P2.7 - Pulsed Polarization of Lambda Probes – Evaluation of the Polarization Current
- AMA Conferences 2013
2013-05-14 - 2013-05-16
- Proceedings SENSOR 2013
- P2 - Gas Sensors
- S. Fischer, R. Moos - University of Bayreuth (Germany), R. Pohle, E. Magori, M. Fleischer - Siemens AG, Munich (Germany), B. Farber - BJR Sensors, LLC, Solon (USA)
- 732 - 735
Conventional thimble type lambda sensors show strong response on NOx by evaluation of the open circuit discharge characteristics after defined polarizations with alternating signs. The sensor signal is dependent on oxygen or water concentration but the influence on discharge characteristics is consistent with Nernstian behavior. This confirms the feasibility of a pulsed mode operated lambda probe as a NOx sensor for exhaust gas measurements. To find the underlying mechanism of this polarization technique, the current during the voltage pulse is evaluated in a simulated combustion exhaust gas with varying oxygen and moisture levels. By increasing the oxygen or water content in the exhaust the polarization current decreases at both polarization directions. Platinum oxidation during voltage pulses is assumed to be responsible for this effect.