Application of Shewhart control statistics to RF/microwave measurements

Accurate and consistent measurement data is paramount to the success of any research and development and design organization. A key component of managing a complex laboratory environment is the strategy selected to monitor the measurement systems used for data collection. Issues with repeatability and reproducibility are often a result of unintentional changes to the system configuration that go unnoticed by system operators. Tracking and statistically analyzing the output of a measurement system over time ensures that inaccuracies do not negatively impact analysis. This paper describes a MATLAB™ based tool developed using Shewhart control charts to monitor the performance of a measurement system over time. Collected data are plotted vs. time against an average value determined from a baseline data set. The main feature of the control chart is the ability to apply statistical control limits to the data set that will inform the measurement system operator when the output of the system is unacceptable.