气体动态稀释装置的可靠性评价

基于质量流量控制器(MFC)搭建了一套稀释装置,并通过高精度甲烷光谱仪验证了该装置的可靠性。试验结果表明,稀释比为0.01～0.02时,理论稀释浓度的相对误差不超过±4%;稀释比为0.04～0.1时,理论稀释浓度的相对误差在±0.5%以内。因此,稀释比很小时稀释装置的准确性欠佳。MFC上游输入气体压力变化对其输出气体流量存在影响,当输入压力在0.2～0.6MPa范围内变化时,MFC输出气体流量变化极差不超过1%,由此导致稀释装置输出的标准气体浓度的变化不超过1%。使用稀释装置制备标准气体时,优先设定MFC在满量程10%以上的范围内工作,以保证稀释装置的可靠性。

Reliability Evaluation of Gas Dynamic Dilution Device

A dilution device was built based on mass flow controllers (MFC), and a high-precision CH4 spectrometer was used to evaluate the reliability of the gas dilution device. Experimental results showed that when the dilution ratio was 0.01～0.02, the relative error of the theoretical concentration of gas mixture produced by the device was not more than ±4%, and when the dilution ratio was 0.04～0.1, the relative error was within±0.5%. The accuracy of the dilution device was not so good when the dilution ratio was very small. The change of input gas pressure upstream of MFC had influence on its output gas flow. When the input pressure changed in the range of 0.2 ~ 0.6MPa, the variation range of MFC output gas flow was not more than 1%, resulting in the variation of standard gas concentration output by the dilution device was not more than 1%. When the input gas pressure changed in the range of (2～6)bar, the variation range of MFC output gas flow was not more than 1%. The input gas pressure variation could interfere with the diluted gas concentration generated by the dilution device, of which the influence was less than 1%. When using the dilution device to prepare standard gas, it is preferable to set the MFC in the range above 10% of its full scale, so as to ensure the reliability of the dilution device.