ISO 6145-7:2018
2018-12
Resumen
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.
If this method is employed for preparation of calibration gas mixtures the optimum performance is as follows: the relative expanded measurement uncertainty U, obtained by multiplying the 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 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.
NOTE Gas blending systems, based upon thermal mass-flow controllers, and some including the facility of computerization and automatic control, are commercially available.
Informaciones generales
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Estado: PublicadoFecha de publicación: 2018-12Etapa: Norma Internacional confirmada [90.93]
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Edición: 3Número de páginas: 14
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Comité Técnico :ISO/TC 158ICS :71.040.40
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Ciclo de vida
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Anteriormente
RetiradaISO 6145-7:2009
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Ahora
