1、BRITISH STANDARD BS 6955-10: 1994 ISO 5347-10: 1993 Calibration of vibration and shock pick-ups Part 10: Method for primary calibration by high impact shocks UDC 534.1:681.327.7:53.089.6BS6955-10:1994 This British Standard, having been prepared under the directionof the General Mechanical Engineerin
2、g Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes intoeffecton 15March1994 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference GME/21 Draft for comment 87/72304 DC ISBN 0 580 23082 1 Committees responsible for
3、this British Standard The preparation of this British Standard was entrusted by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee GME/21, upon which the following bodies were represented: Electricity Association Federation of Civil Engineering Contractors I
4、mperial College of Science and Technology Institute of Sound and Vibration Research Institution of Mechanical Engineers Lloyds Register of Shipping Ministry of Defence Open University Power Generation Contractors Association PGCA (BEAMA Ltd.) Railway Industry Association of Great Britain Sira Test a
5、nd Certification Ltd. Society of British Aerospace Companies Limited The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Coal Corporation Health and Safety Executive Society of Environmental Engineers University of Cranfield Amendment
6、s issued since publication Amd. No. Date CommentsBS6955-10:1994 BSI 09-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative reference 1 3 Apparatus 1 4 Preferred pulse durations and accelerations 2 5 Method 2 Annex A (normative) Formulae for the c
7、alculating of acceleration 3 Annex B (normative) Calculation of uncertainty 4 Figure A.1 3 List of references Inside back coverBS6955-10:1994 ii BSI 09-1999 National foreword This Part of BS 6955 has been prepared under the direction of the General Mechanical Engineering Standards Policy Committee.
8、It is identical with ISO5347-10:1993 Methods for the calibration of vibration and shock pick-ups Part 10: Primary calibration by high impact shocks, published by the International Organization for Standardization (ISO). ISO 5347-10 was prepared by Technical Committee ISO/TC108, Mechanical vibration
9、and shock, in which the UK played an active part. BS 6955 consists of the following Parts, which are identical with the corresponding Parts of ISO5347: Part 0: Guide to basic principles; Part 1: Methods for primary vibration calibration by laser interferometry; Part 2: Method for primary shock calib
10、ration by light cutting; Part 3: Method for secondary vibration calibration; Part 4: Method for secondary shock calibration; Part 5: Method for calibration by Earths gravitation; Part 6: Method for primary vibration calibration at low frequencies; Part 7: Methods for primary calibration by centrifug
11、e; Part 8: Method for primary calibration by dual centrifuge; Part 9: Method for secondary vibration calibration by comparison of phase angles; Part 10: Method for primary calibration by high impact shocks; Part 11: Method of test for transverse vibration sensitivity; Part 12: Method of test for tra
12、nsverse shock sensitivity; Part 13: Method of test for base strain sensitivity; Part 14: Method of test for resonance frequency of undamped accelerometers on a steel block; Part 15: Method of test for acoustic sensitivity; Part 16: Method of test for mounting torque sensitivity; Part 17: Method of t
13、est for fixed temperature sensitivity; Part 18: Method of test for transient temperature sensitivity; Part 19: Method of test for magnetic field sensitivity. Part 20 of ISO 5347 is in preparation. It is envisaged that when it is published it will be implemented as Part20of BS6955. A British Standard
14、 does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International Standard Corresponding Britis
15、h Standard ISO 5347-1:1993 BS 6955 Calibration of vibration and shock pick-ups Part 1: 1994 Methods for primary vibration calibration by laser interferometry (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 6, an inside back cover a
16、nd a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6955-10:1994 BSI 09-1999 1 1 Scope ISO 5347 comprises a series of documents dealing with methods for the calibratio
17、n of vibration and shock pick-ups. This part of ISO 5347 lays down detailed specifications for the instrumentation and procedure to be used for primary high impact shock calibration of accelerometers. It applies to rectilinear accelerometers, mainly of the piezoelectric and piezoresistive type, to p
18、rimary standards and working accelerometers. This part of ISO 5347 is applicable for a time range from104s to1004s and a dynamic range from10 3 m/s 2to10 5 m/s 2 . The limit of uncertainty applicable is 10% of reading. 2 Normative reference The following standard contains provisions which, through r
19、eference in this text, constitute provisions of this part of ISO5347. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO5347 are encouraged to investigate the possibility of applying the most recent
20、edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 5347-1:1993, Methods for the calibration of vibration and shock pick-ups Part 1: Primary vibration calibration by laser interferometry. 3 Apparatus 3.1 Equipment capable
21、 of maintaining room temperature at23 C 3 C. 3.2 High impact shock machine, with two long thin steel rods, one acting as a hammer and the other as an anvil to which the accelerometer is attached. The hammer-rod can be shot or permitted to fall freely and to strike the anvil-rod which is permitted to
