Static calibration of calibration devices for torque wrenches : Guideline DKD-R 10-8

In this document, calibration devices for torque wrenches are also referred to as torque wrench calibration devices. This Guideline applies to the calibration of torque wrench calibration devices using torque transfer wrenches as transfer standards. It supports the corresponding requirements of DIN EN ISO 6789. A method for determining the relative measurement uncertainty of these devices is also described. This guideline excludes the use of fixed-length calibration beams and discs as transfer standards. The reason for this is that the determination of the parameter \u27\u27span\u27\u27 for different lever arm lengths is not possible with this type of equipment; hence, it would not be possible to carry out an adequate calibration or to adequately determine the measurement uncertainty. Within the context of this Guideline, torque wrench calibration devices are special torque measuring devices which – because of their design – allow torque to be applied via a torque measuring instrument with lever arm. This Guideline takes into account the different conditions of force introduction and their effect on the calibration item as opposed to those of torque measuring instruments according to DIN 51309. Calibration devices with integrated zero suppression or zero spreading that cannot be switched off during calibration must not be switched off and on again for taring purposes during the entire calibration process after being switched on, unless additional taring during use is required by the manufacturer in the technical documentation. Pursuant to this Guideline, instruments which only allow the detection of peak values are not considered capable of being calibrated. The torque wrench calibration device comprises the entire device - from torque transducer up to and including the display unit. This guideline is applicable from 2020-03-01 onwards; in addition, Guideline DKD-R 3-8 (Edition 09/2018) may be applied until 2022-02-28. If the present Guideline should be used together with Guideline DKD-R 3-7 (Edition 09/2018), i.e. a measuring device calibrated according to DKD-R 10-8 (Edition 02/2020) should form the basis for calibrations according to DKD-R 3-7 (Edition 09/2018), then the hysteresis of the calibration device must be included in the measurement uncertainty budget according to DKD-R 10-8