Tiêu chuẩn iso 06789 2 2017

INTERNATIONAL STANDARD ISO 6789-2 First edition 2017-02 Assembly tools for screws and nuts — Hand torque tools — Part 2: Requirements for calibration and determination of measurement uncertainty Outils de manoeuvre pour vis et écrous — Outils dynamométriques commande manuelle — Partie 2: Exigences d’étalonnage et détermination de l’incertitude de mesure Reference number ISO 6789-2:2017(E) © ISO 2017 ISO 6789-2:2017(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2017, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2017 – All rights reserved ISO 6789-2:2017(E) Contents Page Foreword iv Introduction v Scope Normative references Terms, definitions and symbols 3.1 Terms and definitions 3.2 Symbols, designations and units Requirements for calibration 4.1 Calibration during use 4.2 Calibration method 4.3 Calibration system Measurement error 5.1 Calculation of the relative measurement error 5.2 Exemplary calculations o f the relative measurement error 5.2.1 Example 5.2.2 Example 6 Sources of uncertainty 6.1 General 6.2 Evaluation o f Type B uncertainties due to the torque tool 6.2.1 Scale, dial or display resolution, r 6.2.2 Variation due to the reproducibility o f the torque tool, b rep 10 6.3 6.2.3 Variation due to the interface between the torque tool and the calibration system 11 6.2.4 Variation due to the variation of the force loading point, bl 12 Evaluation o f Type A uncertainty due to the torque tool 13 6.3.1 General 13 6.3.2 Variation due to the repeatability o f the torque tool, bre 13 Determination of the calibration result 13 7.1 Determination o f the relative standard measurement uncertainty, w 7.2 Determination o f the relative expanded measurement uncertainty, W 7.3 Determination o f the relative measurement uncertainty interval, W’ Calibration certificate 15 Annex A (informative) Calculation example for an indicating torque tool (Type I) 16 Annex B (informative) Calculation example for a setting torque tool (Type II) 25 Annex C (normative) Minimum requirements for the calibration of the torque measurement device and the estimation of its measurement uncertainty 34 Bibliography 41 © ISO 2017 – All rights reserved iii ISO 6789-2:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the voluntary nature o f standards, the meaning o f ISO specific terms and expressions related to formity assessment, as well as in formation about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso org/iso/foreword html This document was prepared by Technical Committee ISO/TC 29, Small tools, Subcommittee SC 10, Assembly tools for screws and nuts, pliers and nippers This first edition o f ISO 6789-2, together with ISO 6789-1, cancels and replaces ISO 6789:2003 which has been technically revised with changes as follows a) ISO 6789:2003 has been divided into two parts ISO 6789:2003 has become ISO 6789-1 which specifies the requirements for design and manu facture including the content o f a declaration o f formance This document specifies the requirements for traceable certificates o f calibration It includes a method for calculation of uncertainties and provides a method for calibration of the torque measurement device used for calibrating hand torque tools b) This document includes detailed methods for calculation o f the uncertainty budget which shall be performed for each individual tool c) This document includes example calculations that are provided for di fferent types o f torque tool d) Annex C provides requirements for calibrating the torque measurement device where the calibration laboratory does not utilize a national standard giving such requirements A list of all parts in the ISO 6789 series can be found on the ISO website iv © ISO 2017 – All rights reserved ISO 6789-2 :2 017(E) Introduction The revision of ISO 6789:2003 has been designed to achieve the following improvements ISO 6789 has been split to provide two levels of documentation It recognizes the different needs of different users of the standard ISO 6789-1 continues to provide designers and manufacturers with relevant minimum requirements for the development, production and documentation of hand torque tools This document provides detailed methods for calculation of uncertainties and requirements for calibrations This will allow users o f calibration services to more easily compare the calibrations from di fferent laboratories Additionally, minimum requirements for the calibration o f torque measurement devices are described in Annex C The purpose o f this document is to define the requirements for a calibration in which the sources o f uncertainty are evaluated and used to define the range o f values within which the readings probably fall Additional uncertainties may exist in the use o f the torque tool The evaluation