European comparison of long gauge blocks

A EUROMET comparison of two long gauge blocks was organized by the Physikalisch-Technische Bundesanstalt. Nine EUROMET laboratories had agreed to participate in this comparison. One of them withdrew its participation during the course of calibrations. The measurements started in autumn 1993 and ended in January 1995. The gauge blocks had nominal lengths of 600 mm and 1000 mm. The latter gauge block was damaged shortly before the end of the project and was replaced by one of 900 mm nominal length. The measurement items were the central length, the variation in length, and - if possible - the determination of the coefficient of thermal expansion. The measurements of the central length agree roughly within ± 0,05 μm and the estimated values of the uncertainty overlap. The measured values of the variation in length fluctuate by a few hundred nanometres. The agreement of the coefficient of thermal expansion is satisfactory.