Gas sensor

A gas sensor of a mixed-potential type including a sensor element formed of a solid electrolyte having oxygen-ion conductivity and configured to measure a concentration of a predetermined gas component in measurement gas, wherein

• said sensor element includes:
• an internal space that is communicated with an external space through a gas introduction part provided on one leading end part side and to which said measurement gas is introduced from said external space;
• a sensing electrode provided at a part of said sensor element where said sensing electrode is contactable with the measurement gas;
• a reference gas introduction space to which reference gas is introduced;
• a reference electrode provided in said reference gas introduction space;
• a sensing cell including said sensing electrode and said reference electrode;
• an oxygen pump cell including an inner side pump electrode formed facing to said internal space, an outer side pump electrode formed on an outer surface of said sensor element, and said solid electrolyte between said inner side pump electrode and said outer side pump electrode, and configured to pump out oxygen in said internal space when a predetermined oxygen pump voltage is applied between said inner side pump electrode and said outer side pump electrode;
• and
• a heater capable of heating at least said sensing cell and said oxygen pump cell,
• said gas sensor further includes:
• an oxygen pump power source configured to apply said predetermined oxygen pump voltage between said inner side pump electrode and said outer side pump electrode;
• concentration specification element configured to specify the concentration of said predetermined gas component in said measurement gas, and
• while said measurement gas is in contact with said sensing electrode and introduced in said internal space, said heater heats said sensing cell to a first heating temperature of 400° C. or higher and 600° C. or lower and heats said oxygen pump cell to a second heating temperature of 580° C. or higher and 850° C. or lower in a temperature range determined in accordance with a diffusion resistance provided to said measurement gas by said gas introduction part, and said oxygen pump cell pumps out oxygen in said measurement gas in said internal space, said concentration specification element specifies the concentration of a measurement target gas component in said measurement gas based on:
• a sensor output value as a potential difference occurring between said sensing electrode and said reference electrode in accordance with the concentration of said predetermined gas component in said measurement gas;
• and
• the concentration of oxygen in said measurement gas specified based on a magnitude of a pump current flowing between said inner side pump electrode and said outer side pump electrode when oxygen in said measurement gas in said internal space is pumped out by said oxygen pump cell.