Abstract
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.
General information
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Status: WithdrawnPublication date: 2009-04Stage: Withdrawal of International Standard [95.99]
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Edition: 2Number of pages: 15
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Technical Committee :ISO/TC 158ICS :71.040.40
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Life cycle
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Previously
WithdrawnISO 6145-7:2001
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Now
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Revised by
PublishedISO 6145-7:2018
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