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.
展开▼
