Gas sensing apparatus

A gas sensor for sensing the components contained in an exhaust gas from an internal combustion engine and for determining an equivalence ratio of an air-fuel mixture supplied to the engine having:

• a pipe-shaped casing,
• a tubular, electrically insulating ceramic body provided in said pipe-shaped casing,
• first and second sinter elements fixed to one end of said ceramic body and being spaced apart from each other, said first sinter element being made of titania carrying at least on a surface thereof a catalyst for promoting oxidating reaction of the gas components, an electric resistance value of said first sinter element being varied depending on the gas components and exhaust gas temperature, and said second sinter element being made of substantially only titania, an electric resistance value of said second sinter element being varied depending primarily on the exhaust gas temperature,
• a plurality of electrodes connected to said first and second sinter elements for taking out electrically the changes in the electric resistance values of said first and second sinter elements, and
• a single fixed resistor permanently connected in parallel electric circuit relation with said second sinter element, the resistance value of said single fixed resistor being significantly smaller than the resistance value of said second sinter element at a low temperature of said gas thereby rendering a voltage developed across said second sinter element primarily governed by the resistance value of said single fixed resistor, and with the resistance value of said second sinter element being significantly smaller than the resistance value of said single fixed resistor in a temperature range above said low temperature of said gas thereby rendering the voltage developed across said second sinter element as primarily governed by the resistance value of said second sinter element.