Estimation of Measurement Uncertainty of Small Circular Features Measured by CMMs

摘要

This paper examines the measurement uncertainty of small circular features as afunction of the sampling strategy, i.e., the number and distribution of measurement points. Specifically, we examine measuring a circular feature using a three-point sampling strategy in which the angular distance between the points varies from widely spaced, 120 degrees, to closely grouped, a few degrees. Both theoretical and experimental results show that the measurements uncertainty is a strong function of the sampling strategy. The uncertainty is shown to vary by four orders of magnitude as a function of the angular distribution of the measurement points. A conceptual framework for theoretically estimating the measuring uncertainty is described and a good agreement with experiment is obtained when the measurements are consistent with the assumptions of the theoretical model.