RECALIBRATION OF THE MOMENT ARM LENGTH OF A 10 N·m DEAD WEIGHT TORQUE STANDARD MACHINE AND COMPARISON WITH A 1 kN·m DEAD WEIGHT TORQUE STANDARD MACHINE

Atsuhiro Nishino, Koji Ogushi, Kazunaga Ueda

Abstract

A 10 N·m dead weight torque standard machine (10- N·m-DWTSM) has been developed and evaluated since 2006. The main parts of the moment arm in the 10-N·m-DWTSM are made of low thermal-expansion alloy (Super Invar). It is known that parts made of Super Invar vary in length with age. In this study, the moment arm length was recalibrated using a 3D coordinate measurement machine. As a result, the moment arm length was found to have lengthened by an average of 6.3 µm in five years. Also, the relative expanded uncertainty of torque, <i>W</i>_tsm, realized by the 10-N·m-DWTSM was revaluated in a range from 0.1 N·m to 10 N·m, and <i>W</i>_tsm was 7.0 × 10^-5, with the coverage factor <i>k</i> being equal to 2. In addition, the 10-N·m-DWTSM was compared with the 1-kN·m-DWTSM at NMIJ/AIST by using torque measuring devices after estimating <i>W</i>_tsm realized by the 10-N·m-DWTSM. Equivalence between the two DWTSMs was confirmed within the uncertainty of comparison.

Keywords

torque, uncertainty, Super Invar, secular length change, small torque, intra-comparison

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IMEKO-WC-2012-TC3-O31.pdf

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IMEKO TC

TC3 - Measurement of Force, Mass, Torque, and Gravity

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