Temperature compensated polarographic oxygen gas sensor and sensing system, particularly for automotive application

Temperature and aging compensated polarographic sensing system to determine the oxygen content of gases, especially exhaust gases from an internal combustion engine comprising

• a single solid electrolyte body (1);
• a first electrode forming an anode electrode (3), applied to a first surface portion of said body, and exposed to the gases;
• a second electrode forming a cathode electrode (2) applied to a second surface portion of the body spaced from said first surface portion by a first electrolyte body portion (1a);
• voltage source means (7) furnishing a voltage, having one terminal (-) connected to one (2) of the electrodes, and second terminal (+) connected to the other one (3) of the electrodes (2, 3);
• means (6) forming a diffusion barrier controlling access of oxygen molecules to the cathode electrode (2);
• current sensing means (8) measuring the current in an oxygen ion sensing system formed by the voltage source means (7), the anode electrode (3), the solid electrolyte body between the first and the second surface portions of the solid electrolyte body and the cathode electrode (2) and providing an output indication of limit current flow as a function of diffusion of oxygen molecules through said diffusion barrier,
• and means for rendering the current independent of aging effects and temperature, comprising
• a third electrode (4) positioned on a third surface portion of said solid electrolyte body (1) spaced from said one of said electrodes by a second body portion (1b) and being serially connected between the other terminal (+) of the voltage source and said other one (3) of the electrodes (2, 3), said further electrode (4) and said second body portion (1b) of said solid electrolyte body (1) forming an oxygen ion conductive ohmic resistance which is serially connected between the cathode and anode electrodes (2, 3).