This part of ISO 6145 is one of a series of International Standards dealing with dynamic volumetric methods
used for the preparation of calibration gas mixtures. This part specifies a method for continuous production of
calibration gas mixtures, containing two or more components, from pure gases or other gas mixtures by use of
commercially available thermal mass-flow controllers.
If this method is employed for the preparation of calibration gas mixtures, the optimum performance is as
follows: the relative expanded uncertainty of measurement, U, obtained by multiplying the combined standard
uncertainty by a coverage factor k = 2, is not greater than 2 %.
If pre-mixed gases are used instead of pure gases, mole fractions below 10 can be obtained. The
measurement of mass flow is not absolute and the flow controller requires independent calibration.
The merits of the method are that a large quantity of the gas mixture can be prepared on a continuous basis
and that multicomponent mixtures can be prepared as readily as binary mixtures if the appropriate number of
thermal mass-flow controllers is utilized.
NOTE Gas-blending systems based upon thermal mass-flow controllers, some including the facility of
computerization and automatic control, are commercially available.
BS EN ISO 6145-7:2010 Referenced Document
ISO 6143 Gas analysis - Comparison methods for determining and checking the composition of calibration gas mixtures
ISO 6145-1:2003 Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 1: Methods of calibration
ISO 7504 Gas analysis - Vocabulary*， 2015-05-01 Update
BS EN ISO 6145-7:2010 history
2019BS EN ISO 6145-7:2018 Gas analysis. Preparation of calibration gas mixtures using dynamic methods. Thermal mass-flow controllers
2009BS EN ISO 6145-7:2010 Gas analysis. Preparation of calibration gas mixtures using dynamic volumetric methods. Thermal mass-flow controllers