1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsWB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1Torque measuring devices Calibration and classification using continual torque application MethodBS 7996:2009BS 7
2、996:2009 BRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when the document was last issued. BSI 2009ISBN 978 0 580 53116 3ICS 17.100The following BSI references relate to the work on this standard: Committee reference ISE/NFE/4 Draft
3、for comment 09/30200283 DCPublication historyFirst published September 2009Amendments issued since publicationDate Text affected BRITISH STANDARD BSI 2009 iBS 7996:2009ContentsForeword iii1 Scope 12 Normative references 13 Terms, definitions, abbreviations and symbols 14 Preparation for calibration
4、45 Calibration procedure 96 Calculation of results 117 Classification of torque measuring devices 138 Calibration certificate 15AnnexesAnnex A (informative) Orientation diagrams 16Annex B (informative) Method example of determining uncertainty of the calibration results of the torque measuring devic
5、e 19Annex C (informative) Bandwidth 27Bibliography 28List of figuresFigure A.1 Continuous application of torque 16Figure A.2 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 17Figure A.3
6、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 17Figure A.4 Example of preloading and calibration sequences for a torque measuring device with square drives, six increasing and decreasing torques
7、, classes 0.05 to 5.0 17Figure A.5 Example of preloading and calibration sequences for a torque measuring device with square drives, six increasing torques only, classes 0.05 to 5.0 17Figure A.6 Example of preloading and calibration sequences for a torque measuring device, six increasing and decreas
8、ing torques, classes 0.2 to 5.0 18Figure A.7 Example of preloading and calibration sequences for a torque measuring device, six increasing torques only, classes 0.2 to 5.0 18Figure B.1A Worked example in torque units: 100 Nm torque measuring device clockwise torque, increasing series only 22Figure B
9、.1B Worked example in torque units: 100 Nm torque measuring device clockwise torque, increasing series only 22Figure B.1C Worked example in torque units: 100 Nm torque measuring device clockwise torque, increasing series only 23Figure B.2 Worked example in torque units: Expanded uncertainty as a fun
10、ction of applied torque 23Figure B.3 Worked examples in torque units: Deviation as a function of applied torque 23Figure B.4A Worked example in mV/V: 2 kNm torque measuring device clockwise torque, increasing and decreasing series 24Figure B.4B Worked example in mV/V: 2 kNm torque measuring device c
11、lockwise torque, increasing and decreasing series 25Figure B.4C Worked example in mV/V: 2 kNm torque measuring device clockwise torque, increasing and decreasing series 25Figure B.5 Worked example in mV/V: Expanded uncertainty as a function of applied torque 26Figure B.6 Worked example in mV/V: Devi
12、ation as a function of applied torque 26BS 7996:2009ii BSI 2009BRITISH STANDARDList of tablesTable 1 Uncertainty of calibration torques 5Table 2 Criteria for classification of torque measuring devices 14Summary of pagesThis document comprises a front cover, an inside front cover, pages i to iv, page
13、s 1 to 28, an inside back cover and a back cover.BRITISH STANDARD BSI 2009 iiiBS 7996:2009ForewordPublishing informationThis British Standard is published by BSI and came into effect on 30 September 2009. It was prepared by Subcommittee ISE/NFE/4/1, Uniaxial testing of metals, under the authority of
14、 Technical Committee ISE/NFE/4, Mechanical testing of metals. A list of organizations represented on these committees can be obtained on request to their secretary.Information about this documentThis British Standard describes a method of calibration and classification only and should not be used or
15、 quoted as a specification. It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and competent people.Presentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type. Its require
16、ments are expressed in sentences in which the principal auxiliary verb is “shall”.Commentary, explanation and general informative material is presented in notes in smaller italic type, and does not constitute a normative element.Contractual and legal considerationsThis publication does not purport t
17、o 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.BS 7996:2009iv BSI 2009BRITISH STANDARDThis page deliberately left blankBRITISH STANDARD BSI 2009 1BS 7996:20091 Sc
18、opeThis British Standard specifies a method for the calibration and classification of torque measuring devices using continuous torque application where the inertial effects are minimal. This includes torque measuring devices used for the calibration of hand torque tools conforming to BS EN ISO 6789
19、, and torque measuring devices conforming to BS 7882.The information to be given on the certificate of calibration is also specified in this standard. Annex A provides diagrams of the continuous application of torque, and examples for the calibration of torque measuring devices. Annex B gives an exa
20、mple of determining uncertainty of the calibration results of the torque measuring device. Annex C shows how to calculate mechanical and electronic bandwidth.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only th
21、e edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.BS 7882, Method for the calibration and classification of torque measuring devicesBS EN ISO 6789, Assembly tools for screws and nuts Hand torque tools Requirements and te
22、st methodsJCGM 200, International vocabulary of metrology Basic and general concepts and associated terms (VIM) (third edition available at: http:/www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf)3 Terms, definitions, abbreviations and symbolsFor the purposes of this British Standard, the
23、terms and definitions given in JCGM 200 and the following apply.3.1 acceleration periodtime interval during which the rate of change of applied torque starts from zero and then attains a constant value3.2 bandwidth of the reference standardBRSresponse of the reference standard to a step input (expre
24、ssed in hertz)NOTE See Annex C.3.3 bandwidth of the torque measuring deviceBTMDresponse of the torque measuring device to a step input (expressed in hertz)NOTE See Annex C.BS 7996:20092 BSI 2009BRITISH STANDARD3.4 calibration torqueTtorque, with traceability derived from national standards of mass,
25、length and time, and of specified uncertainty of measurement, which can be applied to the torque measuring device3.5 constant rate period time interval between the acceleration and deceleration periods at which the rate of change of applied torque is constant3.6 continuous application of torqueseque
