Amperometric gas sensor containing a solid electrolyte

Claim 1

Apparatus for sensing selected gas constituents of an ambient gas comprising: a sensing electrode having a surface positioned and arranged to be exposed to said ambient gas, a reference electrode spaced apart from said sensing electrode, a counter electrode spaced apart from said sensing electrode and said reference electrode, an alkali salt in the solid state in physical and electrical contact with said sensing electrode, said reference electrode and said counter electrode, circuit means including means for providing a current from said counter electrode through said alkali salt to said sensing electrode to maintain a predetermined voltage on said sensing electrode with respect to said reference electrode. means for heating said alkali salt to at least a predetermined temperature at which said alkali salt conducts electricity, and means responsive to electric current from said sensing electrode to provide an indication of the concentration of a gas constituent in said ambient gas.