The invention concerns a polarographic sensor for the determination of certain components in the exhaust from internal combustion engines in order to control the air/fuel ratio. The sensor can be used in exhaust gases from both fuel-rich and fuel-poor mixtures. It includes a first pumping cell (10), whose cathode (12) has a diffusion barrier (14), and a second pumping cell (20) whose anode (24) also has a diffusion barrier (26). Suitable circuitry enables the limiting current delivered by one of the two pumping cells to be used as a signal for control of the fuel/air mixture. The invention also concerns the use of the sensor in the control of the ratio of the components in the fuel/air mixture fed to an internal combustion engine.