26、nce consisting of three time periods: acceleration period, constant rate period and deceleration periodNOTE Refer to Figure A.1.3.7 data acquisition systemelectronic module that has the ability to transfer, store, amplify and filter signals from a torque measuring device NOTE Where analogue signals
27、are acquired by the torque measuring device, and these are converted into a digital data stream using an analogue to digital converter, the stream of data may be digitally filtered, resampled and stored, or logged ready for analysis.3.8 data skewchange in applied torque during the period between nom
28、inally synchronized readings from the reference standard and the torque measuring device NOTE This period can be due to the readings being taken at different times or propagation delays. It can be determined, at various stable torque values throughout the torque calibration range, by applying a shar
29、p mechanical stimulus to the system and measuring the difference in response times of the outputs from the reference standard and the torque measuring device.3.9 deceleration periodtime interval during which the rate of change of applied torque decreases from a constant value to zero3.10 deflectiond
30、algebraic difference between the indicator reading prior to the application of a torque and the indicator reading for each applied torque in a given measurement series NOTE The deflection may be derived from either digital data output or visual data output.3.11 loading directiondirection of applied
31、torque, either clockwise or anti-clockwise about the axis of rotation, when viewed from the end of the torque measuring device to which the calibration torque is applied3.12 lower limit of calibrationTminlower value of torque at which a torque measuring device of a given class can be calibrated3.13
32、maximum calibration torqueTmaxupper calibration torque value applied to the torque measuring deviceBRITISH STANDARD BSI 2009 3BS 7996:20093.14 rate of applied torqueRTchange of torque with time3.15 recording rateRrrate at which the visual or digital output is recorded for subsequent analysisNOTE 1 T
33、he data may be manually recorded or recorded by an optical recognition system, i.e. video, for subsequent analysis.NOTE 2 The recording rate is sometimes known as the refresh rate.3.16 reference standardRSequipment used to generate or to measure the reference torque applied to the torque measuring d
34、evice that is being calibratedNOTE Torques may be generated by a power source monitored by the reference standard. 3.17 relative error of indicationEimean deflection for a given value of increasing torque minus the corresponding value of applied torque NOTE 1 For the purposes of this standard, relat
35、ive 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.3.18 relative error of interpolationEitdifference between the value of the mean deflection for a given value of increasing torque and the
36、 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 interpolation is expressed as a percentage of the computed deflection for the given increasing torque.3.19 relative repeatabilityR
37、1closeness of the agreement between the results of two successive measurements from the same applied torque, carried out under the same conditions of measurement3.20 relative reproducibilityR2closeness of agreement between the results of successive measurements from the same applied torque, carried
38、out under changed conditions of measurement3.21 relative residual deflectionR0maximum residual deflection obtained from all the series of torques NOTE For the purposes of this standard, relative residual deflection is expressed as a percentage of the mean deflection for the maximum torque applied.BS
39、 7996:20094 BSI 2009BRITISH STANDARD3.22 relative reversibilityR3difference between the deflection obtained from the last given torque series applied in an increasing mode and the deflection obtained from the same given torque applied in a decreasing modeNOTE For the purposes of this standard, relat
40、ive reversibility is expressed as a percentage of the deflection of the last series for the given torque, applied in an increasing mode.3.23 residual deflectiond0algebraic difference between the indicator readings before and after the application of a single series of torques3.24 resolutionrsmallest
41、 discernible measurement interval on the torque measuring device indicator3.25 sampling rate rate at which the analogue to digital converter samples a waveformNOTE The analogue waveform may be sampled at a much higher rate than the rate at which data is available.3.26 torqueproduct of tangential for
42、ce and length applied about a known centre of rotation 3.27 torque measuring deviceTMDsystem comprising electrical, electronic, mechanical, hydraulic or optical torque device, with associated instrumentation, including the automated logging of data when part of the device4 Preparation for calibratio
43、n4.1 Reference standard 4.1.1 Uncertainty of calibration torquesValues for the maximum permissible uncertainty of the calibration torques 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
44、 is used to determine a calibration torque, it shall conform to Table 1.The uncertainty of the calibration torque shall take into account factors such as bandwidth of the system and its own calibration traceability.BRITISH STANDARD BSI 2009 5BS 7996:2009Table 1 Uncertainty of calibration torquesClas
45、s of torque measuring device to be calibratedMaximum permissible uncertainty of calibration torque applied A)0.05 null0.010.1 null0.020.2 null0.040.5 null0.101.0 null0.202.0 null0.405.0 null1.00A)Using a coverage factor of k = 2 to give a confidence level of approximately 95%.4.1.2 Traceability of m
46、easurementsAll definitive measurements, such as mass, length, time and temperature, shall be traceable to national standards; evidence of this shall be provided by a certificate of calibration.4.1.3 BandwidthThe bandwidth of the reference standard shall be determined.Two bandwidth contributions shal
47、l be taken into consideration:a) mechanical: this is controlled by the natural frequency of the sensing element, i.e. transducer (see C.1); b) electronic: this is a function of the instrumentation used (see C.2).The bandwidth of the reference standard shall be taken as the lower of these two values.
48、4.2 Condition and identification of a torque measuring device4.2.1 Calibration shall not be commenced unless the torque measuring device is considered 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 or
49、der includes the drive components being of a sufficiently good fit to exert a minimum bias on the system.4.2.2 All parts of the torque measuring device shall be identified in accordance with 4.2.1, including the following, where applicable:a) signal cables;b) switch boxes; c) interfaces; d) data acquisition systems; e) computers; and f) software (where information is available).BS 7996:20096 BSI 2009BRITISH STANDARD4.2.3 Where an electrical indicator used with a torque measuring device is replaced with