o f uncertainties for each individual tool is time-consuming and where there are su fficient data to estimate the Type B uncertainty components by statistical means, it is acceptable to use these values for a given model o f torque tool, providing that the uncertainty components are subject to periodic review © ISO 2017 – All rights reserved v INTERNATIONAL STANDARD ISO 6789-2:2017(E) Assembly tools for screws and nuts — Hand torque tools — Part 2: Requirements for calibration and determination of measurement uncertainty Scope T h i s c ument s p e c i fie s the me tho d for the c a l ibration o f h and torque to ol s and de s crib e s the me tho d of calculation of measurement uncertainties for the calibration T h i s c u ment s p e c i fie s the m i n i mu m re qui rements device where the relative me as u rement u ncer ta i nty for the c a l ibration o f the torque me as u rement i nter va l, W´md , is no t a l re ady provide d by a trace able c a l ibration cer ti fic ate I S O 678 i s appl ic able for the s tep b y s tep (s tatic) and conti nuou s (quas i- s tatic) c a l ibration o f torque me as u rement device s , the torque o f wh ich i s defi ne d b y me as u ri ng o f the ela s tic form ch ange o f a de formab le b o dy or a me as u re d vari able wh ich i s i n prop or tion to the torque T h i s c u ment appl ie s to h and torque to ol s wh ich are cla s s i fie d a s i nd ic ati ng torque to ol s ( Typ e I ) and s e tti ng torque to ol s ( Typ e I I ) NO TE H a nd torque to o l s covere d b y th i s c u ment a re the one s identi fie d i n I S O 170 : 0 b y re ference nu mb ers 0 1 , 0 1 a nd 0 , 0 a nd 0 14 , 0 I S O 170 i s c u r rentl y under revision In the next edition, torque tools will be moved to an own clause, and with this change the reference numbers will also change and additional reference numbers will be added Normative references T he fol lowi ng c u ments are re ferre d to i n the tex t i n s uch a way th at s ome or a l l o f thei r content s titute s re qu i rements o f th i s c u ment For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c ument (i nclud i ng a ny amend ments) appl ie s ISO 6789-1:2017, Assembly tools for screws and nut — Hand torque tools — Part 1: Requirements and methods for design conformance testing and quality conformance testing: minimum requirements for declaration of conformance ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories Terms, definitions and symbols ISO 6789-1 f ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia org/ — ISO Online browsing platform: available at http://www.iso org/obp For the purp o s e s o f th i s cument, the term s and defi nition s given i n © ISO 2017 – All rights reserved and the ol lowi ng apply ISO 6789-2:2017(E) 3.1 Terms and definitions 3.1.1 Type A evaluation (of uncertainty) method o f evaluation o f uncertainty by the statistical analysis o f series o f observations Note to entry: These data are taken directly from the measurements obtained during calibration o f each torque tool and cannot be prepared in advance [SOURCE: ISO/IEC Guide 98-3:2008, 2.3.2, modified — Note to entry has been added.] 3.1.2 Type B evaluation (of uncertainty) method o f evaluation o f uncertainty by means other than the statistical analysis o f series o f observations [SOURCE: ISO/IEC Guide 98-3:2008, 2.3.3] 3.1.3 calibration system combination o f a measurement device and the loading system for application o f torque that acts as the measurement standard for the hand torque tool Note to entry: A calibration system can also be used as a torque measurement system as defined in ISO 6789-1 3.1.4 measurement device working measurement standard provided either mechanically or by an electronic torque transducer and display Note to entry: A measurement device can also be re ferred to as a torque measurement device as defined in ISO 6789-1 3.1.5 reference measurement standard measurement standard designated for the calibration of other measurement standards for quantities of a given kind in a given organization or at a given location [SOURCE: ISO Guide 99:2007, 5.6] 3.1.6 measurement error measured quantity value minus a re ference quantity value [SOURCE: ISO/IEC Guide 99:2007, 2.16, modified — Notes and to entry have been omitted.] 