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Main text A regional key comparison on calibration of a line scale, APMP.L-K7 was conducted. KRISS acted as the pilot laboratory, and a total of 15 National Metrology Institutes, (10 from APMP, 3 from EURAMET, 1 from SIM, and 1 from AFRIMETS) have participated in this comparison, where a 500 mm line scale made of low thermal expansion material was circulated during the period from April 2015 to December 2016. This document presents the approved report of the results of this comparison. 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).

Main text This intercomparison is carried out for step height standards with nominal step sizes 8 nm, 18 nm, 88 nm and 10 µm using non-contact measurement methods, with four participating NMIs. Measurement observation from the pilot laboratory exhibit significant stability of step height standards. For each step height standard, the supplementary comparison reference value (SCRV) is determined using weighted mean, followed by calculation of En values for outlier identification. Further the outliers were excluded based upon the Birge Ratio consistency test. Measurement results from all the participating NIMs have been compiled in this report. 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).

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Self-A (Self-calibratable Angle device) rotary encoder can detect some kinds of angle error, not only its encoder scale error, but also the encoder attachment error (e.g. eccentricity error). When rotary table with built-in Self-A encoder rotates only one revolution, inner Self-A rotary encoder can calibrate the own angle error with a high accuracy. However, in the case of the Self-A using the encoder of 36,000 graduation scales, since the angular interval of the calibrated main scales corresponds to 36", it is insufficient for high resolution angular indexing control with high accuracy. Generally, the angle error of electric interpolation signal is estimated to be 1 % of main scale resolution that corresponds to about 0.36" for 36,000 scales encoder. Accordingly, even if Self-A had the ability which can calibrate in the accuracy 0.1", when it was controlling the rotary table using an electric interpolation signal, its total accuracy worsened to about 0.36". For improvement in precise angular-position control, we developed Self-A rotary table which can calibrate the angle signal at high resolution including electric interpolation signals. In this paper, we introduce the performance of the new high resolution Self-A encoder table. It keeps high accuracy and good repeatability in the 360° whole range as well as in the short range of ±1,000".

The key comparison EURAMET.L-K8.2013 on roughness was carried out in the framework of a EURAMET project starting in 2013 and ending in 2015. It involved the participation of 17 National Metrology Institutes from Europe, Asia, South America and Africa representing four regional metrology organisations. Five surface texture standards of different type were circulated and on each of the standards several roughness parameters according to the standard ISO 4287 had to be determined. 32 out of 395 individual results were not consistent with the reference value. After some corrective actions the number of inconsistent results could be reduced to 20, which correspond to about 5% of the total and can statistically be expected. In addition to the material standards, two softgauges were circulated, which allow to test the software of the instruments used in the comparison. The comparison results help to support the calibraton and measurement capabilities (CMCs) of the laboratories involved in the CIPM MRA. 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 diameter measurement of sphere is very important in dimensional metrology. The measurement of diameter is generally carried out by a comparison method or direct method using 1D linear measuring system. The probes touch both sides of the workpiece and the diameter is determined from displacement of the probes. The contact force is generally operated at 1N which yield deformation due to force of approximately 1 μm with uncertainty of ±0.2 μm. This system provides good performance but has a limitation when workpiece is made from soft matter or sensitive to scratch. National Institute of Metrology (Thailand) developed a laser interferometer system which is equipped with reference spherical lens in order to make non-contact radius measurement of spherical objects possible. Radius of completed sphere and partial sphere with radius range from 1 mm up to 50 mm can be measured with accuracy of ±2.4 μm.

Lasers from four national metrological institutes (NMIs) were compared in 2014 as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comité Consultative des Longuers (CCL) in 2007. The absolute frequency of R(127) 11-5 transitions of molecular iodine was measured for these lasers following the technical protocol for CCL-K11. The results of these measurements are compiled in the present report. The comparison reports, as communicated by each participant, are included as appendices. This document constitutes the sixth final report for the ongoing key comparison CCL-K11. 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).

