標準號：DIN EN ISO 6145-6-2008
中文標準名稱：氣體分析.動態容量法制備校準氣體混合物.第6部分:臨界孔
英文標準名稱：Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 6: Critical orifices (ISO 6145-6:2003); English version of DIN EN ISO 6145-6:2008-11
標準類型：G86
發布日期：2008/11/1 12:00:00
實施日期：1999/12/31 12:00:00
中國標準分類號：G86
國際標準分類號：71.040.40
引用標準：ISO 6143;ISO 6145-1
適用范圍：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 104. Additionally, it can be changed by afactor of 102 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 %.It pre-mixed gases are used instead of pure gases, much lower volume fractions can be obtained (seeAnnex A). The mass flow rates or volume flow rates, from which the mass or volume fractions are determined,can be calculated and can be independently measured by a suitable method given in ISO 6145 1.The merits of the method are that multi-component mixtures can be prepared as readily as binary mixtures if theappropriate number of orifices is utilized, and that a large quantity of calibration gas mixture can be prepared ona continuous basis. The range of flow rates can be from several millilitres per minute to approximately 10 Fmin.Although particularly applicable to preparation of gas mixtures at barometric pressure, the method also providesa means of preparation of calibration gas mixtures at pressures above barometric pressure.Annex B gives practical hints on the use of the method.