3.2 Symbols, designations and units The designations used in this document are indicated in Table Table — Symbols, designations and units Symbol as as be b ref,e b ep Designation Calculated relative measurement error of the torque tool for the calibration torque Mean value of the relative measurement error at each calibration torque Stated measurement error of the measurement device Measurement error of the reference at the calibration torque Stated relative measurement error of the measurement device NOTE While N∙m is the unit commonly used, the output signal can be detected in various units, e.g voltage Unit % % N∙m N∙m % © ISO 2017 – All rights reserved ISO 6789-2:2 017(E) Table (continued) Symbol b ref,ep b int bl b od b re b md,re b rep b md,rep bz I I0 Iz k r rmd TA TE Tmin w wint wl wmd wmd,c wmd,t wmd,d wod wr wmd,r wre wmd,re wrep wmd,rep wmd,z Designation Relative measurement error of the reference at the calibration torque Variation due to geometric effects of the interface between the output drive of the Unit % torque tool and the calibration system N∙m Variation due to the variation of the force loading point Variation due to geometric effects of the output drive of the torque tool Variation due to the repeatability o f the torque tool Variation due to the repeatability o f the measurement device in the same mounting N∙m N∙m N∙m position N∙m Variation due to the reproducibility o f the torque tool (Type I and Type II Classes A, D and G only) Variation due to the reproducibility o f the measurement device in di fferent mounting N∙m Measurement hysteresis error o f the zero signal a fter loading N∙m N∙m positions Indicated value of measurement device without zero-value compensation Indicated value of the zero signal 30 s after preload and prior to load in mounting position Indicated value of the zero signal 30 s after unloading Coverage factor k = applied to the relative measurement uncertainty to achieve a confidence level o f approximately 95 % Resolution o f the display (Type I and Type II Classes A, D and G only) Resolution o f the measurement device display Minimum limit of measuring range of the measurement device Maximum limit of measuring range of the measurement device Minimum limit value o f the measurement range o f the torque tool declared by the manufacturer Relative standard measurement uncertainty o f the torque tool at the calibration torque Component of w due to geometric effects of the interface between the output drive o f the torque tool and the calibration system Component of w due to the length variation of the force loading point Relative standard measurement uncertainty o f the measurement device at the calibration torque Combined relative standard measurement uncertainty o f the measurement device Relative standard measurement uncertainty o f the measurement device transducer Relative standard measurement uncertainty o f the measurement device display Component of w due to geometric effects of the output drive of the torque tool Relative standard measurement uncertainty due to resolution o f the display o f the torque tool (Type I and Type II Classes A, D and G only) Relative standard measurement uncertainty due to resolution o f the measurement device display Component of w due to repeatability o f the torque tool Component of wmd due to repeatability o f the measurement device Component of w due to reproducibility of the torque tool (Type I and Type II Classes A, D and G only) Component of wmd due to reproducibility o f the measurement device Component of wmd due to the measurement hysteresis error o f the zero signal o f the measurement device N∙m N∙m N∙m — N∙m N∙m N∙m N∙m N∙m % % % % % % % % % % % % % % % NOTE While N∙m is the unit commonly used, the output signal can be detected in various units, e.g voltage © ISO 2017 – All rights reserved ISO 6789-2 :2017(E) Table (continued) Symbol Designation W Relative expanded measurement uncertainty of the torque tool at the calibration torque Relative measurement uncertainty interval o f the torque tool at the calibration torque Relative expanded measurement uncertainty o f the measurement device at the % % % Relative measurement uncertainty interval o f the measurement device at the % % % W′ Wmd W′md Unit calibration torque calibration torque W′ref Relative expanded measurement uncertainty o f the re ference measurement standard Relative measurement uncertainty interval o f the re ference measurement standard Xa Target indicated, set or nominal value depending on the type and class of the torque tool Wref X Xmin Xmax Xr Xr Xref Indicated value of measurement device with zero-value compensation Re ference value determined by the measurement device N∙m N∙m N∙m N∙m N∙m Mean re ference value determined by the measurement device N∙m Re ference value determined by the re ference device N∙m Minimum value of X observed during different mounting positions Maximum value of X observed during different mounting positions NOTE While N∙m is the unit commonly used, the output signal can be detected in various units, e.g voltage 4.1 Requirements for calibration Calibration during use If the user utilizes procedures for the control of test devices, torque tools shall be included in these procedures The interval between calibrations shall be chosen on