Exhaust gas sensor system

摘要

The present invention provides an apparatus for measuring the concentration of a constituent to be detected in exhaust gas, which apparatus is capable of detecting with a high accuracy the concentration of the constituent to be detected in exhaust gas even though oxygen concentration in the exhaust gas varies. In an exhaust gas sensor 1 for use in the measuring apparatus, exhaust gas is introduced into spaces 15, 16 on both sides of an oxygen concentration cell element 4, and the oxidation catalyst activities of first to third electrodes 11 to 13 are adjusted so that there occurs a difference between the space 15 and the space 16 in the consumption of the constituent to be detected, which consumption is caused by the oxidation of the constituent. Thus a concentration cell electromotive force is generated in the oxygen concentration cell element 4, and an oxygen pump element 3 pumps oxygen into or out of the space 15 so that the electromotive force is held at an target value EC not more than 10 mV. The pump current at this time is taken as the detection output on the constituent to be detected. The strengths of the oxygen concentration cell element 4 and of the oxygen pump element 3 can be increased by the provision of an integrated sintered body in which the elements 4 and 3 are laminated together with the space 15 formed between the first electrode 11 and the second electrode 12. Besides, the accuracy of detecting the constituent to be detected can be improved by the control over the temperature of the oxygen concentration cell element 4 and by the temperature compensation to the pump current. <IMAGE>