1、BS 7882:2008Method for calibration and classification of torque measuring devicesICS 17.100NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDLicensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSIPublishing and copyright
2、 informationThe BSI copyright notice displayed in this document indicates when the document was last issued. BSI 2008ISBN 978 0 580 55351 6The following BSI references relate to the work on this standard:Committee reference ISE/NFE/4Draft for comment 07/30133498 DCPublication historyFirst published
3、May 1997Second edition, January 2008Amendments issued since publicationAmd. no. Date Text affectedBS 7882:2008Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSI BSI 2008 iBS 7882:2008ContentsForeword ii1 Scope 12 Terms, definitions, abbreviations and
4、symbols 13 Preparation for calibration 34 Calibration procedure 75 Calculation of results 86 Classification of torque measuring devices 117 Calibration certificate 13AnnexesAnnex A (informative) Orientation diagrams 14Annex B (informative) Method example of determining uncertainty of the calibration
5、 results of the torque measuring device 16Bibliography 25List of figuresFigure A.1 Example of preloading and calibration sequences for a torque measuring device with round shaft drives, six increasing and decreasing torques, classes 0.05 to 5.0 14Figure A.2 Example of preloading and calibration sequ
6、ences for a torque measuring device with round shaft drives, six increasing torques only, classes 0.05 to 5.0 14Figure A.3 Example of preloading and calibration sequences for a torque measuring device with square drives, six increasing and decreasing torques, classes 0.05 to 5.0 14Figure A.4 Example
7、 of preloading and calibration sequences for a torque measuring device with square drives, six increasing torques only, classes 0.05 to 5.0 15Figure A.5 Example of preloading and calibration sequences for a torque measuring device, six increasing and decreasing torques, classes 0.2 to 5.0. 15Figure
8、A.6 Example of preloading and calibration sequences for a torque measuring device, six increasing torques only, classes 0.2 to 5.0 15Figure B.1 Worked example in torque units: 100 Nm torque measuring device clockwise torque, increasing series only 19Figure B.2 Uncertainties calculated in accordance
9、with B.3 20Figure B.3 Worked example in mV/V: 2 kNm torque measuring device clockwise torque, increasing and decreasing series 22Figure B.4 Uncertainties calculated in accordance with B.4 24List of tablesTable 1 Uncertainty of calibration torques 3Table 2 Criteria for classification of torque measur
10、ing devices 12Summary of pagesThis document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 25 and a back cover.Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSIBS 7882:2008ii BSI 2008ForewordThis British Standard is publis
11、hed by BSI and came into effect on 31 January 2008. It was prepared by Technical Committee ISE/NFE/4, Torque measurement and testing. A list of organizations represented on this committee can be obtained on request to its secretary.SupersessionBS 7882:2008 supersedes BS 7882:1997, which is withdrawn
12、.Presentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.Commentary, explanation and general informative material is presented in smaller italic type, and does n
13、ot constitute a normative element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Licensed C
14、opy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSI BSI 2008 1BS 7882:20081 ScopeThis British Standard specifies requirements for the calibration and classification of torque measuring devices, including those used for the calibration of hand torque tools to BS
15、EN ISO 6789. It describes the method of calibration, calculation of calibration results and the classification of the torque measuring device in a static mode. The information to be given on the certificate of calibration is also listed.2 Terms, definitions, abbreviations and symbols For the purpose
16、s of this British Standard, the following terms, definitions, abbreviations and symbols apply.NOTE Where applicable, this British Standard has been prepared using PD 6461-1.2.1 calibration torquetorque with traceability derived from national standards of mass, length and time, and of specified uncer
17、tainty of measurement, which can be applied to the torque measuring device2.2 deflection dalgebraic difference between the indicator reading prior to the application of a torque and the indicator reading for each applied torque in a given measurement seriesNOTE The deflection may be derived from eit
18、her digital data output or visual data output.2.3 data acquisition systemelectronic module that has the ability to transfer, store, amplify and filter signals from a torque measuring device NOTE Where analogue signals are acquired by the torque measuring device, and these are converted into a digita
