Establishment of torque realisation up to 5 kN·m with a new design of the torque standard machine

Nittaya Arksonnarong, Nattapon Saenkhum, Pramann Chantaraksa, Tassanai Sanponpute


A Torque Standard Machine (TSM) with a rated capacity of 5 kN·m was designed and constructed by the Torque Laboratory, National Institute of Metrology (Thailand), NIMT. The machine had initially used a flexure bearing as a fulcrum. It had been developed based on the research of a 10 N·m suspended fulcrum TSM. However, the bearing structure was changed to a combination of eight elastic hinges in order to withstand larger cross-forces for providing greater strength and providing a shorter stabilising time, consuming the lever arm’s swing. With a three-column weightlifting system, the machine provides five measuring ranges ranging from 100 N·m to 5,000 N·m in the same set of stacked weights.

The measurement results showed the sensitivity of the fulcrum within ± 0.005 N·m from 10 % to 100 % of the measurement range. The sensitivity of the fulcrum is one of the main sources of the uncertainty evaluation of the torque measurement. The Calibration and Measurement Capabilities (CMCs) of the torque measurement were 0.01 % (k=2) in the measurement range from 500 N·m to 5,000 N·m. To confirm the capability of the measurement, an informal comparison with Physikalisch-Technische Bundesanstalt (PTB) was conducted. The results were satisfactory, with the |En| less than 1.

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