Project 887 Force Uncertainty Guide. Andy Knott, NPL EUROMET TC-M Lensbury, Teddington, United Kingdom 1 March 2007

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1 Project 887 Force Uncertainty Guide Andy Knott, NPL EUROMET TC-M Lensbury, Teddington, United Kingdom 1 March 2007

2 Background EA-10/04 (EAL-G22) EUROMET Calibration Guide EM/cg/04.01/p

3 Participants SMD (BE) PTB (DE) CEM (ES) MIKES (FI) LNE (FR) NPL (GB) EIM (GR) INRIM (IT) SP (SE) UME (TR)

4 Torino Actions 1) The present document only covers the calibration of force measuring devices to EN (now superseded by ISO 376) - i.e. the Standard which gives traceability to force measurements in materials testing - but force measurements are made in many other areas. Different countries have developed their own Standards for the calibration of force measuring devices to meet traceability needs in these other areas (e.g. BS 8422 in the UK and DKD-R 3-3 in Germany), and the EUROMET document should give some guidance on uncertainty calculations for these calibrations too. The question of the whether the uncertainty associated with continuous calibrations (such as DKD-R 3-9) should be addressed in the document also needs to be considered. ACTION: All participants to send me details of any national standards / documents / publications addressing force calibrations - we can then see how much extra effort would be involved in broadening the scope of the document to address these, either in detail (it was suggested that this would involve a major amount of work) or in more general terms.

5 Torino Actions continued 2) The present document makes no mention of the uncertainty associated with the subsequent measurements made by the force measuring device - for the materials testing area, this is covered to some degree by ISO 's uncertainty annex, but it was felt that some guidance on uncertainty calculations for other applications might also prove useful. ACTION: Scope of document to be extended to include guidance on the uncertainty associated with the use of the force measuring device. 3) An uncertainty annex is currently being developed for ISO 376, within ISO/TC 164/SC 1/WG 3 (chaired by Rolf), and it would be appropriate to wait for the conclusion of this work before amending the relevant sections of our EUROMET document. It is hoped that work on the ISO 376 Annex will be completed in Seoul in September, prior to the SC 1 meeting on 27 September. ACTION: Relevant sections not to be amended until after the ISO meeting in Seoul.

6 Torino Actions continued 4) It was suggested that the document would benefit from a section on how to calculate the uncertainty of a machine by a high-accuracy direct comparison against another machine of lower uncertainty (not necessarily a national standard). ACTION: All participants to review the existing document and suggest areas for improvement (including draft text for proposed new sections).

7 EA 10/04 Contents Uncertainty Of Calibration Results In Force Measurements Types of force calibration machine bmc of force calibration machines plan to determine uncertainty of reference value (from calibration of transfer standard in national force standard machine) calculation of bmc Uncertainty of EN calibration results

8 EM/cg/04.01/p Proposed Contents Uncertainty Of Force Measurements Types of force calibration machine bmc of force calibration machines plan to determine uncertainty of reference value (from calibration of transfer standard in national force standard, or other higher accuracy, machine) calculation of bmc

9 EM/cg/04.01/p Proposed Contents continued Uncertainty Of Force Measurements continued Uncertainty of calibration results ISO 376 (use proposed Annex (.doc /.pdf) Report / Resolutions) other static standards (e.g. BS 8422, DKD-R 3-3) continuous calibrations (e.g. DKD-R 3-9) dynamic calibrations Uncertainty of subsequent force measurements ISO (use existing Annex) other force measurement applications

10 Discussion EA 10/04 / EAL G22.doc /.pdf Draft EUROMET Calibration Guide EM/cg/04.01/p.doc /.pdf