Gas sensor

A gas sensor, comprising:

• a solid electrolyte layer;
• a common oxygen reference electrode formed on a first side of the solid electrolyte layer and embedded within said sensor;
• two oxygen concentration electrodes formed side by side on a second side of the solid electrolyte layer such that both oxygen concentration electrodes are opposed to the common reference electrode;
• a common cavity formed over the two oxygen concentration electrodes, said two oxygen concentration electrodes being exposed to the common cavity so as to be in contact with the same gas atmosphere;
• means for measuring the concentration of NO, comprising means for detecting a voltage across the two oxygen concentration electrodes;
• and
• means for establishing an atmosphere of constant oxygen concentration in the vicinity of the embedded common oxygen reference electrode;
• wherein one of the oxygen concentration electrodes is an active electrode containing Pt, and the other oxygen concentration electrode is an inactive electrode containing Pt and Au,
• said gas sensor further comprising means for measuring electric potential between the inactive electrode and the common oxygen reference electrode, and
• said sensor outputting a voltage across the two oxygen concentration electrodes which varies substantially linearly with NO concentration.