EUROMET.QM-K3: automotive emission gasmeasurements

Abstract

Following up the CCQM-K3 key comparison on automotive exhaust gas measurements, EUROMETorganized a regional key comparison, EUROMET.QM-K3. The objectives were essentially the same as for CCQM-K3: to compare the measurement capabilities of national metrological institutes (NMIs) in measuring amount-of-substance fractions of carbon monoxide, carbon dioxide and propane in nitrogen (``automotive gas mixture''). The comparison was carried out at an amount-of-substance fraction level of 32 mmol/mol carbon monoxide, 135 mmol/mol carbon dioxide, and 2.05 mmol/mol propane in nitrogen (balance gas). EUROMET.QM-K3 was organized by the Nederlands Meetinstituut-Van Swinden Laboratorium (NMi-VSL, the Netherlands). Each of the seven participants received its own gas mixture, prepared gravimetrically in accordance with ISO 6142. The preparation data were used to establish reference values for each of the components of each of the mixtures. To demonstrate the validity of the reference values thus assigned, the gas mixtures were compared with primary standard gas mixtures and previously prepared automotive gas mixtures. Where appropriate, the uncertainty of this verification experiment has been included in the uncertainty of the reference values. The target for agreement among the NMIs, set at 1 % relative for all components, was generally met. Most participants used gas chromatography as a measurement technique, with a thermal conductivity detector (TCD) for carbon monoxide and carbon dioxide, and a flame ionization detector (FID) for propane. One participant used a non-dispersive infrared monitor (NDIR) for carbon dioxide.