Gas sensor

摘要

A gas sensor assumes a laminate structure composed of thin sheets of solid electrolyte and includes a cavity portion 21 and an oxygen concentration cell 5. The oxygen concentration in the cavity portion 21 is held constant. The oxygen concentration cell 5 includes an active electrode 12 having a relatively high catalytic capability with respect to NOx or combustible gas and an inner common electrode 13/15 (serving as an inactive electrode and an oxygen-concentration-sensing electrode) having a relatively low catalytic capability with respect to NOx or combustible gas. The oxygen concentration cell 5 is disposed so as to be exposed to the interior of the cavity portion 21. The concentration of NOx or combustible gas is determined on the basis of an electromotive force (of the order of mV) generated between the active electrode 12 and the inner common electrode 13/15 by the concentration cell effect. <IMAGE> <IMAGE>