Gas sensor and method of identifying deviation of reference potential of the same

A gas sensor comprising a sensor element and a control device, and being configured to detect a specific gas concentration which is a concentration of a specific gas in a measurement-object gas,

• the sensor element including:
• an element body including an oxygen-ion-conductive solid electrolyte layer and provided with a measurement-object gas flow portion therein, the measurement-object gas flow portion being configured to introduce the measurement-object gas and cause the measurement-object gas to flow therethrough;
• a measurement electrode disposed in a measurement chamber of the measurement-object gas flow portion;
• and
• a reference electrode disposed inside the element body to come into contact with a reference gas that serves as a reference for detection of the specific gas concentration,
• wherein the control device is configured to measure a voltage across a ground and the reference electrode, and identify a deviation of a reference potential that is an electrical potential of the reference electrode by performing one or more of magnitude relationship comparison of the measurement value with a normal value, calculation of a difference or a ratio between the measurement value and the normal value, comparison of the measurement value with a predetermined acceptable range, and determination as to whether a measurement value is in the predetermined acceptable range.