19、l data stream using an analogue to digital converter, the stream of data may be digitally filtered, re-sampled and stored, or logged ready for analysis.2.4 loading directiondirection of applied torque, either clockwise or anti-clockwise about the axis of rotation, when viewed from the end of the tor
20、que measuring device to which the calibration torque is applied2.5 lower limit of calibration Tminlower value of torque at which a torque measuring device of a given class can be calibrated2.6 reference standardequipment used to generate or to measure the reference torque applied to the torque measu
21、ring device that is being calibratedNOTE Torques may be generated by a power source monitored by the reference standard. Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSIBS 7882:20082 BSI 20082.7 relative error of indication Eimean deflection for a g
22、iven value of increasing torque minus the corresponding value of applied torque NOTE 1 For the purposes of this standard, relative error of indication is expressed as a percentage of applied torque.NOTE 2 Relative error of indication is only used where the deflection is in units of torque.2.8 relati
23、ve error of interpolation Eitdifference between the value of the mean deflection for a given value of increasing torque and the corresponding calculated value of deflection for the given torque, obtained from a mathematically fitted curve NOTE For the purposes of this standard, relative error of int
24、erpolation is expressed as a percentage of the computed deflection for the given increasing torque.2.9 relative repeatability R1closeness of the agreement between the results of two successive measurements from the same applied torque, carried out under the same conditions of measurement2.10 relativ
25、e reproducibility R2closeness of agreement between the results of successive measurements from the same applied torque, carried out under changed conditions of measurement2.11 relative residual deflection R0maximum residual deflection obtained from all the series of torquesNOTE For the purposes of t
26、his standard, relative residual deflection is expressed as a percentage of the mean deflection for the maximum torque applied.2.12 relative reversibility R3difference between the deflection obtained from the last given torque series applied in an increasing mode and the deflection obtained from the
27、same given torque applied in a decreasing mode NOTE For the purposes of this standard, relative reversibility is expressed as a percentage of the deflection of the last series for the given torque, applied in an increasing mode.2.13 residual deflection d0algebraic difference between the indicator re
28、adings before and after the application of a single series of torques2.14 resolution rsmallest discernable measurement interval on the torque measuring device indicatorLicensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSI BSI 2008 3BS 7882:20082.15 torqu
29、eproduct of tangential force and length applied about a known centre of rotation2.16 torque measuring devicesystem comprising an electrical, mechanical, hydraulic or optical torque measuring device, with associated instrumentation, including the automated logging of data when part of the deviceNOTE
30、The instrumentation can be an electronic instrument, a mechanical device, i.e. a scale and pointer system, or a Bourdon tube instrument.3 Preparation for calibration3.1 Reference standard3.1.1 Uncertainty of calibration torquesValues for the maximum permissible uncertainty of the calibration torques
31、 applied for the determination of different classifications of the torque measuring device shall not exceed the values given in Table 1. Where a reference standard is used to determine a calibration torque, it shall conform to Table 1.3.1.2 Traceability of measurementsAll definitive measurements, su
32、ch as mass, length, time and temperature, shall be traceable to national standards; evidence of this shall be provided by a certificate of calibration.3.2 Condition and identification of a torque measuring device3.2.1 Calibration shall not be commenced unless the torque measuring device is considere
33、d to be in good working order and is identified with a serial number. The maximum working torque shall first have been established.NOTE Good working order includes the drive components being of a sufficiently good fit to exert a minimum bias on the system.Table 1 Uncertainty of calibration torquesCl
34、ass of torque measuring device to be calibratedMaximum permissible uncertainty of calibration torque appliedA)%0.05 0.010.1 0.020.2 0.040.5 0.101.0 0.202.0 0.405.0 1.00A)Using a coverage factor of k = 2 to give a confidence level of approximately 95%.Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STAND
