Development of a Novel Low-Cost, Low-Power, Narrow-Band Oxygen Sensor for Small Engine Applications. (1 of 3)

Global concerns over pollution have led to increasingly strict emissions legislation targeting small engines, which currently pollute at a much greater level than modern multi-cylinder automotive engines. Closed-loop control may be required to meet many future legislation requirements; however, such systems can be impractical due to high added component costs. A necessary component for closed-loop engine control is an oxygen sensor. Existing automotive oxygen sensors are too large, require too much power, and are far too expensive to be suitable for the vast majority of the global small engine applications; therefore, some manufacturers have developed smaller and/or unheated versions based on their existing sensors to meet this emerging need. The ability to miniaturize resistive based sensors well below that of traditional Nernst (zirconia based) oxygen sensors affords the opportunity to meet future emissions standards with less of an impact on cost.

In this study, a sub-miniature resistance-based narrow-band oxygen sensor was developed and its response to various exhaust lambda values was characterized at various temperatures. A circuit is proposed and tested to produce a signal compatible with a zirconia narrow-band oxygen sensor, thus minimizing the applications engineering efforts required to implement such a sensor. Results indicate this sensor platform is less expensive and affords many performance advantages superior to existing zirconia-based narrow-band sensors and is well suited for many applications that would otherwise not have a cost-effective sensor for closed-loop control to meet emerging emissions standards.