High precision roundness measurement by error separation techniques (EURAMET.L-S30)

Abstract

Main textThe results of the supplementary comparison EURAMET.L-S30 on roundness measurement on two spheres by using error separation techniques are reported. Five National Metrology Institutes from EURAMET participated in this comparison, which lasted nine months from March 2020 to November 2020.Two alumina spheres with diameters of 20 mm and 25 mm, respectively, were circulated. The sphere standards were permanently glued to base supports made of steel and they had to be clamped by each laboratory's own usual methods. The measurand was the roundness defect, measured on the equator. Peak-to-valley roundness deviation (RONt) had to be evaluated with reference to the least squares reference circle (LSCI) and, if possible, to the minimum zone reference circles (MZCI), in accordance with the ISO/TS 12181-1:2011.Each laboratory had to use an error separation technique to remove the contribution of the spindle error. In case of using a multistep technique it was advisable to inform on the number of steps used.All participants successfully demonstrated the validity of the claimed measurement capability. Three of them submitted their approved CMCs and two others smaller values which were shown to be valid when compared to the reference value. One participant did not use an error separation technique, showing, as expected, a higher uncertainty with respect to the rest of the participants but according to its declared CMC.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).