Yoshihisa Katase

Improved working efficiency of force standard machine by separating alternative weight stacks

Renovation work has been carried out to separate the 3 kN/500 N dead-weight type force standard machine (DWM) at the National Metrology Institute of Japan. Two loading frames and a common structural frame were newly manufactured. No significant changes were observed in the calibration results of several force transducers before and after the renovation; in some cases, there has even been improvement in terms of repeatability and reproducibility of the calibration results. The renovation has made it possible to operate the two weight stacks simultaneously and to improve the working efficiency of calibration, while maintaining the reliability of the DWMs as the National Force Standards.

Enabling one step loading operation using linkage-weight system of 20 kN force standard machine

The loading frame lifting mechanism of the 20 kN dead-weight type force standard machine was improved to enable the one step loading operation at the first force step. This modification was achieved by adding a reduction gear to amplify the output torque of the motor driving the loading frame. The one step loading operation allows the evaluation of the time-dependent characteristics of force transducers, and also improves the working efficiency. Some force measuring devices showed a little change of sensitivity upon applying the one step loading operation. It was found that the degree of time dependence in the characteristics of the three force measuring devices examined in this study had only a small impact on the measurement uncertainty.

An Estimate of Uncertainty Arising from Loading Speed Differences in Calibrations of Force Measuring Devices

Recently, discussion has arisen on how to estimate uncertainty due to the creep behavior of force measuring devices under calibration. There is a proposal to estimate the uncertainty based on variations of readings arising from loading speed differences between preloading and subsequent calibration cycles. However, in the case of force standard machines with linkage weights, these differences come only from the load duration at each measurement step in the calibration cycle. Though it is a major factor in the uncertainty, this time difference may not be completely representative of the creep effect. An experimental investigation is conducted herein on some other factors which may influence this uncertainty

Sensitivity Evaluation of a Disk-type Torque Transducer Used as a Transfer Device

A torque transfer device is used for international comparison between torque standard machines or for comparison verification between a torque standard machine and torque calibration machine. This experimental study revealed a problem in the case of using a high-precision torque transducer as the transfer device. For a disk-type torque transducer, it was found that a considerable deviation in the torque output sensitivity occurred depending on the dimensions of the adapter flange and the fastening torque of the screw bolts directly connecting the torque transducer to the adapter flanges. A solution is proposed to overcome this difficulty.