Abstract: A gas sensor for measuring NOx concentration in measurement gas based on sensor output depending on an amount of the detected oxygen includes an oxygen concentration control part for controlling oxygen concentration in the measurement gas. The oxygen concentration control part allows a control of oxygen concentration in the measurement gas to set at a designated value even after being mounted on an automobile, so that dependency of the sensor output with respect to oxygen concentration can be quantitatively detected. The sensor output for detecting NOx concentration is corrected by estimating an amount of a change accompanying the sensitivity degradation of the sensor output with respect to NOx concentration on the basis of a difference between oxygen output characteristics of the sensor output of an actually-used sensor and oxygen output characteristics of a sensor in the initial state, and correcting the sensor output in accordance with the amount of the change.

Abstract: A sensor for specifying a concentration of a predetermined gas component in a measurement gas on the basis of a current flowing in an electrolyte by decomposition of the predetermined gas component, includes an internal space; a reference gas space; a pumping cell capable of pumping out oxygen in the internal space by applying a predetermined voltage between a first electrode and a second electrode; and a measuring cell including third and fourth electrodes and measuring a current flowing when a voltage is applied between the third electrode and the fourth electrode; wherein the first electrode is formed of porous cermet consisted of a noble metal and an oxygen ion conductive solid electrolyte, and the porosity of the first electrode is greater than or equal to 10% and less than or equal to 50%.

Abstract: A gas sensor for measuring NOx concentration in measurement gas based on sensor output depending on an amount of detected oxygen includes an oxygen concentration control part for controlling oxygen concentration in the measurement gas. The oxygen concentration control part allows a control of oxygen concentration in the measurement gas to set at a designated value even after being mounted on an automobile, so that dependency of the sensor output with respect to oxygen concentration can be quantitatively detected. The sensor output for detecting NOx concentration is corrected by estimating an amount of a change accompanying the sensitivity degradation of the sensor output with respect to NOx concentration on the basis of a difference between oxygen output characteristics of the sensor output of an actually-used sensor and oxygen output characteristics of a sensor in the initial state, and correcting the sensor output in accordance with the amount of the change.

Abstract: A sensor for specifying a concentration of a predetermined gas component in a measurement gas on the basis of a current flowing in an electrolyte by decomposition of the predetermined gas component, includes an internal space; a reference gas space; a pumping cell capable of pumping out oxygen in the internal space by applying a predetermined voltage between a first electrode and a second electrode; and a measuring cell including third and fourth electrodes and measuring a current flowing when a voltage is applied between the third electrode and the fourth electrode; wherein the first electrode is formed of porous cermet consisted of a noble metal and an oxygen ion conductive solid electrolyte, and the porosity of the first electrode is greater than or equal to 10% and less than or equal to 50%.

Abstract: A gas sensor for specifying a concentration of a predetermined gas component in a measurement gas on the basis of a current flowing in an electrolyte by decomposition of the predetermined gas component, includes an internal space; a reference gas space; a pumping cell capable of pumping out oxygen in the internal space by applying a predetermined voltage between a first electrode and a second electrode; and a measuring cell including a third electrode and a fourth electrode and measuring a current flowing between the third electrode and the fourth electrode when a voltage is applied between the third electrode and the fourth electrode; wherein the first electrode is formed of porous cermet consisted of noble metal containing gold of greater than or equal to 0.01 wt % and less than or equal to 0.95 wt %.

Abstract: A gas sensor element is heated at a temperature of 500° C. or higher for 15 minutes or more in a treatment atmosphere containing one or more gases selected from the gas group consisting of nitrogen (N2), oxygen (O2), carbon monoxide (CO), hydrogen (H2) and hydrocarbons (HC) and giving an air ratio of 0.80 to 1.10. In a gas sensor element to which such a treatment has been applied, a stable output is obtained without causing overshoot to an actual NOx concentration (input) even when a rapid exhaust gas change takes place.

Abstract: A gas sensor and nitrogen oxide sensor, which, when fitted to the exhaust system of an internal combustion engine, can suppress the influence of harmful substances contained in a measurement gas and can prevent the reduction in sensitivity over time. A harmful substance-trapping layer is formed at a gas inlet for introducing a to-be-measured gas from an external space into an internal space, and in a buffering space formed between diffusion resistance portions. In a trap-formed portion of a gas passage in which the harmful substance-trapping layer is formed, the measurement gas can pass in an amount of 80% or more of when the harmful substance-trapping layer is not formed in the trap-formed portion. A diffusion resistance is attained in the diffusion resistance portions; a harmful substance is trapped in the harmful substance-trapping layer; and the measurement gas is allowed to flow into a detection electrode side.