A gas sensor is equipped with a housing, an insulator retained by an inner periphery of the housing, a sensing device having a front end portion protruding from a front end surface of the insulator, and a protective cover which covers a front end portion of the sensing device. A pump electrode and a sensor electrode are disposed in a front end portion of the solid electrolyte body. The pump electrode is exposed to a measurement gas and regulates the concentration of oxygen in the measurement gas. The sensor electrode is exposed to the measurement gas and measures the concentration of a given gas component in the measurement gas after being regulated in concentration of oxygen by the pump electrode. A base end portion of the sensor electrode in a lengthwise direction is located closer to a base end side of the gas sensor than a front end surface of the housing is. This minimizes a variation in temperature of the sensor electrode and enhances the accuracy in measuring the concentration of the given gas component.

A gas sensor is equipped with a housing, an insulator retained by an inner periphery of the housing, a sensing device having a front end portion protruding from a front end surface of the insulator, and a protective cover which covers a front end portion of the sensing device. A pump electrode and a sensor electrode are disposed in a front end portion of the solid electrolyte body. The pump electrode is exposed to a measurement gas and regulates the concentration of oxygen in the measurement gas. The sensor electrode is exposed to the measurement gas and measures the concentration of a given gas component in the measurement gas after being regulated in concentration of oxygen by the pump electrode. A base end portion of the sensor electrode in a lengthwise direction is located closer to a base end side of the gas sensor than a front end surface of the housing is. This minimizes a variation in temperature of the sensor electrode and enhances the accuracy in measuring the concentration of the given gas component.

Provided are: an electrode for a gas sensor formed as a porous electrode so as to stably allow reduction in electrode resistance for excellent low-temperature activity; and a gas sensor. The electrode (108, 110) for the gas sensor is adapted for use on a surface of a solid electrolyte body (109), which is predominantly formed of zirconia, and contains particles (2) of a noble metal or an alloy thereof, first ceramic particles (4) of stabilized zirconia or partially stabilized zirconia and second ceramic particles (6) of one or more selected from the group consisting of Al.sub.2O.sub.3, MgO, La.sub.2O.sub.3, spinel, zircon, mullite and cordierite, wherein the second ceramic particles are contained in an amount smaller than that of the first ceramic particles.

Provided are: an electrode for a gas sensor formed as a porous electrode so as to stably allow reduction in electrode resistance for excellent low-temperature activity; and a gas sensor. The electrode (108, 110) for the gas sensor is adapted for use on a surface of a solid electrolyte body (109), which is predominantly formed of zirconia, and contains particles (2) of a noble metal or an alloy thereof, first ceramic particles (4) of stabilized zirconia or partially stabilized zirconia and second ceramic particles (6) of one or more selected from the group consisting of Al.sub.2O.sub.3, MgO, La.sub.2O.sub.3, spinel, zircon, mullite and cordierite, wherein the second ceramic particles are contained in an amount smaller than that of the first ceramic particles.

A gas sensor includes a main pump cell, a storage unit that stores information about a zero point in a first correspondence relationship, where the first correspondence relationship is a linear correspondence relationship between the oxygen concentration in a measurement-object gas and the main pump current, an oxygen-concentration-detecting unit that detects the oxygen concentration in a measurement-object gas, based on a measured value p of the main pump current and the information about the zero point, and a measured-value-obtaining unit that performs a second control process and that obtains a measured value b1 at a measurement point B1 at which a known value of the oxygen concentration and the main pump current are relevant to each other with a measurement timing. The oxygen-concentration-detecting unit makes zero point correction such that a divergence of the zero point from the first correspondence relationship is corrected based on the measured value b1.

