Detection of NOx in Combustion Engine Exhaust Gas by Applying the Pulsed Polarization Technique on YSZ Based Sensors

Abstract

The pulsed polarization measurement technique applied on sensor devices based on yttria stabilized zirconia (YSZ) with porous platinum electrodes enables the detection of low ppm concentrations of NOx in exhaust gas applications with a simple device. Pulsed polarization is based on alternating voltage pulses with intermediate pauses for self discharging. The discharge characteristics after polarization depends strongly on NOx content in the low ppm range. Due to faster discharging in NOx containing atmospheres compared to base gas, the voltage difference between the discharge curves can act as a concentration dependent parameter. Sensor probes for usage in exhaust gas conditions have been built. The feasibility of NOx sensing in diesel exhaust gas by use of a planar cost-effective YSZ sensor element is evaluated in detail in comparison to commercial NOx exhaust sensors and referenced with gas analysis equipment.

Keywords

• exhaust gas sensor
• yttria stabilized zirconia
• pulsed polarization