Automotive exhaust gas sensing systems

Gas sensors have become an integral component of control systems for internal combustion engines to provide information for feedback control of air-to-fuel ratio (A/F) to achieve improved vehicle performance and fuel economy as well as decreased levels of emission. Increasingly stringent limits on evaporative emissions as well as the requirement of having on-board diagnostics (OBD), which includes catalyst monitoring, necessitate the monitoring of exhaust gas constituents [i.e., carbon monoxide (CO), hydrocarbons (HCs), and oxides of nitrogen (NO_x)]. The different sensing requirements, testing procedures, environmental parameters, and need for microsystem-based realizations are discussed