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 onboard diagnostics (OBD), which includes catalyst monitoring, necessitate the monitoring of exhaust gas constituents [i.e., carbon monoxide (CO), hydrocarbons (HCs), and oxides of nitrogen (NOx)]. The different sensing requirements, testing procedures, environmental parameters, and need for microsystem-based realizations are discussed