International Standard
ISO 6145-7:2018
Gas analysis — Preparation of calibration gas mixtures using dynamic methods — Part 7: Thermal mass-flow controllers
Reference number
ISO 6145-7:2018
Версия 3
2018-12
© ISO 2024
International Standard
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Опубликовано (Версия 3, 2018)

ISO 6145-7:2018

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Тезис

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.

Общая информация

  • Текущий статус
     : Опубликовано
    Дата публикации
     : 2018-12
    Этап
    : Рассылка краткого отчета о пересмотре [90.60]
  • Версия
     : 3
  • Технический комитет :
    ISO/TC 158
    ICS :
    71.040.40 
  • RSS обновления

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  2. Интернет-магазин
  3. Каталог стандартов
  4. МКС
  5. 71
  6. 71.040
  7. 71.040.40
  8. ISO 6145-7:2018