KEY COMPARISON: Final report on CCL-K3: Calibration of angle standards

This report is prepared by the Discussion Group 3 (DG3) for angle standards under the CCL Working Group on Dimensional Metrology (WGDM). It describes the results of Key Comparison CCL-K3 concerning measurements of a chrome carbide twelve-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. The majority of the thirteen participants (all from national metrology institutes) used a Moore or Heidenhain index table to position the test object (polygon/angle blocks) to the nominal angle. A few laboratories used other devices such as a ring laser or a measurement system designed in-house. To measure the deviation from the nominal angles, most laboratories used autocollimators, and only two laboratories used laser interferometers. The reported uncertainties for the polygon ranged from 8 msec to 100 msec (k = 1). For the angle blocks the uncertainties ranged from 11.5 msec to 735 msec (k = 1). The key comparison reference value (KCRV) for the polygon was determined using all 156 measurements reported by the thirteen participants. For the four angle blocks, a total of 51 angle measurements were reported. The KCRVs were calculated from only 47 measurement results due to the omission of four measurements that showed En values larger than one. The results of the polygon are consistent to a very high degree of accuracy. The angle blocks, with the exception of the four results that were omitted, were consistent although not to the same degree of accuracy as for the polygon. 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).