The purpose of the CIPM comparison CCM.T-K1 was to compare the measuring capabilities up to 1000 N m of deadweight torque standard machines with supported lever in national metrology institutes. Eight institutes participated, with the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany) acting as pilot laboratory. Two very stable torque transducers with well-known properties were used as travelling standards. The circulation of these transducers started June 2005 and ended in July 2006. According to the technical protocol, torque steps of 500 N m and 1000 N m had to be measured both in clockwise and anticlockwise directions. Corrections had to be applied to the results reported by the participants taking into account the use of different amplifiers, the creep (due to different loading times of the machines) and the environmental conditions in the laboratories (temperature and relative humidity of the ambient air). For each of the transducers, the two torque steps and both senses of direction of the torque vector, a key comparison reference value was calculated.

With one exception at anticlockwise torque, the agreement between the results is very good. The smallest expanded relative uncertainty of the machines stated by the participants is 2 × 10^-5 both for machines with horizontal or vertical axis. The results of the comparison support these uncertainty statements. One participant had problems with anticlockwise torque. These results were not used for the calculation of the corresponding reference values.

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 CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).