Abstract
Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well.
Highlights
In order to monitor the air-to-fuel ratio and to detect directly the aging status of exhaust gas aftertreatment systems, ceramic oxygen gas sensors have been serialized [1,2]
It should show the same temperature dependency as the non-activated one. It acts as a resistive -sensor and is not sensitive to HC anymore. The ratio of both sensor signals is expected to result in a sensor signal that is almost unaffected by temperature and oxygen content of the exhaust
It was verified that it is possible to establish a constant oxygen concentration at the cavity where the sensor film is located by applying an appropriate pumping voltage to the cell [15]
Summary
In order to monitor the air-to-fuel ratio and to detect directly the aging status of exhaust gas aftertreatment systems, ceramic oxygen gas sensors have been serialized [1,2]. It was verified that it is possible to establish a constant oxygen concentration at the cavity where the sensor film is located by applying an appropriate pumping voltage to the cell [15]. It is possible to establish a defined oxygen concentration within the requested range at the position of the sensor film independently of the oxygen partial pressure in the exhaust gas. The catalytic activation of one of the sensor layers is discussed and sensors with Ga2O3 and 1% Nb-doped SrTiO3 as gas sensitive films have been tested. These are the pilot test of the new sensor platform. The main function of the platform, which is the detection of HCs under a defined oxygen atmosphere independent of the oxygen partial pressure in the exhaust gas, has to be investigated in the step
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