Ea-10-14 Rev00

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Publication
Reference

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PURPOSE

This document has been produced by EA to improve harmonisation in determining the calibration results and uncertainties in torque measurements. It provides information on the calibration procedures for torque measuring devices and gives guidance to calibration laboratories to establish a procedure for the expression of the overall uncertaintyof calibration results for torque measuring devices.

Authorship
The publication has been written by EA Committee 2 (Technical Activities), based on a draft of the Task Force « Torque Measurements » of the EA Expert Group « Mechanical Measurements ».

Official language
The text may be translated into other languages as required. The English language version remains the definitive version.Copyright
The copyright of this text is held by EA. The text may not be copied for resale.

Guidance Publications
This document represents a consensus of EA member opinion and preferred practice on how the relevant clauses of the accreditation standards might be applied in the context of the subject matter of this document. The approaches taken are not mandatory and are for the guidance ofaccreditation bodies and their client laboratories. Nevertheless, the document has been produced as a means of promoting a consistent approach to laboratory accreditation amongst EA member bodies, particularly those participating in the EA Multilateral Agreement.

Further information
For further information about this publication, contact your national member of EA. Please check our website forup-to-date information http://european-accreditation.org

CONTENTS

1 SCOPE 4
2 SYMBOLS 4
3 CHARACTERISTICS OF THE TORQUE MEASURING DEVICES 6
4 CALIBRATION OF THE TORQUE MEASURING DEVICE 6
5 DETERMINATION OF THE STANDARD UNCERTAINTY OF MEASUREMENT FOR INCREASING TORQUE 11
6 CALIBRATION CERTIFICATE 14
7 LIST OF REFERENCES 15

APPENDIX A 15
APPENDIX B 16
APPENDIX C 17
APPENDIXD 18
APPENDIX E 19

Scope

1. This guide is generally applicable to torque measuring devices where the torque is obtained by the measurement of the elastic deformation of a body or of a measurand proportional to it.

2. The scope of the calibration provided, should be made clear to the customer and recorded on the certificate when calibrating torque systems, i.e. whether allor some of the following are included: clockwise and/or anti-clockwise, incremental and decremental torque.

3. The uncertainty of measurement is determined in section 5[1], this should include the parameters of the selected scope.

4. This guide applies to the static calibration of torque measuring systems using supported beams or the comparison method with reference transducer andincludes an example for calculation of the uncertainty of measurement. A diagram showing an example of the calibration steps and series is given in Annex D.

5. The torque measuring device is defined as the complete instrument comprising all parts, from the torque transducer to the indicating device.

Symbols

For the purpose of this guide, the symbols given in Table 1 shallapply.

Table 1: Symbols, units and designations

|Symbol |Designation |Unit |
|Mnom |nominal torque (maximum design torque of the device) |N·m |
|MA |minimum torque value of the measuring range|N·m |
|ME |maximum torque value of the measuring range |N·m |
|Mk |applied calibration torque |N·m |
|I0 |indication of torque measuring device of the zero signal prior to load application in...