Study of Interferences for ULEV-CVS Measurement, Related to the Complete Measuring System, Discussion of Error Sources, Cross-Sensitivity and Adsorption

E. Schiefer; W. Schindler; H. Schimpl

doi:10.4271/2000-01-0796

2000-03-06

Study of Interferences for ULEV-CVS Measurement, Related to the Complete Measuring System, Discussion of Error Sources, Cross-Sensitivity and Adsorption 2000-01-0796

Bag emission measurements on Ultra Low Emission Vehicles require measurement sensitivities in the 1 ppm range for HC and NO_x and measurement resolutions well below this to obtain sufficient accuracy and repeatability. Additionally, an analysis of the C₂ to C₁₂ components is required. In these emission ranges, adsorption, desorption, diffusion and chemical reaction processes may produce significant effects to the measuring values.

Therefore, improvements are necessary to avoid this as far as possible. However, for physical reasons these effects cannot be eliminated completely.

For example:

Particle filters are not 100% efficient and particles will slowly contaminate the surfaces.
Due to physical and chemical processes with some gas components, even stainless steel and Teflon can change their characteristics.

Problems resulting from the physical and chemical effects and provisions to minimize the influences to the measuring accuracy and system stability are discussed. This includes contamination check procedures and possibilities for measuring and correcting offset or drift effects caused by these phenomena.

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Study of Interferences for ULEV-CVS Measurement, Related to the Complete Measuring System, Discussion of Error Sources, Cross-Sensitivity and Adsorption 2000-01-0796

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