A Michelson interferometer method for determining the variation in length of gauge blocks is presented. This method is based on phase shift interferometer measuring a fringe fraction of the interference fringes on a gauge block measuring surface and its auxiliary plate. The reference standard of measurement is the wavelength of stabilized He-Ne Laser at 633 nm which is traceable to the international standard of the metre. The system was also verified by the 543 nm stabilized He-Ne Laser. The interference fringe patterns are observed by a CCD camera and the images are processed by a Machine Vision system. This make the system run automatically and fulfill. The measurement results were compared with the standard method and they agree with comparable uncertainty.

A regional key comparison, APMP.L-K3 (calibration of angle standards) was held in 2005. Thirteen National Metrology Institutes (NMISA, NMIA, KRISS, NMIJ/ AIST, NMC/ A*STAR, NIMT, SCL, CMS/ ITRI, NPLI, RCM- LIPI, NIM, and NSCL) have participated in this comparison and the measurements were carried out during the period from April 2005 to December 2007. This report describes the measurement results of a 12-sided optical polygon with nominal angles of 30°, and four angle blocks with nominal angles of 5 arc seconds, 5 minutes, 30 minutes and 5 degrees, respectively. 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).

A step gauge is a measurement standard that is used to verify a Coordinate Measuring Machine (CMM). The better the calibration system for the step gauge is, the greater the CMM verification can be. To achieve good step gauge calibration results, step gauge interferometry calibrator has been developed using a four-path laser interferometer system with the implementation of the real-time air refractive index compensation system. The system achieves the measurement uncertainty of 0.7 μm (1=2) at the length of 1 m.

A regional key comparison, APMP.L-K4, was held in 2008. To demonstrate the equivalence of routine calibration services offered by NMIs to clients, participants in this APMP.L-K4 comparison agreed to use the same apparatus and methods as routinely applied to client gauges. There are 14 laboratories from NMIs involved this key comparison, which included CMS/ITRI, NMIJ/AIST, NPL-I, NIMT, Puslit KIM-LIPI, NMISA, MSL, NMIA, NML-SIRIM, VMI, KRISS, SCL, NMC/A*STAR and NSCL. This report describes the measurement results of five diameter standards including two rings and three plugs. The calibrations of this key comparison were carried out by laboratories during the period from May 2008 to November 2010. 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).

Surface roughness calibration services of 16 countries from four metrology regions are compared through measurements of roughness and step height standards. The artefacts circulated include three steps of nominal depths 0.4 µm, 2.4 µm and 10 µm, whereas the roughness sections of both type C and type D profiles have nominal Ra values of 0.2 µm, 0.95 µm, 1.5 µm and 3.1 µm. Two soft-gauges were also circulated for comparison of software independent of hardware. For the steps, parameter d is reported, while for the type C and type D standards and soft-gauges, 14 different roughness parameters are reported between them. Concluding measurements from the pilot in general show good standard stability; however, for some parameters on the artefacts of larger roughness, stability may be considered less certain and this may be an issue in additional outliers in results from the last few laboratories in the schedule. For each parameter, a key comparison reference value (KCRV) is determined using a weighted mean with outliers excluded based on the Birge ratio method until all accepted values form a statistically consistent population. For the five artefacts, out of 35 separate parameters, only ten have good agreement of all submitted results. Where some parameters had to be excluded from the KCRV, some laboratories had consistent problems with particular types of parameter over the different artefacts, while for other laboratories the types of parameters excluded seemed to be random. Comparison of soft-gauge results and artefact results has proven to be inconclusive. 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).

Lasers from eight national metrological institutes (NMIs) were brought to the NIM in Bejing in November 2004 for the APMP.L-K11 regional comparison. The frequency difference between the f components of the R(127) 11-5 transition was measured for these lasers following the Protocol for BIPM.L-K11. The absolute frequencies of three of the participating lasers have been measured with the comb technique either before or after the comparison. The absolute frequencies for the other lasers were then deduced using the three lasers as a link. The results of these measurements are compiled in the present paper. The comparison reports, as communicated by each participant, are included as Appendices. 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 (MRA).