Patent ID: 7258772

Claim:
An oxygen sensor comprising: a solid electrolyte layer having an oxygen ion conductivity; a pair of pumping electrodes formed to face each other with said solid electrolyte layer therebetween; a reference electrode formed to face one of said pair of pumping electrodes with said solid electrolyte layer therebetween; an oxygen supply power source that applies, between said reference electrode and said one pumping electrode, a voltage for supplying oxygen to said reference electrode; a dense layer covering said reference electrode, and one and the other outputs, the one being configured to output an electromotive force generated between the one pumping electrode and the reference electrode as a first detection signal first, and the other being configured to output a limiting current flowing between the pair of pumping electrodes as a second detection signal, wherein a gas diffusion layer is formed annularly on a periphery of a rod shaped base; and the solid electrolyte layer, the dense layer, the pair of pumping electrodes and the reference electrode are formed annularly on a periphery of the gas diffusion layer.