BS 7882:2008
$142.49
Method for calibration and classification of torque measuring devices
| Published By | Publication Date | Number of Pages |
| BSI | 2008 | 30 |
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 3 | Contents 1 Scope 1 2 Terms, definitions, abbreviations and symbols 1 3 Preparation for calibration 3 4 Calibration procedure 7 5 Calculation of results 8 6 Classification of torque measuring devices 11 7 Calibration certificate 13 Annexes Annex A (informative) Orientation diagrams 14 Annex B (informative) Method example of determining uncertainty of the calibration results of the torque measuring device 16 Bibliography 25 List of figures Figure 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 14 Figure A.2 – Example of preloading and calibration sequences for a torque measuring device with round shaft drives, six increasing torques only, classes 0.05 to 5.0 14 Figure A.3 – Example of preloading and calibration sequences for a torque measuring with square drives, six increasing and decreasing torques, classes 0.05 to 5.0 14 Figure A.4 – Example of preloading and calibration sequences for a torque measuring device with square drives, six increasing torques only, classes 0.05 to 5.0 15 Figure A.5 – Example of preloading and calibration sequences for a torque measuring device, six increasing and decreasing torques, classes 0.2 to 5.0. 15 Figure A.6 – Example of preloading and calibration sequences for a torque measuring device, six increasing torques only, classes 0.2 to 5.0 15 Figure B.1 – Worked example in torque units: 100 N·m torque measuring device clockwise torque, increasing series only 19 Figure B.2 – Uncertainties calculated in accordance with B.3 20 Figure B.3 – Worked example in mV/V: 2 kN·m torque measuring device clockwise torque, increasing and decreasing series 22 Figure B.4 – Uncertainties calculated in accordance with B.4 24 List of tables Table 1 – Uncertainty of calibration torques 3 Table 2 – Criteria for classification of torque measuring devices 12 |
| 4 | Foreword |
| 5 | 1 Scope 2 Terms, definitions, abbreviations and symbols 2.1 calibration torque 2.2 deflection 2.3 data acquisition system 2.4 loading direction 2.5 lower limit of calibration 2.6 reference standard |
| 6 | 2.7 relative error of indication 2.8 relative error of interpolation 2.9 relative repeatability 2.10 relative reproducibility 2.11 relative residual deflection 2.12 relative reversibility 2.13 residual deflection 2.14 resolution |
| 7 | 2.15 torque 2.16 torque measuring device 3 Preparation for calibration 3.1 Reference standard 3.1.1 Uncertainty of calibration torques Table 1 Uncertainty of calibration torques 3.1.2 Traceability of measurements 3.2 Condition and identification of a torque measuring device |
| 8 | a) signal cables; b) switch boxes; c) interfaces; d) data acquisition systems; e) computers; and f) software (where information is available). a) The original indicator shall have a valid calibration certificate, traceable to national standards, that gives the results of… b) The replacement indicator shall have a resolution equal to or better than the indicator it is replacing and shall have a vali… 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 that 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: e) If it is necessary to replace cables, the replacement cables shall be of the same specification as the originals to ensure that the calibration remains valid. |
| 9 | 3.3 Resolution of the indicator 3.3.1 Analogue scale 3.3.2 Digital scale 3.3.3 Variation of readings 3.3.4 Units 3.4 Lower limit of calibration Tmin |
| 10 | 3.5 Number of calibration orientations (see Annex A) 3.6 Preliminary procedure 3.6.1 Alignment 3.6.2 Temperature considerations 3.6.3 Indicator set-up |
| 11 | 3.6.4 Preloading procedure 4 Calibration procedure 4.1 Selection of calibration torques 4.2 Application of calibration torques a) clockwise or anti-clockwise direction (see 4.2.2); or b) b) in both clockwise and anti-clockwise directions (see 4.2.8). |
| 12 | 5 Calculation of results 5.1 Determination of deflection (d) 5.2 Determination of relative repeatability (R1) |
| 13 | 5.3 Determination of relative reproducibility (R2) 5.4 Determination of relative error of interpolation (Eit) |
| 14 | 5.5 Determination of relative residual deflection (R0) 5.6 Determination of relative reversibility (R3) 5.7 Determination of relative error of indication (Ei) |
| 15 | 6 Classification of torque measuring devices 6.1 Procedures for classification 6.1.1 General a) repeatability; b) reproducibility; c) residual deflection; and d) error of indication. a) repeatability, b) reproducibility, c) residual deflection; and d) error of interpolation. |
| 16 | 6.1.2 Determination of a classification and its range Table 2 Criteria for classification of torque measuring devices |
| 17 | 7 Calibration certificate 7.1 General a) The date of the issue of this certificate, which shall also be identified by a unique reference. b) The date of calibration. c) The serial numbers of the torque measuring device and, where appropriate, any mechanical fittings and electrical cables. d) A brief description of the calibration method and the type of calibration equipment used, including the uncertainty of measurement of the applied calibration torque. e) A reference to this standard as a basis of test, i.e. BS 7882:2008. f) The range and loading mode of torques over which the torque measuring device conforms to Clause 3 to Clause 6, for a given classification. g) Where the unit of deflection is expressed in units of torque it shall be stated that the device conforms to the parameters of… h) Where the unit of deflection is expressed in units of other than those of torque it shall be stated that the device conforms … i) The uncertainty of measurement for the calibration values given (see Annex B). j) The average temperature and its range of variation or the maximum and minimum temperature recorded of the torque measuring device during the calibration. k) A table of the applied torques and corresponding deflections. 7.2 Frequency of calibration |
| 18 | Annex A (informative) Orientation diagrams |
| 20 | Annex B (informative) Method example of determining uncertainty of the calibration results of the torque measuring device B.1 Uncertainty of the calibration results B.1.1 General B.1.2 Calculation of calibration torque uncertainty, u1 |
| 21 | B.1.3 Calculation of reproducibility uncertainty, u2 B.1.4 Calculation of repeatability uncertainty, u3 B.1.5 Calculation of resolution uncertainty, u4 B.1.6 Calculation of residual deflection uncertainty, u5 B.1.7 Calculation of temperature uncertainty, u6 |
| 22 | B.1.8 Calculation of error of interpolation uncertainty, u7 B.1.9 Calculation of reversibility uncertainty, u8 B.1.10 Calculation of combined standard uncertainty, uc B.1.11 Calculation of expanded uncertainty, U B.2 Overall accuracy of the device, Oa B.3 Worked examples of calculation of uncertainty of the calibration results of the torque measuring device calibrated in torque units (increasing torques only) |
| 23 | Figure B.1 Worked example in torque units: 100 N·m torque measuring device clockwise torque, increasing series only |
| 24 | Figure B.2 Uncertainties calculated in accordance with B.3 |
| 25 | B.4 Worked examples of calculation of uncertainty of the calibration results of the torque measuring device calibrated in units other than torque (increasing and decreasing torques) |
| 26 | Figure B.3 Worked example in mV/V: 2 kN·m torque measuring device clockwise torque, increasing and decreasing series |
| 27 | Figure B.3 Worked example in mV/V: 2 kN·m torque measuring device clockwise torque, increasing and decreasing series (continued) |
| 28 | Figure B.4 Uncertainties calculated in accordance with B.4 |
| 29 | Bibliography |
