Research on the Application of Control Chart Method in the Stability Assessment of Measurement Standard

The establishment and application of control charts are discussed by taking the stability assessment of the metrological standard of the critical flow venturi nozzle method gas flow standard device as an example. Firstly, the range control chart (R chart) is established based on the statistical control limit. Then, the average control chart ($ \overline x $ chart) is established after the confirmation that the R chart is in a controlled state. And the analysis of control charts is further conducted. Starting from the angle of the requirement of the stability assessment, the target control limits of the $ \overline x $ chart are determined. The calculation method of control limits of the $ \overline x $ chart differs from the method stipulated in the JJF 1033-2016 Rule for the Examination of Measurement Standards. This paper determines the target control limits of the mean value control chart from the perspective of the requirements of stability assessment of metrology standards. The control chart can be used to monitor the changes in the standard values provided by the measurement standard and, based on the requirements of the stability assessment, make intuitive and accurate judgments on the stability of the measurement standard, warn of possible quality loss, and ensure the stability of the measurement standard.