the basis of the factors of operation such as required maximum permissible measurement error, frequency o f use, typical load during operation as well as ambient conditions during operation and storage conditions The interval shall be adapted according to the procedures specified for the control o f test devices and by evaluating the results gained during successive calibrations I f the user does not utilize a control procedure, a period o f 12 months, or 000 cycles, whichever occurs first, may be taken as de fault values for the interval between calibrations The interval starts with the first use o f the torque tool Shorter interval between calibrations may be used i f required by the user, their customer or by legislation The torque tool shall be calibrated when it has been subjected to an overload greater than the values given in ISO 6789-1:2017, 5.1.6, a fter repair, or a fter any improper handling which might influence the torque tool per formance and the fulfilment o f the quality formance requirements 4.2 Calibration method The method for the calibration of the torque tools shall be in accordance with the measurement method o f ISO 6789-1:2017, Clause Additionally, the requirement for the torque measurement device defined in ISO 6789-1:2017, 6.1 is replaced by 4.3 4.3 Calibration system The calibration system shall be chosen to be suitable for the measurement o f the specified range o f the torque tool © ISO 2017 – All rights reserved ISO 6789-2 :2017(E) Table B.5 Reference value Target value Xr Tmin N∙m N∙m Position (0°) Position (90°) X r = 59 , 861 X r = 59 , 262 62,480 59,360 59,550 59,330 59,260 59,210 59,790 60,640 59,430 59,560 60 Position (180°) 60,890 58,920 59,780 58,850 59,430 59,180 58,970 58,980 58,880 58,740 63,000 59,620 59,400 60,580 59,460 60,340 60,240 60,020 59,180 59,980 Xr = 60 , 182 Position (270°) 61,970 59,200 61,070 60,000 59,340 59,220 60,590 58,880 60,520 59,420 Xr = 60 , 021 The following calculation uses Formula (5): b od = 60 , 182 B.3.3.2 N⋅m − 59 , 262 N⋅m = , 920 N⋅m Relative standard measurement uncertainty, wod Using the formula taken from Table 3, the values are presented in Table B.6 Table B.6 Xa N·m 60 180 300 b od N·m 0,920 0,920 0,920 Xr N·m 59,134 178,532 301,034 wod % 0,449 0,149 0,088 B.3 Variation of interface between the tool and the calibration system (see 6.2.3.3) B.3.4.1 Variation due to geometric effects of the interface between the output drive of the torque tool and the calibration system, b int Table B.7 gives the values observed when rotating the interface adapter according to 6.2.3.3 28 © ISO 2017 – All rights reserved ISO 6789-2:2 017(E) Table B.7 Reference value Target value Xr Tmin N∙m N∙m Position (0°) Position (90°) Position (180°) Position (270°) X r = 59 , 098 X r = 59 , 098 X r = 58 , 990 X r = 58 , 990 61,010 58,710 58,700 58,650 59,060 58,840 58,990 58,600 59,300 59,120 60 61,010 58,710 58,700 58,650 59,060 58,840 58,990 58,600 59,300 59,120 58,660 59,010 58,650 59,080 59,090 58,530 59,080 58,960 59,750 59,090 58,660 59,010 58,650 59,080 59,090 58,530 59,080 58,960 59,750 59,090 The following calculation uses Formula (6): b int = 59 , 098 N ⋅ m − 58 , 990 N ⋅ m = , 108 N ⋅ m B.3.4.2 Relative standard measurement uncertainty, wint Using the formula taken from Table 3, the values are presented in Table B.8 Table B.8 Xa N·m 60 180 300 b int N·m 0,108 0,108 0,108 Xr N·m 59,134 178,532 301,034 Wint % 0,053 0,017 0,010 B.3.5 Variation of the torque loading point (see 6.2.4) B.3.5.1 Variation due to the length variation of the torque loading point, b l Table B.9 gives the values taken according to 6.2.4 © ISO 2017 – All rights reserved 29 ISO 6789-2 :2017(E) Table B.9 Reference value Target value Xr Tmin N∙m N∙m P o s i t i o n ( − m Position (+10 mm) m ) 61,010 58,710 58,700 58,650 59,060 58,840 58,990 58,600 59,300 59,120 60 58,660 59,010 58,650 59,080 59,090 58,530 59,080 58,960 59,750 59,090 X r = 59 , 098 X r = 58 , 990 The following calculation uses Formula (7): b = 59 ,098 l B.3.5.2 N ⋅ m − ,9 90 N ⋅ m = ,1 08 N ⋅m Relative standard measurement uncertainty, wl Using the formula taken from Table 3, the values are presented in Table B.10 Table B.10 Xa N·m 60 180 300 bl N·m 0,108 0,108 0,108 Xr N·m 59,134 178,532 301,034 wl % 0,053 0,017 0,010 B.3 Repeatability of the torque tool (see 6.3) B.3.6.1 Variation due to the repeatability, b re Table B.11 gives the values observed and the variation calculated according to Formula (8) 30 © ISO 2017 – All rights reserved ISO 6789-2:2 017(E) Table B.11 Target values Xa Reference value Deviation Variation due to the repeatability Xr ( Xr − Xr ) b re N∙m N∙m N∙m Xa = N ∙ m at 20 % Tmax 59,210 59,170 59,070 59,020 59,200 X r = 59 , 134 Xa = N ∙ m at 60 % Tmax 179,050 178,590 178,800 177,830 178,390 X r = 178 , 