Patent ID: 7228725

Claim:
A gas sensor for sensing a gas stream constituent, the gas sensor comprising: (a) a thermally conductive, electrically insulative substrate; (b) a first gas-sensing element mounted on said substrate, said first gas-sensing element capable of sensing said constituent in a first concentration range; (c) a reference element mounted on said substrate, said reference element and said first gas-sensing element having congruent electrical properties, said reference element insensitive to said constituent; (d) a heating element mounted on said substrate and substantially circumscribing said first gas-sensing element and said reference (e) a temperature-sensing element mounted on said substrate and substantially circumscribing said first gas-sensing element and said reference element; (f) a second gas-sensing element mounted on said substrate capable of sensing said constituent in a second concentration range such that said heating element imparts at least some convective heat to said second gas-sensing element; wherein said temperature-sensing element substantially circumscribes said heating element.