Gas sensor and sensor element

A gas sensor comprising a sensor element and a control device, and configured to measure a concentration of a specific gas in a measurement gas,

• wherein:
• the sensor element includes:
• an element body having an oxygen-ion-conductive solid electrolyte layer and having, inside the element body, a first chamber, a second chamber, and a third chamber that are not in communication with each other and that are each reachable by the measurement gas from outside the sensor element;
• a first pump cell constituted including a first inner electrode disposed in the first chamber and a first outer electrode disposed on an outer surface of the element body;
• a second pump cell constituted including a second inner electrode disposed in the second chamber and a second outer electrode disposed on an outer surface of the element body;
• and
• a third pump cell constituted including a third inner electrode disposed in the third chamber and a third outer electrode disposed on an outer surface of the element body;
• the control device performs:
• a first pump cell control processing in which oxygen is pumped out from around the first inner electrode to around the first outer electrode by controlling the first pump cell, thereby reducing reduction target gases that are oxide gases of two or more kinds in the measurement gas in the first chamber;
• a second pump cell control processing in which, by controlling the second pump cell, oxygen is pumped out from around the second inner electrode to around the second outer electrode, while suppressing, as compared with the first pump cell control processing, the reduction of a first gas species in the measurement gas in the second chamber, the first gas species being one or more kinds of oxide gas included among the reduction target gases, but not all kinds thereof;
• and
• a third pump cell control processing in which, by controlling the third pump cell, oxygen is pumped out from around the third inner electrode to around the third outer electrode, while suppressing, as compared with the second pump cell control processing, the reduction of a second gas species in the measurement gas in the third chamber, the second gas species being one or more kinds of oxide gas other than the first gas species, included among the reduction target gases;
• and
• the control device measures, as the concentration of the specific gas, at least two of the first to fourth concentrations by performing at least two types of the following concentration measurement processing, the at least two types being selected in a combination that uses all of the first to third pump currents:
• a first concentration measurement processing in which a first concentration, which is a concentration of the first gas species in the measurement gas, is measured based on a first pump current that flows through the first pump cell by the first pump cell control processing and a second pump current that flows through the second pump cell by the second pump cell control processing;
• a second concentration measurement processing in which a second concentration, which is a concentration of the second gas species in the measurement gas, is measured based on the second pump current and a third pump current that flows through the third pump cell by the third pump cell control processing;
• a third concentration measurement processing in which a third concentration, which is a total concentration of the reduction target gases other than the first gas species and the second gas species and oxygen in the measurement gas, is measured based on the third pump current;
• and
• a fourth concentration measurement processing in which a fourth concentration, which is a total concentration of the first gas species and the second gas species in the measurement gas, is measured based on the first pump current and the third pump current.