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).
A few years ago, a 1 N m deadweight torque standard machine was developed, constructed and put into operation at PTB in Germany. Since then, this machine has been used for measurements, but also, investigations of its stability and reproducibility have been carried out. The machine utilizes calibrated stainless-steel masses as weights and a lever made of Invar which is supported by an H-type air bearing. The measurement range starts at 1 mN m. Depending on the weights used, various torque steps are possible. The best expanded (k = 2) relative uncertainty of measurement is 0.01%. In the following, technical details and metrological characteristics of this machine will be given.
As a reference measurement machine for multi-component force and moment sensors of up to six components, a hexapod-structured calibration device was developed at the Physikalisch-Technische Bundesanstalt in 2001. The machine can generate and measure forces of up to 10 kN and moments of up to 1 kN • m. In this paper, the measurement uncertainty budget of the machine is analyzed, beginning with an improved physical model and calculation of sensitivity coefficients using the implicit function theorem and the Monte Carlo method. The main influencing factors for the measurement uncertainty are discussed and suggestions for further reduction of the uncertainty are given.
A torque-generating measuring device in the 1 MN force standard machine of Physikalisch-Technische Bundesanstalt allows combined load conditions to be generated. Superposition is possible in measuring ranges from 20 kN to 1 MN for axial load and from 20 N • m to 2 kN • m for torque. The measurement facility is unique in the world and offers the opportunity to characterize multi-component sensors specifically with regard to their signal crosstalk. The expanded relative measurement uncertainty (k = 2) of the axial force is 2 • 10 −5 . In the following, the technical details of the torque measuring device and the metrological characterization from the modelling to the measurement uncertainty budget will be described. The model provides an expanded relative measurement uncertainty (k = 2) < 3.9 • 10 −4 . The results of comparison measurements will be discussed.
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