Gas sensor

A method in a gas sensor including:

• an element body including an oxygen-ion-conductive solid electrolyte layer, a measurement-object gas flow section being provided within the element body to allow a measurement-object gas to be introduced into the measurement-object gas flow section and flow through the measurement-object gas flow section;
• a preliminary pump cell that pumps oxygen into a preliminary chamber, the preliminary chamber being provided in the measurement-object gas flow section downstream of a first diffusion-rate-limiting portion;
• a main pump cell that adjusts an oxygen concentration of a first internal space, the first internal space being provided in the measurement-object gas flow section downstream of the preliminary chamber and being separated from the preliminary chamber by a second diffusion-rate-limiting portion;
• an auxiliary pump cell that adjusts an oxygen concentration of a second internal space, the second internal space being provided in the measurement-object gas flow section downstream of the first internal space and being separated from the first internal space by a third diffusion-rate-limiting portion;
• a measurement electrode disposed on an inner peripheral surface of a measurement chamber, the measurement chamber being provided downstream of the second internal space and being separated from the second internal space by a fourth diffusion-rate-limiting portion;
• a reference electrode that is disposed within the element body and to which a reference gas is to be introduced, the reference gas serving as a reference for detecting a specific gas concentration of a specific gas in the measurement-object gas;
• and
• a measurement voltage detection sensor cell that detects a measurement voltage present between the reference electrode and the measurement electrode,
• the method comprising the steps of:
• controlling the preliminary pump cell to prevent the measurement-object gas from reaching the first internal space in a state in which the measurement-object gas is a low-oxygen atmosphere;
• controlling the main pump cell to adjust the oxygen concentration in the measurement object gas in the first internal space;
• controlling the auxiliary pump cell to adjust the oxygen concentration in the measurement object gas in the second internal space;
• and
• obtaining, based on the measurement voltage, a detection value according to oxygen produced in the measurement chamber and, based on the detection value,
• detecting the specific gas concentration in the measurement-object gas, the oxygen being oxygen derived from the specific gas,
• wherein the gas sensor further includes a measurement-object gas-side electrode disposed at a portion that is to be exposed to the measurement-object gas that is outside of the element body, and
• wherein the preliminary pump cell pumps oxygen into the preliminary chamber from a vicinity of the measurement-object gas-side electrode.