Polarographic oxygen concentration sensor and method of determining oxygen content in the exhaust gases of an internal combustion engine

A solid electrolyte is sandwiched between a measuring electrode exposed to the gas and a reference electrode exposed to a reference gas of known oxygen level, and a cover, for example in form of a layer or a cap, is applied over the measuring electrode. To linearize output from the sensor over a wide range of oxygen partial pressure in a gas so that, upon applying a voltage across the electrodes thereof, current flow will be representative of the oxygen concentration in the gas, the cover consists of a material having a predetermined diffusion resistance to oxygen while essentially inhibiting convection of gases to the electrode and limiting the quantity of oxygen reaching the measuring electrode to that value at which any oxygen molecules reaching the measuring electrode will be immediately converted by electrode reaction, thus inhibiting current flow through the sensor due to diffusion of gases and preventing that the current through the sensor will be determined by the activating energy of the charge penetration through the phase separation at the electrode surface.