Comparison of angle standards with the aid of a high-resolution angle encoder

Germany's National Metrology Institute the Physikalisch-Technische Bundesanstalt (PTB) and the DR. JOHANNES HEIDENHAIN GmbH (HEIDENHAIN) have conducted and compared measurements using their primary angle standards, which are realized as angle comparators of similar design. A high-resolution digital angle encoder served as the transfer standard for this comparison. Calibrations of the transfer standard by the two angle comparators resulted in an agreement of +/- 0.002 ''. The result proved to be consistent with the measurement uncertainties that the participants attributed to their calibration. PTB succeeded, using an additional comparison with a self-calibration method, in improving the measurement uncertainty of its comparator by a factor of 2.5 to 0.002 '' (k = 2). The results of both participants demonstrated the suitability of the digital angle encoder as transfer standard for angle measurement comparisons aimed at uncertainties of a few thousandths of an arcsecond. (C) 2009 Elsevier Inc. All rights reserved.