EVS-EN ISO 6145-6:2008

This part of ISO 6145 specifies a method for the continuous production of calibration gas mixtures, containingtwo or more components, from pure gases or other gas mixtures by use of critical orifice systems. By selectionof appropriate combinations of orifices and with the use of pure gases, the volume fraction of the calibrationcomponent in the calibration gas mixture can be varied by a factor of 10^4  . Additionally, it can be changed by afactor of 10^2  by changing the initial pressures in the orifice systems. The uncertainty of the method dependsmainly upon the flow calibration method and the variations in temperature and outlet pressure. The relativeexpanded uncertainty in the volume fraction obtainable for a binary mixture (at a coverage factor of 2) is 3%  .