Gas sensor

A gas sensor that detects a specific gas concentration which is a concentration of a specific gas in a measurement-object gas, the gas sensor comprising:

• an element body which includes an oxygen-ion-conductive solid electrolyte layer, and is internally provided with a measurement-object gas flow portion that introduces the measurement-object gas and causes the measurement-object gas to flow;
• a first pump cell including a first inner electrode disposed in the measurement-object gas flow portion, the first pump cell being configured to perform pumping of oxygen;
• a second pump cell including a second inner electrode disposed in the measurement-object gas flow portion, the second pump cell being configured to perform pumping of oxygen;
• a heater configured to heat the element body;
• a first impedance measurer configured to measure a first impedance by applying a voltage to the first inner electrode;
• a second impedance measurer configured to measure a second impedance by applying a voltage to the second inner electrode;
• a control apparatus configured to perform a heater control process of controlling the heater so that the first impedance reaches a target value, and a correction process of correcting, based on the second impedance, a second pump current which flows through the second pump cell or a value derived based on the second pump current;
• a reference electrode disposed inside the element body to come into contact with a reference gas which serves as a reference for detecting the specific gas concentration;
• and
• an adjustment pump cell including the first pump cell, the adjustment pump cell being configured to adjust an oxygen concentration in an oxygen concentration adjustment chamber of the measurement-object gas flow portion,
• wherein the first inner electrode is disposed in the oxygen concentration adjustment chamber,
• the second inner electrode is an inner measurement electrode disposed in a measurement chamber provided downstream of the oxygen concentration adjustment chamber of the measurement-object gas flow portion,
• the second pump cell is a measurement pump cell that pumps out oxygen originating from the specific gas from the measurement chamber,
• the control apparatus performs an adjustment pump control process of controlling the adjustment pump cell so that the oxygen concentration in the oxygen concentration adjustment chamber reaches a target concentration, an oxygen concentration detection process of detecting an oxygen concentration in the measurement-object gas based on a first pump current which is caused to flow through the first pump cell by the adjustment pump control process, a measurement pump control process of feedback controlling a control voltage to be applied to the measurement pump cell so that a voltage across the reference electrode and the inner measurement electrode reaches a target value, and a specific gas concentration detection process of detecting the specific gas concentration in the measurement-object gas based on a measurement pump current that is the second pump current caused to flow through the measurement pump cell by the measurement pump control process, and
• in the correction process, the control apparatus corrects, based on the second impedance, the measurement pump current in the specific gas concentration detection process or the specific gas concentration.