The results of the inter-RMO key comparison EUROMET.L-K5.2004 on the calibration of a step gauge are reported. Eighteen National Metrology Institutes and one Designated Institute from four different metrological regions all over the world participated in this comparison which lasted three years, from December 2004 to December 2007.A lack of stability was observed through the shifting of some of the inserted gauges. In order to save the comparison and get valuable and useful conclusions, it was agreed to exclude four gauges from calculation and assume that only seven gauges were reasonably stable so as to get the corresponding reference values. It was also agreed to divide the participants into two groups, analyze separately their results and, taking the pilot as the linking laboratory, refer the results to common reference values.The inverse-variance weighted mean was taken as reference value. Due to the significant instability of the step it was also considered an artefact uncertainty. The reported uncertainties ranged from 0.045 µm to 1.2 µm (k = 1). The uncertainty of the artefact ranged from 0.018 µm (for the 20 mm face) to 0.176 µm (for the 400 mm face).The compatibility of all participants for measuring step gauges was demonstrated with the only exception of a participant showing very high systematic (both positive and negative) errors. Five participants communicated higher uncertainties than the corresponding approved CMCs. A set of Recommendations and Actions were agreed therefore.Main text. 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 kcdb.bipm.org/.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).

The accuracy of aperture area measurements is vital to many radiometric and photometric measurements. The Consultative Committee on Photometry and Radiometry (CCPR) undertook an international comparison of the methods by which member laboratories measure the areas of apertures used for radiometry. Nine laboratories measured eight different apertures varying in diameter size, fabrication method, material and edge type. This paper includes a description of the apertures used for the comparison, the results of the comparison categorized by artifact and by laboratory, and a brief discussion of the method used by each laboratory along with its uncertainty budget.Main text. 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 kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Calibration services of five countries from the Sistema Interamericano de Metrología (SIM) region are compared through measurements of surface roughness and step height standards. A surface roughness standard with a nominal roughness average (Ra) value of 0.2 µm, a surface roughness standard with a nominal Ra value of 3 µm and a nominal spatial wavelength of 99 µm, and three step height standards with nominal values of 2.55 µm, 0.38 µm and 0.03 µm are compared. Special attention is paid to the influence of the long wavelength cutoff ratio of the measurements. Results are reported for Ra, maximum height of profile Rz, mean width of profile elements RSm, and step height d, depending on the sample measured. The initial reported results show that the laboratories agree on all of the measurements within their stated and published uncertainties. Observations are then discussed about the definition of Rz, the effect of instrument noise on Rz, the different step height parameters d and Pt, differences between the laboratories in reporting Type A statistical uncertainties, the method for calculating the uncertainty of the reference value, and the importance of accounting for correlations between the reference value and individual lab values when calculating the degrees of equivalence. After corrections and reanalysis the laboratories still agree well considering their stated uncertainties.

The results of the APMP key comparisons on ball plate and hole plate (APMP.L-K6.2007) are reported. Both transfer standards were provided by NMIJ, Japan. The ball plate standard is 532 mm by 532 mm in nominal dimension and 25 spheres are embedded. Thirteen National Metrology Institutes (8 from APMP, 5 from other Regional Metrology Organizations) participated in the ball plate measurement comparison. The hole plate standard is 550 mm by 550 mm in nominal dimension and there are 44 cylindrical holes in it. Nine National Metrology Institutes (5 from APMP, 4 from other Regional Metrology Organizations) participated in the hole plate measurement comparison. The comparison started in May 2006 and finished in October 2008. The participants used different measurement techniques which were used for their routine calibration services. For determining the key comparison reference values, a two-dimensional coordinates-based analysis was performed. The measurement results on the ball plate show good agreement in ten out of thirteen participants. In contrast, those on the hole plate are in agreement for five out of nine participants.Main text. 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 kcdb.bipm.org/.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).

Computed tomography use as a dimensional metrology technique has increased steadily, despite the fact that the uncertainty has been rarely determined and expressed in measurements of production parts. This perception may be attributed in part to a limited way of employing the uncertainty concept. From this perspective, the conceptual integration of the product (and measurement) realization process with the uncertainty approach is first emphazised in this paper. The reasoning behind it is to employ different methods for uncertainty evaluation in a rational sense, where the accuracy required to the uncertainty evaluation process drives the method selection. For critical measurement cases, which can be identified in the proposed concept, the need for advanced correction methods, using master part reference measurements for point-based compensation, is presented, tested and justified for GD&T characteristics.