A gas sensor includes a main pump cell, a storage unit that stores information about a zero point in a first correspondence relationship, where the first correspondence relationship is a linear correspondence relationship between the oxygen concentration in a measurement-object gas and the main pump current, an oxygen-concentration-detecting unit that detects the oxygen concentration in a measurement-object gas, based on a measured value p of the main pump current and the information about the zero point, and a measured-value-obtaining unit that performs a second control process and that obtains a measured value b1 at a measurement point B1 at which a known value of the oxygen concentration and the main pump current are relevant to each other with a measurement timing. The oxygen-concentration-detecting unit makes zero point correction such that a divergence of the zero point from the first correspondence relationship is corrected based on the measured value b1.

A method and a device are described for detecting at least a portion of a measuring gas component containing bound oxygen in a gas mixture, in particular in an exhaust gas of an internal combustion engine, in a measuring gas chamber by detecting a portion of oxygen that is generated by a reduction of the measuring gas component containing the bound oxygen, in the presence of molecular oxygen, in the device, which includes at least one first pump cell, one reference cell, and one second pump cell. The method includes the following steps: a) generating a first pump current in the first pump cell in such a way that transport of a first portion of oxygen ions takes place between the measuring gas chamber and the surroundings of the device; b) applying a reference pump current to the reference cell in such a way that a second portion of the oxygen ions is transported into a reference gas chamber; c) decomposing the measuring gas component containing the bound oxygen by catalysis at an electrode of the second pump cell, as the result of which additional molecular oxygen is generated from the measuring gas component; d) applying a second pump current to the second pump cell in such a way that a portion of further oxygen ions that are formed from the additional molecular oxygen is transported into the reference gas chamber; and e) holding a sum of currents, formed from the reference pump current and from the second pump current, constant.

A method and a device are described for detecting at least a portion of a measuring gas component containing bound oxygen in a gas mixture, in particular in an exhaust gas of an internal combustion engine, in a measuring gas chamber by detecting a portion of oxygen that is generated by a reduction of the measuring gas component containing the bound oxygen, in the presence of molecular oxygen, in the device, which includes at least one first pump cell, one reference cell, and one second pump cell. The method includes the following steps: a) generating a first pump current in the first pump cell in such a way that transport of a first portion of oxygen ions takes place between the measuring gas chamber and the surroundings of the device; b) applying a reference pump current to the reference cell in such a way that a second portion of the oxygen ions is transported into a reference gas chamber; c) decomposing the measuring gas component containing the bound oxygen by catalysis at an electrode of the second pump cell, as the result of which additional molecular oxygen is generated from the measuring gas component; d) applying a second pump current to the second pump cell in such a way that a portion of further oxygen ions that are formed from the additional molecular oxygen is transported into the reference gas chamber; and e) holding a sum of currents, formed from the reference pump current and from the second pump current, constant.

An inspection apparatus capable of performing responsivity inspection on a plurality of gas sensors at equivalent accuracies is provided. The inspection apparatus includes a plurality of inspected sensor disposing parts that are provided halfway through one gas flow path at equal intervals in an extending direction of the flow path and in each of which a gas sensor to be inspected is disposed, and a plurality of straightening plates provided upstream of each of the inspected sensor disposing parts on the gas flow path and separated at a constant distance from the inspected sensor disposing parts. The straightening plates each include a rectangular opening orthogonal to the gas flow path and open to the gas flow path. When the gas flow path extends in one direction in a horizontal plane, the opening has a longitudinal direction along a direction orthogonal to the one direction in the horizontal plane.

An inspection apparatus capable of performing responsivity inspection on a plurality of gas sensors at equivalent accuracies is provided. The inspection apparatus includes a plurality of inspected sensor disposing parts that are provided halfway through one gas flow path at equal intervals in an extending direction of the flow path and in each of which a gas sensor to be inspected is disposed, and a plurality of straightening plates provided upstream of each of the inspected sensor disposing parts on the gas flow path and separated at a constant distance from the inspected sensor disposing parts. The straightening plates each include a rectangular opening orthogonal to the gas flow path and open to the gas flow path. When the gas flow path extends in one direction in a horizontal plane, the opening has a longitudinal direction along a direction orthogonal to the one direction in the horizontal plane.