The Discussion of Influence of the Inlet Temperature Measurement on the CFVN Calibration

摘要

When the CFVN calibration is carried out, the inlet temperature measurement of the CFVN is detailed described in both "ISO 9300:2005 Measurement of gas flow by means of critical flow Venturi nozzles" and "JJG 620-2008 Critical Flow Venturi Nozzle". But in some cases, the sensing element can not be strictly confirmed to the requirement for some reasons. To explore the influence of the inlet temperature measurement, two different kinds of installation are presented in this paper. Differences between the two installations are the diameter of the sensing element and the location of the sensing element. As the results shown, the inlet temperature measurement has non-negligible influence on the CFVN calibration. According to the comparison, to ensure the accuracy and reliability of traceability, the CFVN should be calibrated under the same installation conditions as that on site. And both the interlaboratory measurement comparison and proficiency testing of CFVN should take the installation impact as an important factor if there are some differences.