Method and system for measuring the oxygen concentration

摘要

A method and a system for measuring the oxygen partial pressure in the exhaust gas of an internal combustion engine is described. A solid-electrolyte sensor tube is used which gives an electrical signal representing the oxygen partial pressure. The internal surface and the external surface of the sensor tube are each exposed to the atmospheric air and to the exhaust gas. If the exhaust gas comes from a gas mixture with an air/fuel ratio in the vicinity of the theoretical value, the electromotive force generated in the sensor tube is detected for emitting a signal and, if the gas mixture has an air/fuel ratio above the theoretical value, a constant voltage is applied between the internal and external surfaces of the sensor tube, and the limiting current flowing in the tube is detected for generating the electrical signal. In this way, a satisfactory measurement can be carried out within a wide range.