In traditional calibration, we must use a torque standard machine which measuring range is larger than that of the calibrated torque transducer. With the rapidly development of power machinery, its torque has been larger than 100 kN·m now, but it is difficult to establish corresponding torque standard machine in so large range. We developed a similarity method in calibrating those super-large range clamping ring type torque transducer in 30 kN·m torque standard machine. Testing a series of specimens with same method, similarity in geometry, time and kinetic, but in different similarity rates, we obtain the largest similarity rates in 12.5 with uncertainty ≤ 0.5%. It means that we can calibrate a 375 kN·m clamping ring type torque transducer on a 30 kN·m torque standard machine with uncertainty ≤ 0.5%. In the same reason, with the similarity method, larger torque transducer can be calibration. The theorem, testing, data processing, uncertainty analysis are described with detail in this paper.

In the metrology of the mechanical quantities of force and torque, standard machines are used that allow these components to be generated in a given direction. For force in most cases this is the vertical, for torque both the horizontal or the vertical directions are in use. In contrast to this realization, for some applications it is necessary to generate forces or moments in arbitrary directions. Moreover, the standard machines generate only one main component and in addition small disturbing components. But it is often desired to have a superposition of forces and moments without a main component.
The present work describes a new method of generating and measuring arbitrary directed forces and moments using a set of six drives on one side of the machine and six force transducers on the other. Both the drives and the force transducers are arranged in a hexapod structure. A theoretical overview is followed by a description of the general design of the machine. Some optimization procedures show the dependence on the chosen geometry of the load decomposition into the six forces. Due to the limited stiffness of the transducers and the structural parts of the machine, the set of equations describing the system must be found by a process of iteration. Some considerations relating to the practical realization conclude the paper.

The uncertainty of each component in the developed deadweight torque standard machine of rated capacity 1 kN·m has been evaluated at the National Metrological Institute of Japan (NMIJ). For estimating Best Measurement Capability, the following evaluations had remained: actual moment-arm length during torque calibration, influence of measurement axis misalignment due to the coupling condition. Therefore, the actual moment-arm length was estimated by measuring the temperature distribution of the moment-arm in the environment of the torque calibration room. In addition, the length variation of the moment-arm under deadweight loading was measured with a laser interferometer system. Moreover, the difference in the output of the torque transducer was observed for three connection methods when mounting the torque transducer on the torque standard machine. Consequently, the Best Measurement Capability in the torque standard machine was brought within ±25 ppm as the relative expanded uncertainty for the calibration range form 5 N·m to 1 kN·m.

Calibrating weight sets creates some unique challenges to the metrologist. Performance and reliability of the calibration oppose its productivity. A calibration of a weight set, also called a dissemination, requires manual interventions by the operator, even if it is performed on a mass comparator with a turntable. Sometimes, a comparator does not offer enough room to accommodate an entire group of weights; then the use of custom auxiliary weights may be required. Besides, the threat of confounding weights is omnipresent. Recently, a new generation of computer controlled comparators, particularly designed for the calibration of weight sets, has become available. This equipment automatically executes all steps involved in disseminations, including the moving of the weights and the necessary comparisons, requiring neither manual intervention by the operator, nor custom auxiliary weights. This not only avoids the introduction of excess uncertainty by the operator, but also improves the productivity of the dissemination, generating more throughput in shorter time.

As measurement instrument the weighing instrument has a very good measurement accuracy compared to some other measurements in processes. To know the characters of the weighing instrument the user must be able to evaluate it. The calibration is one method to show this working capacity of weighing instruments. The user must be able to define the values for permissible error of indication as well as the needed uncertainty of the calibration. The practice has shown that in the most cases it is adequate to indicate these values as scale intervals and it is as well a very pragmatic way to estimate the capability of weighing instruments. How can the user argue these values without careful analysis? The manufacturers give technical data of weighing instruments and the user can make good use of it. In most cases these values can be reached only in the best environmental circumstances even lower accuracy were sufficient. The analysis over some thousand-calibration results gives indication to evaluate the needed calibration uncertainty of weighing instruments in practice.