Gas analysis -- Preparation of calibration gas mixtures using dynamic volumetric methods -- Part 7: Thermal mass-flow controllers
This standard was last reviewed and confirmed* in 2014.
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.
Document published on: 2009-04 Edition: 2 (Monolingual) ICS: 71.040.40 Status: Published Stage: 90.92 (2016-07-13) TC/SC: ISO/TC 158 Number of Pages: 15
Revised by: ISO/NP 6145-7
Revises: ISO 6145-7:2001
No corrigenda or amendments available