Metrology of Torque: State of the Art and Short-Term Development at the cnr-imgc within the frame of european standardization

摘要

Depending on their field of application, torque devices cover a wide span of uncertainties, ranging from the values of a few percent typical of torque wrenches up to those - 10~(-3)÷l0~(-5) -characteristic of high-accuracy transducers. The strong increase in the request for traceability of torque calibrations arising from both industry and research centres is determining all over Europe a noticeable development in the accuracy of primary standards, together with a growth in the efforts aimed at improving harmonisation in determining calibration results and uncertainties. Within this frame, work is in progress at the CNR-IMGC to improve traceability by reducing uncertainties of both primary standards and calibration facilities.Firstly, this paper reports a brief discussion on the main sources of uncertainty for a primary torque standard, with the aim of pointing out its intrinsic limits, particularly with respect to low values. Results obtained from calibrations performed by following two different procedures are presented and discussed, giving prominence to the criteria customers should adopt to make the proper choice to calibrate a device.