Applying a potential difference pd (between 700 and 1200 mV), leads to electrolysis: the platinum (or gold) electrode acts as the cathode (reduction) and the silver electrode as an anode (oxidation). The reactions are:

With a microampere meter, the cathodic current I_C is measured. It gives the diffusion limit for the reduction reaction of O₂ to HO^- or H₂O I_c^lim. The intensity of this current is directly proportional to the diffusion rate of O₂ towards the cathode and the dissolved oxygen concentration [O₂]:

where F is the Faraday constant, D_m is the diffusion coefficient of O₂ through the membrane, K_m is the solubility product constant for O₂ in the membrane, P_m is the membrane permeability which is D_mK_m, S is surface area of the electrode and e is the thickness of the membrane.

Dioxygen concentrations in the electrolyte solution and outside the cell are in equilibrium: if the dioxygen concentration in the solution increases, then that of the electrolyte solution increases as well. This makes it possible to determine O2 concentration by measuring the diffusion-limited current of the reduction reaction.