DIN EN ISO 6145-9:2011-03

This document (EN ISO 6145-9:2010) contains the German translation of the International Standard ISO 6145-9, which has been prepared by Technical Committee ISO/TC 158 "Analysis of gases" (secretariat: NEN, Netherlands). The responsible national Committee is Working Committee NA 062-05-73 AA "Gasanalyse und Gasbeschaffenheit" ("Gas analysis and gas quality") of the Materials Testing Standards Committee (NMP).
This part of ISO 6145 is one of a series of International Standards dealing with various dynamic volumetric methods used for the preparation of calibration gas mixtures. This part specifies a method for continuous production of calibration gas mixtures containing one or more readily condensable components. A relative expanded uncertainty of measurement, U, obtained by multiplying the relative combined standard uncertainty by a coverage factor k = 2, of not greater than 1 %, can be obtained using this method.
Unlike the methods presented in the other parts of ISO 6145, the method described in this part does not require accurate measurement of flow rates since flow rates do not appear in the equations for calculation of the volume fraction.
Readily condensable gases and vapours commonly become adsorbed on surfaces, and it is therefore difficult to prepare stable calibration gas mixtures of accurately known composition, containing one or several of such components, by means of static methods. In addition, these calibration gas mixtures cannot be maintained under a pressure near the saturation limit without the occurrence of condensation. The saturation method can be employed to prepare mixtures of this type.