Inter-laboratory comparison between NMIJ and KRISS of calibration capabilities for torque measuring devices in the range from 50 N·m to 2 kN·m
An inter-laboratory comparison of the calibration capability for torque measuring devices (TMDs) was conducted between the National Metrology Institute of Japan (NMIJ) in the National Institute of Advanced Industrial Science and Technology (AIST) and the Korea Research Institute of Standards and Science (KRISS). Three high-performance torque transducers having rated capacities of 100 N·m, 1 kN·m, and 2 kN·m, and a bridge calibration unit (BN100A) were used as the transfer devices. The 1 kN·m and 2 kN·m transducers had one bridge, but the 100 N·m transducer had two bridges that acquired data more reliably. An identical indicator/amplifier type (DMP40) owned by each laboratory was used. All of the transducers and BN100A were transferred from NMIJ to KRISS. For the comparison, NMIJ used 1 kN·m and 20 kN·m deadweight torque standard machines (TSMs), and KRISS used a 2 kN·m deadweight TSM. In particular, the capability of the 1 kN·m TSM at NMIJ was examined after some improvements. In the calibration range from 50 N·m to 2 kN·m, relative deviations were less than 3.0 × 10-5 for increasing torques. Sufficiently small deviations were obtained between the calibration results in the two laboratories, as compared with their calibration and measurement capabilities (CMCs), which were 3.5 × 10-5 for the 1 kN·m TSM at NMIJ, 7.0 × 10-5 for the 20 kN·m TSM at NMIJ, and 5.0 × 10-5 for the 2 kN·m TSM at KRISS (as relative expanded uncertainties).
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