532 Xa = 0 N ∙ m at 100 % Tmax 301,640 301,500 301,130 300,860 300,040 X r = 301 , 034 B.3.6.2 0,076 0,036 −0,064 − ,1 14 0,084 − ,70 0,463 0,066 — 0,518 0,058 0,268 − ,142 — 0,606 0,466 0,096 − ,174 0,635 − ,9 — Relative standard measurement uncertainty, wre Using the formula taken from Table 3, the values are presented in Table B.12 Table B.12 Xa b re Xr N∙m N∙m N∙m 60 180 300 0,084 0,463 0,635 59,134 178,532 301,034 wre % 0,064 0,116 0,094 B.3.7 Relative measurement uncertainty interval of the calibration device, The value of W md f Formula C.11 can be used to assist if required ′ s b e en ta ken W′md rom the c u rrent c a l ibration cer ti fic ate o f the c a l ibration device = ±1,00 % Wmd = ±0,30 % Maximum relative value of the measurement error, bep = 0,70 % Relative me a s u rement u ncer tai nty i nter va l, W′md Relative exp a nde d me a s urement u ncer tai nty, © ISO 2017 – All rights reserved 31 ISO 6789-2 :2017(E) The value of W md is less than 1/4 of the expected value of W according to 4.3 ′ ′ a nd th i s fu l fi l s the re qu i rements B.4 Calculation B.4.1 Determination of the relative standard measurement uncertainty, w The data presented in Table B.13 are rounded to three decimal places and combined using Formula (11) to produce the results for w rounded to three decimal places and presented in Table B.14 Table B.13 Xa Wmd N·m 60 180 300 B.4.2 % 0,3 0,3 0,3 wr wint % 0,053 0,017 0,010 wrep % 0,488 0,162 0,096 % 0,836 0,277 0,164 wod wl % 0,053 0,017 0,010 0,449 0,149 0,088 wre % 0,064 0,116 0,094 Determination of the relative expanded measurement uncertainty, W The results for W using Formula (12) with k = are rounded to three decimal places and presented in Table B.14 Table B.14 Xa w 60 180 300 B.4.3 W % 1,082 0,402 0,275 N∙m % 2,164 0,804 0,549 Determination of the relative measurement uncertainty interval, W′ The results using Formula (13) are presented in Table B.15 Table B.15 Calibration value Xa N∙m 60 180 300 Mean value of the measurement error | as | % 1,465 0,823 0,343 Relative expanded measurement uncertainty Maximum value of the calibration device measurement error Relative measurement uncertainty interval b ep W′ W % 2,164 0,804 0,549 | | % 0,70 0,70 0,70 % 4,329 2,327 1,592 B.5 Conclusion of this calculation example In this example, the expected values of as and W — Maximum as: 1,660 % is smaller than the expected measurement error, as: ±3 % ′ a re ach ieve d: 32 © ISO 2017 – All rights reserved ISO 6789-2 : 01 7(E) — Maximum W ′: 4, % i s s ma l ler tha n the e xp e c te d relative u ncer ta i nty i nter va l , © ISO 2017 – All rights reserved W ′: ± % 33 ISO 6789-2:2017(E) Annex C (normative) Minimum requirements for the calibration of the torque measurement device and the estimation of its measurement uncertainty C.1 General Where the torque measurement device calibrated by a laboratory meeting the requirements o f ISO/IEC 17025, the maximum relative measurement uncertainty interval ′md may be stated on the calibration certificate o f that calibration device calibrate W Where this information is not available, Annex C provides the minimum requirements for the calibration o f the torque measurement device and the estimation o f its measurement uncertainty interval, W′md C.2 Symbols For the application o f this annex, the symbols, units and terms stated in Table are applicable C.3 General guidelines for the reference measurement standard Step by step or progressive calibration is achieved by the incremental loading o f the measurement device to be calibrated An example of a progressive loading method is using a length beam and a series o f masses that generate a force under gravity In continuous calibration, the torque measurement device is subjected to a continuously changing load An example o f a continuous loading method is using a length beam and hydraulic cylinders delivering a measurably increasing force Trans fer torque wrenches can also be used to measure the torque provided by the measurement device being calibrated The torque can be increased in a progressive or continuous manner The reference measurement standard should be designed and assembled such that both clockwise and anti-clockwise torque can be applied without the significant influence o f non-torsional forces, such as bending moments The torque measurement axis can be either horizontal or vertical The pre ferred orientation reflects the orientation of the measurement device when in use Where a re ference measurement standard is achieved by means o f a trans fer torque wrench, it shall be possible to vary the lever arm length over the range o f the lever arm lengths o f commercially available torque tools having the measurement range to be calibrated C.4 Calibration of the measurement device C.4.1 General requirements