Abstract. An alternative method to using strain gauges to measure FT (please see Appendix A for a list of definitions) and TM under a static multi-component load by using a hinge flexure (also called measurement flexure or MF) is presented. Its usage in the 5 MN m torque standard machine (TSM) at the Physikalisch-Technische Bundesanstalt (PTB) to detect calibration torque moment shunts is described. The working principle consists of a displacement measurement by an interferometer and the determination of the MF stiffness in a special CSU. Essential measurement uncertainty influences, such as stiffness determination and measurement conditions, are discussed and quantified. The measurement uncertainty budget for this measurement principle is presented. A FE validation for the MF is discussed.

<p class="Abstract">To verify all technical aspects of wind turbines, more and more nacelle test benches have come into operation. One crucial parameter is the initiated torque in the nacelles, which amounts to several MN·m. So far, no traceable calibration to national standards has been performed in such test benches. The paper will show calibration possibilities which already exist and also show future prospects.</p>

A measurement flexure calibration set-up is presented in this paper. The measurement flexures under test are part of a new 5 MN · m standard torque machine measurement system at the PTB. The calibration set-up can create transversal forces up to 200 N and bending moments up to 100 N · m and respectively up to 150 N · m torque moments simultaneously. The measurement uncertainty budget of the set-up is investigated in a theoretical analysis.

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.

The paper describes mechanical influences which disturb a sinusoidal force calibration and hence have an influence on measurement uncertainty. The measurements are based on the application of a scanning vibrometer and the use of triaxial accelerometers. The measuring of many acceleration points on the top mass of the transducer makes it possible to obtain acceleration distributions from which a standard deviation can be derived; the triaxial accelerometer allows the observance of certain effects, like rocking modes, or other problems related to specific excitation frequencies of the force transducer. Both measurements can be related to each other. The rocking effects are discussed with FEM model calculations.