Uncertainty Propagation for Force Calibration Systems

Measurement Uncertainty Pyramid

by H. Zumbrun and A. Zeinali

There are several labs operating throughout the world, whom do not follow a designated guideline for calculating measurement uncertainty for force calibrations. Realizing the need for a guidance document, Morehouse decided to draft this document explaining how to calculate measurement uncertainty and how uncertainty propagation for force calibration systems works. Calibration and utilization of measurement instruments will imply some level of uncertainty. As an instrument calibration is traced back to SI units, a higher number of intermediate calibration stages results in higher levels of measurement uncertainty (Figure 1). In other words, uncertainty of the unit under test is typically higher than the standard with which it was calibrated. It is not possible for the expanded measurement uncertainty of the unit being calibrated to be less than the machine or force measuring device that is used to calibrate the unit itself. This paper describes the propagation of uncertainties using Calibration and Measurement Capability (CMC) for force measurement instruments through the traceability chain to SI units. For the instrument users who require some minimum level of expanded uncertainty, this paper provides information on what level of calibration is needed for their reference standards. Read Full Paper (PDF)