage during a second measurement period immediately following and of an equal duration as said first measurement period to produce a current out from said working electrode (WE); and a generating circuitry configured to generate a signal representative of said concentration of dissolved oxygen in said liquid medium based on a measured net charge to said working electrode (WE) equal to a sum of a charge transferred to said working electrode (WE) during at least a last part of said first measurement period and a charge transferred to said working electrode (WE) during at least a last part of said second measurement period. <EOS>