EXHAUST GAS SENSOR

摘要

A differential calorimetric gas sensor (10) which includes a sensing element (12) having a catalytic layer (14) disposed on a multi-layered substrate (26). Catalytic layer (14) includes an active catalyst region (14a) which oxidizes total combustibles within an exhaust gas stream and a reference catalyst region (14b) which oxidizes selective combustibles within the exhaust gas stream. An electrochemical oxygen source (18) is disposed on an opposite side of multi-layer substrate (26) from sensing element (12). An oxygen sensor cell (170) may be incorporated into electromechanical oxygen source (18). The multi-layered substrate (26) includes a plurality of overlaying insulating layers in which an intermediate layer (60) and a bottom layer (64) support primary heaters (58, 62), and in which another intermediate layer (52) supports compensation heaters (50a, 50b). The primary heaters (58, 62) function to maintain sensor (10) at a substantially constant temperature, while the compensation heaters (50a, 50b) function to restore temperature deviations determined by temperature-sensitive elements (46a, 46b) located on an inner layer (48) overlaying the compensation heaters (50a, 50b) resulting from the catalytic reactions taking place at the surfaces (34a, 34b) of the catalyst regions (14a, 14b). The control circuitry (300) operates to control the primary heater (58, 62) and the compensation heaters (50a, 50b), as well as to minimize the response variations of the temperature-sensitive elements (46a, 46b).