1 Scope
This document describes the static gravimetric preparation of Class II calibration
gas mixtures and describes a method for calculating the measurement uncertainty associated
with the amount fraction of each component. In addition to all of the contributions
to the measurement uncertainty mentioned in ISO 6142‑1, this document also considers the uncertainty resulting from the validation process
for Class II mixtures that are not individually verified, as is the case for Class
I mixtures.
This document extends the uncertainty evaluation described in ISO 6142‑1 to include the effects of batch production and the verification process. It provides
guidance on how to derive an uncertainty budget that is representative of a particular
category of mixtures .
Methods for the batch production of more than one mixture in a single process are
included in this document.
This document is only applicable to mixtures of gaseous or totally vaporized components,
which can be introduced into the cylinder in the gaseous or liquid state. Both binary
and multi-component gas mixtures are covered by this document.
This document is limited to non-reactive molecules/components that are greater than
or equal to an amount fraction of 100 μmol/mol. This document excludes components
that react with each other, or with common mixture contaminants such as water vapour
or oxygen or react with the inner surface of the cylinder and valve in the form of
absorption or adsorption.
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