W The measurement uncertainty interval, ′ref, of the reference measurement standard shall not exceed 2/5 o f the claimed measurement uncertainty interval, ′md , of the torque measurement device to be calibrated at each calibration value 34 W © ISO 2017 – All rights reserved ISO 6789-2:2017(E) C.4.2 Combined relative uncertainty of calibration of the measurement device, wmd,c Where the torque me as u rement device s i s ts o f a tra n s ducer a nd a n ele c tric a l i nd ic ator or d i s play with s ep arate acc u racie s , the combi ne d u ncer tai nty c an b e de term i ne d b y combi n i ng the s ep arate uncertainties using the square root of the sum of the squares T h i s va lue i s defi ne d a s the combi ne d relative me as u rement device u ncer tai nty, w md,c wmd,c ; s e e Formu la (C 1) : 2 = w md,t + w md,d (C.1) C.4.3 Calibration device indicators Where an electrical indicator is replaced with another, both indicators shall have a valid calibration cer ti fic ate trace ab le to nationa l s tandard s T he repl acement i nd ic ator s l l have b e en c a l ibrate d over at le as t the s ame nge o f i nd ication a s the origi na l i nd ic ator Where the u ncer ta i nty o f c a l ibration o f the replacement i nd ic ator d i ffers from measurement device shall be recalculated the origi na l, the s tandard me as u rement uncer ta i nty o f the C.4.4 Resolution of the measurement device, r C.4.4.1 Analogue scale The thickness of the graduation marks on the scale should be uniform, and the width of the pointer r, of the indicator shall f f f scale marks Recommended ratios are 1/2, 1/5 or 1/10 Centre-to-centre distances equal to or larger than 1,25 mm are required to estimate a tenth of the scale division shou ld b e approxi mately e qua l to the width o f a graduation ma rk: the re s olution, b e ob tai ne d rom the ratio o the width o the p oi nter to the centre -to - centre d i s tance b e twe en adj acent C.4.4.2 Digital scale The value of r f more than one increment when the device is at the lowest calibrated torque value, or in cases where the s l l b e one i nc rement o the la s t ac tive d igit, provide d the d i s play e s no t va r y by re ad i ngs fluc tuate, one i nc rement o f the l as t ac tive d igit plu s one h a l f o f the fluc tuation range C.4.4.3 Resolution units The resolution r shall be converted into and indicated in torque units C.4.5 Lowest allowable value for the minimum limit of the measurement range, TA The lowest allowable value for TA shall be determined using Formula (C.2): T ≥ Wr′ A (C.2) 100 md The lowest allowable value for TA shall not be less than % of the maximum torque value of the measurement range EXAMPLE TA ≥ For an expected W′md of 0, % a nd a re s o lutio n of 0, N∙m, the re qu i rement wi l l a l low N·m Where the measurement device has a resolution that changes through the range, the value of r shall be the value at TA © ISO 2017 – All rights reserved 35 ISO 6789-2 :2017(E) C.4.6 C.4.6.1 Preparation of the calibration Measurement device The measurement device shall be adjusted according to the manu facturer’s instructions Prior to the calibration, it is recommended that the measurement device is subject to a check to ensure that it functions correctly and will allow a sa fe and valid calibration All adjustments and, where appropriate, corresponding setting values should be recorded before and after the calibration C.4.6.2 Temperature stabilization Prior to calibrating the torque measurement device, it shall be stored with the supply power applied in the calibration environment for su fficient time for its temperature to stabilize C.4.6.3 Mounting of the transducer Failure to apply the calibration torque in the orientation stated by the manu facturer, or specified by the customer, may lead to erroneous measurements The orientation shall be documented in the certificate C.4.7 C.4.7.1 Calibration procedure Preloading The torque measurement device shall be preloaded three times in the direction to be calibrated, applying the maximum torque value, TE , of the measurement range of the measurement device, and additionally once a fter each change o f the mounting position The duration o f the application o f preload should be not less than 30 s The indicator reading shall be taken before each preload and after each preload has been removed for not less than 30 s, the indicator reading shall again be recorded NOTE The stability o f the zero signal can provide an indication o f the per formance o f the device during its calibration C.4.7.2 Mounting position For torque measurement devices utilizing a square drive, four mounting positions are preferred although dependent on the performance of the measurement device and the customer requirements, two mounting positions may be