NF EN ISO 6145-7
Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 7 : thermal mass-flow controllers
ISO 6145-7:2009 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 10-6 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.
ISO 6145-7:2009 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 10-6 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.
<p>ISO 6145-7:2009 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. </p> <p>If this method is employed for the preparation of calibration gas mixtures, the optimum performance is as follows: the relative expanded uncertainty of measurement, <i>U</i>, obtained by multiplying the combined standard uncertainty by a coverage factor <i>k</i> = 2, is not greater than 2 %.</p> <p>If pre-mixed gases are used instead of pure gases, mole fractions below 10<sup>-</sup><sup>6</sup> can be obtained. The measurement of mass flow is not absolute and the flow controller requires independent calibration.</p> <p>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.</p>
<p>ISO 6145 is a series of documents dealing with various dynamic methods used for the preparation of calibration gas mixtures. This document specifies a method for continuous preparation of calibration gas mixtures, from nominally pure gases or gas mixtures by use of thermal mass-flow controllers. The method is applicable to preparation of mixtures of non-reacting species, i.e. those which do not react with any material of construction of the flow path in the thermal mass-flow controller or the ancillary equipment.</p> <p>If this method is employed for preparation of calibration gas mixtures the optimum performance is as follows: the relative expanded measurement uncertainty <i>U</i>, obtained by multiplying the standard uncertainty by a coverage factor <i>k</i> = 2, is not greater than 2 %.</p> <p>If pre-mixed gases are used instead of pure gases, mole fractions below 10<sup>−6</sup> can be obtained. The measurement of mass flow is not absolute and the flow controller requires independent calibration.</p> <p>The merits of the method are that a large quantity of the calibration gas mixture can be prepared on a continuous basis and that multi-component mixtures can be prepared as readily as binary mixtures if the appropriate number of thermal mass-flow controllers is utilized.</p> <p>NOTE Gas blending systems, based upon thermal mass-flow controllers, and some including the facility of computerization and automatic control, are commercially available.</p>
- Avant-proposiv
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1 Domaine d'application1
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2 Références normatives1
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3 Termes et définitions2
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4 Principe2
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5 Configuration2
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5.1 Généralités2
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5.2 Régulateur thermique de débit massique utilisant un générateur de courant constant2
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5.3 Régulateur thermique de débit massique opérant à température constante3
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6 Préparation de mélanges de gaz4
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6.1 Description du mode opératoire expérimental4
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6.2 Zone de validité6
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6.3 Conditions de fonctionnement7
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7 Calculs7
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7.1 Fraction volumique7
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7.2 Sources d'incertitude7
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7.3 Incertitude de mesure8
- Annexe A (informative) Prémélanges gazeux utilisés pour la préparation de mélanges fortement dilués9
- Annexe B (informative) Conseils pratiques10
- Annexe C (informative) Calcul des incertitudes12
- Bibliographie15
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