35、ARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSIBS 7882:20084 BSI 20083.2.2 All parts of the torque measuring device shall be identified in accordance with 3.2.1, including the following, where applicable:a) signal cables;b) switch boxes; c) interfaces; d) data acquisition systems; e) computers; a
36、ndf) software (where information is available).3.2.3 Where an electrical indicator used with a torque measuring device is replaced with another, the following requirements shall be met to ensure that the calibration is not invalidated.a) The original indicator shall have a valid calibration certific
37、ate, traceable to national standards, that gives the results of a calibration made in terms of the units to be measured. The indicator shall have been calibrated over a range equal to or greater than the range over which it is used with the torque measuring device. b) The replacement indicator shall
38、 have a resolution equal to or better than the indicator it is replacing and shall have a valid calibration certificate, traceable to national standards, that gives the results of a calibration made in terms of the units to be measured. The indicator shall have been calibrated over a range equal to
39、or greater than the range over which it is used with the torque measuring device.c) The date of calibration on the certificate for the original indicator shall not precede that of the certificate for the replacement indicator by more than 12 months.d) The certificates for the two indicators show tha
40、t the readings of the torque measuring device, as measured by the two indicators, agree with the values given below, over the range of the classification of the torque measuring device: 0.025% of indicated reading for a class 0.05 device; 0.050% of indicated reading for a class 0.1 device; 0.10% of
41、indicated reading for a class 0.2 device; 0.25% of indicated reading for a class 0.5 device; 0.50% of indicated reading for a class 1.0 device; 1.00% of indicated reading for a class 2.0 device; 2.50% of indicated reading for a class 5.0 device.e) If it is necessary to replace cables, the replacemen
42、t cables shall be of the same specification as the originals to ensure that the calibration remains valid.Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSI BSI 2008 5BS 7882:20083.3 Resolution of the indicator NOTE An indicator can be a direct readin
43、g display or the output of a data acquisition system.3.3.1 Analogue scaleWhen the output of the torque measuring device is measured by an indicator with an analogue scale, i.e. a dial gauge or Bourdon tube instrument, the resolution r shall be determined from the ratios between the width of the poin
44、ter and the centre-to-centre distance between two adjacent scale graduation marks (scale interval). NOTE The ratios should be 1/2, 1/5 or 1/10. A spacing of at least 1.25 mm shall be used for the estimation of a tenth of the division on the scale. When using an optical recognition system, i.e. video
45、, the video frame rate shall be at least 10 times the display update being recorded.A vernier scale of dimensions appropriate to the analogue scale may be used to allow direct fractional reading of the instrument scale division.3.3.2 Digital scaleThe resolution shall be considered to be one incremen
46、t of the last active number of the numerical indicator.3.3.3 Variation of readingsIf the readings fluctuate by more than the value previously calculated for the resolution (with no torque applied to the instrument), the resolution shall be deemed to be equal to half the range of fluctuation.3.3.4 Un
47、itsThe resolution r shall be converted to units of torque.3.4 Lower limit of calibration TminTo ensure that the classification is consistent with the resolution of the torque indicator, a lower limit of calibration shall be determined. The calibration shall not be performed below this lower limit, g
48、iven by the equation:Tmin= arwhere:r is the resolution determined in accordance with 3.3a has the following values: 4 000 for a class 0.05 torque measuring device; 2 000 for a class 0.1 torque measuring device; 1 000 for a class 0.2 torque measuring device; 400 for a class 0.5 torque measuring devic
49、e; 200 for a class 1.0 torque measuring device; 100 for a class 2.0 torque measuring device; 40 for a class 5.0 torque measuring device.Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 26/02/2008 02:43, Uncontrolled Copy, (c) BSIBS 7882:20086 BSI 20083.5 Number of calibration orientations (see Annex A)For classes 0.05 and 0.1, the torque measuring device shall be calibrated in either three different mounting positions, each rotated 120 about the measurement axis, or in four differe