su fficient Torque measurement devices without square drive shall be calibrated in three different mounting measurement axis If the torque measurement device cannot be rotated, it shall be dismounted and remounted from the positions with the transducer or its mechanical coupling part rotated each time through 120° about the re ference measurement standard to determine reproducibility Two incremental calibration series are required at the same mounting position, normally at the start o f calibration, for determination o f repeatability Position 0° Position 90° Position 180° Position 270° Figure C.1 — Examples of preloading and sequences for torque measurement devices with s 36 q u a r e d r i v e ( m i n i m u m o f f i v e s t e p s ) © ISO 2017 – All rights reserved ISO 6789-2:2 017(E) Position 0° Position 120° Position 240° Figure C.2 — Examples of preloading and sequences for torque measurement devices with hexagon drive (minimum of four steps) C.4.7.3 Range of calibration The recommended number o f calibration steps shall be a minimum o f five approximately equally spaced from 20 % to 100 % of TE For the calculation o f a fitting curve, a minimum o f five steps shall be taken When calibration points below 20 % of TE are required, additional steps may be specified provided that they comply with C.4.5 The time interval between two successive calibration steps shall, if possible, be similar Recording the measured value shall take place only a fter the indication has stabilized and no sooner than 30 s a fter the application o f the calibration step A fter the final calibration step o f each series, the measurement device reading in unloaded condition, Iz , shall be recorded C.4.7.4 Loading conditions Calibration shall be carried out at a temperature stable to ±1 K This temperature shall be in the range between 18 °C and 28 °C (pre ferably between 20 °C and 22 °C) and recorded The humidity shall not exceed 65 % and shall be recorded C.5 C.5.1 Measurement error Indicated value, X The indicated value is defined as the di fference between an indication in loaded condition and an indication in unloaded condition X = I – I0 (C.3) The indication at the beginning o f each measurement series shall be zeroed or taken into account by computation during the evaluation following the measurement NOTE Recording of the indication in unloaded condition provides additional information about the measurement device © ISO 2017 – All rights reserved 37 ISO 6789-2:2017(E) C.5.2 Determination of mean value, X r The mean value, X r , for each torque level shall be calculated according to Formula (C.4) as the mean value of the measurement results obtained in the increasing series in changed mounting positions: Xr = where n n∑ j =1 (I j − Ij,0 ) (C.4) j i s the i nde x o f s ele c te d s erie s; n is the number of increasing series in different mounting positions T he va lue s me a s u re d i n the s e cond s er ie s o f the ° p o s ition a re no t i nclude d i n the c a lc u l ation o f NO TE Xr C.5.3 Recorded measurement error, b e The measurement error is calculated according to Formula (C.5) for each torque level from the mean value of all increasing series b =X −X (C.5) e r ref C.6 Sources of uncertainty C.6.1 Evaluation of Type A uncertainties due to the torque measurement device — Determination of repeatability, b re T he rep e atabi l ity i n u ncha nge d mou nti ng p o s ition sh a l l b e c a lc u l ate d Formula (C.6): b re = X1   where X1 −   for e ach torque level accord i ng to (C.6) X and X2 are the values measured in unchanged position C.6.2 Evaluation of Type B uncertainties due to the torque measurement device C.6.2.1 Determination of reproducibility, b rep T he repro ducibi l ity i n change d mounti ng p o s ition sha l l b e c a lc u late d the following formula: b rep = Xmax Xmin for e ach torque level accord i ng to (C.7) − NO TE T he va lue s me a s u re d i n the s e cond s er ie s o f the ° p o s ition a re no t i nclude d i n the c a lc u l ation o f b rep C.6.2.2 Measurement hysteresis error of the zero signal, bz To eva luate the u ncer tai nty cre ate d b y z ero d ri ft, the i nd ic ation i n u n lo ade d cond ition lo ad i ng s erie s defi ne d i n 38 C.4.7.3 shall be used fol lowi ng e ach © ISO 2017 – All rights reserved ISO 6789-2:2 017(E) The deviation of the zero signal, bz , shall be calculated using Formula (C.8): b z = max I where j = 1, 2, …, n C.6.3 z,j (C.8) − I0 is the number o f loading cycles Thermal sensitivity During calibration and use, different temperatures, thermal drifts and temperature gradients can shall include these factors influence the measurement results Where such influences are present, the calculation o f uncertainty C.7 Determination of the calibration result C.7.1 Determination