Statistical evaluation of calibration factor drift of the power sensor and calibration interval

This paper describes the determination of drift specification based on the data collection from the statistical process control (SPC) in the power sensor test stations. Linear regression analysis on check standards is used for the determination of long-term drift. Working standards traceable to the NIST also contributed to the total amount of drift in the measurement system. It is important to estimate the level of significance of the traceable standards. An empirical study based on the multiple measurements by the NIST was conducted for the stability test. This study compares the long-term drift to the interval of calibration accuracy. The results show a good agreement.