JP2786288B

Proposed is an electrochemical probe for determining the air/fuel ratio in exhaust gases from internal combustion engines, both in the fuel-low and in the fuel-rich zone. The probe has a sensor element with an electrochemical oxygen concentration cell and an oxygen pumping cell with a solid electrolyte. The sensor element is housed in a casing which can be inserted into the exhaust pipe in such a way that the electrodes of the oxygen concentration cell and the oxygen pumping cell are outside the exhaust pipe. The atmosphere can enter via openings in the casing and the exhaust gases via a diffusion gap. The sensor element is of particularly simple construction, free oxygen being available to the oxygen pumping cell both in the low and the rich lambda region. The oxygen pumping cell electrodes can be made large, thus making only relatively small current densities necessary. Overcooling of the sensor element in the region of the electrodes by cool exhaust gas (measurement gas) is avoided.