of the relative standard measurement uncertainty, wmd The relative standard measurement uncertainty, wmd , assigned to the measurement calibration point is given for uncorrelated input quantities by Formula (C.9): w md W =  ref   device at each  2  w r2 + w z2 + w re + w rep   (C.9) The formulae for calculating elements o f the relative standard uncertainty are shown in Table C.1 The expanded standard measurement uncertainty, reference measurement standard Wref, can be obtained from the certificate o f Because readings are taken twice (at the scale’s zero point or minimum, respectively, and at the calibration value), the measurement uncertainty o f the resolution, r, appears in the result twice These two random fractions are added up geometrically Table C.1 — Distribution functions for calculating the relative standard measurement uncertainties for characteristic values calculated from the variation ranges determined experimentally Clause reference C.4.4 Characteristic value Distribution function B Uncertainty due to the resolution o f Type Rectangular the measurement device distribution Type B due to the zero dri ft o f Rectangular C.6.2.2 Uncertainty the measurement device distribution Type B Relative standard measurement uncertainty, w wr = wz = due to the reproducibility Rectangular C.6.2.1 Uncertainty of the measurement device distribution w rep = A Uncertainty due to the repeatability Type Rectangular w re = C.6.1 of the measurement device © ISO 2017 – All rights reserved distribution in % , r × ,5 bz × ,5 b rep × ,5 Xr × × ,5 b re 100 × 100 Xr × × 100 Xr 100 Xr 39 ISO 6789-2 :2017(E) Determination of the relative expanded measurement uncertainty, Wmd C.7.2 The relative expanded measurement uncertainty, Wmd , of the calibration result for the measurement device is calculated from the standard measurement uncertainty multiplied by the coverage factor, k The default value of k = A check shall be made in order to ensure a confidence interval o f approximately 95 % (C.10) Wmd = k × w md NOTE and G Further information on the value of k can be determined from ISO/IEC Guide 98-3:2008, Annexes C C.7.3 Determination of the relative measurement uncertainty interval, The relative measurement uncertainty interval, W′md, o f W′md a calibration including all systematic and random components shall be calculated using Formulae (C.11) and (C.12): (C.11) ′ = max b ep + b ref,ep + Wmd Wmd where b ref,ep = max( b ref,e ) X ref in % (C.12) The measurement error, bref,e, can be obtained from the certificate of the reference measurement standard C C a l i b r a t i o n c e r t i f i c a t e Calibration certificates in accordance with Annex C shall comply with ISO/IEC 17025 and contain at least the following additional information: a) identification o f certificate stating that it is a certificate in accordance with Annex C ; b) identity o f all elements o f the calibration device and the adaptors; c) in formation on the lever arm lengths, i f using a trans fer standard; d) position o f the measurement axis during the calibration (horizontal and/or vertical); e) calibration result according to Annex C, including the evaluated mean values together with the measurement uncertainty values according to C.5.4 The calibration certificate may include in addition: — a table o f the measurement values and o f the calculated characteristic values; — graphic representation of the characteristic curve 40 © ISO 2017 – All rights reserved ISO 6789-2:2017(E) Bibliography [1] ISO 1703:2005, Assembly tools for screws and nuts — Designation and nomenclature [2] ISO/TS 16949, Quality management systems — Particular requirements for the application of ISO 9001:2008 for automotive production and relevant service part organizations [3] ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) [4] ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and associated terms (VIM) [5] BS 7882, [6] DAkkS-DKD-R [7] DIN 51309, Werkstoffprüfmaschinen — Kalibrierung von Drehmomentmessgeräten für statische Drehmomente (Materials testing machines — Calibration of static torque measuring devices) [8] EA-4/01, Requirements concerning certificates issued by accredited calibration laboratories [9] EA-4/02, Expression o f the uncertainty o f measurement in calibration [10] EA-10/14, EA Guidelines on the Calibration o f Static Torque Measuring Devices [11] VDI/VDE 2646, Drehmomentmessgeräte — Mindestanforderungen an Kalibrierungen M e t h o d   f o r   c a 3-8, l i b r a t i o n   a d   c l a Statische Drehmomentschraubwerkzeuge © ISO 2017 – All rights reserved n s s f i i c a t i o n   o f   t o Kalibrierung r q u e   m e von a s u r i n g   d e v i c e s Kalibriereinrichtungen ür f 41 ISO 6789-2 : 01 7(E) ICS  25.140.30 Price based on 41 pages © ISO 2017 – All rights reserved