22、 accelerate freely and later to be caught up by a spring or braking device. At the strike, the longitudinal resonance frequency is excited in the anvil-rod. The contact of the two rod surfaces and the cushion material between them shall be made so that the generated stress pulse approximates a half-
23、sine pulse having a duration equal to half the period of resonance of the rod in its fundamental longitudinal mode. A number of anvil-rods shall be used, one for each desired pulse duration. The resonance period of the rod, T, in seconds, can be estimated from the following formula: where l is the r
24、od length, in metres. In order to avoid coupling of reflected stress pulses in the hammer-rod into the anvil-rod at the moment of impact, the length of the hammer-rod should be about half the length of the anvil-rod. Strain gauges, having a maximum effective length of0,3mm, shall be mounted on the a
25、nvil-rod in order to measure strain for acceleration calculations. The centre of the strain gauges shall be applied at a distance of one rod diameter from the end where the accelerometer is mounted. The cross-sectional area of the rod at the point where the strain gauges are applied shall be measure
26、d with an error of less than 1%. The rod mass between the point where the strain gauges are applied and the point at which the accelerometer is mounted and the accelerometer mass shall be determined with an error of less than 1%. 3.3 Acceleration/time and strain/time recording equipment, comprising
27、a digital memory oscilloscope or digital transient recorder for two channels with peak amplitude detector and a three-digit indicator display for peak pulse amplitude, or a strip chart or X-Y recorder to obtain a readout of the stored transient. The equipment shall have the following characteristics
28、: range:0,14s to1004s and0to50V; uncertainty for amplitude: maximum 2% of reading; amplitude linearity:1% max.deviation from best fit line. 3.4 Filters The use of filters shall be avoided. If filters have to be used, the 3 dB lower limiting frequency shall be lower than0,008/T and the 3dB upper limi
29、ting frequency shall be higher than10/T, where T is the pulse duration. 3.5 Strain gauge, with a d.c.voltage supply, and amplifier, with no filtering and having the following characteristics: frequency response: flat within 3dB from0,008/T to10/T, where T is the pulse duration; linearity: better tha
30、n 0,05% from best fit line; amplification tolerance: 0,5% of signal; calibrated amplification ranges within 0,5%.BS6955-10:1994 2 BSI 09-1999 3.6 Other apparatus requirements The accelerometer shall be structurally rigid. The base strain sensitivity shall be 0,2 10 8m/s 2at a base strain of2,5 10 4m
31、/s 2 , the transverse sensitivity 2% and the stability of the accelerometer/amplifier combination shall be better than0,2% of the reading per year. If there are filters in the amplifier, the filter cut-off frequency settings shall comply with the filter settings specified in3.4. The frequency respon
32、se shall be flat within 3 dB from0,008/T to10/T, where T is the pulse duration. 4 Preferred pulse durations and accelerations Shock pulse durations shall be chosen from between104s and1004s. Accelerations shall be chosen from between10 3 m/s 2and10 5m/s 2 . 5 Method 5.1 Test procedure For high impac
33、t shock calibrations, the sinusoidal vibration calibration factor determined according to ISO5347-1 shall be used as reference calibration factor. The shock motion calibrations are then used to measure the amplitude linearity deviations at high accelerations. By using rods of different lengths and c
34、onsequently different resonance frequencies and dropping them from different heights, determine the shock sensitivity at the standard selected shock pulse durations and accelerations and for the standard amplifier range switch positions. The results shall be given as a percentage deviation from the
35、sinusoidal reference calibration factor. 5.2 Expression of results Calculate the acceleration, a str , in metres per second squared, from the strain measurements in accordance with the following formula (see also Annex A): where Calculate the shock sensitivity, S sh , expressed in volts per (metre p
36、er second squared) V/(m/s 2 ), using the following formula: where m 1 , m 2 , E and A are as given above; The acceleration and strain curves shall always be checked directly on an oscilloscope or recorder without filters and amplifiers. NOTE 1If there is a zero shift in the signal, the zero point im
37、mediately before the shock and the shifted zero point immediately after the shock shall be connected by a straight line, this line being the baseline for acceleration determination. When the calibration results are reported, the total uncertainty of the calibration and the corresponding confidence l
38、evel calculated in accordance with Annex B, shall also be reported. A confidence level of95% shall be used. E is the modulus of elasticity, in newtons per square metre; A is the cross-sectional area of the rod, in square metres, at the point where the strain gauges are applied; m 1 is the rod mass,
39、in kilograms, between the point where strain gauges are applied and the transducer; m 2 is the pick-up mass, in kilograms; is the strain as a function of time. peak is the peak value of the strain curve; a peak is the peak value of the acceleration curve, in volts.BS6955-10:1994 BSI 09-1999 3 Annex
40、A (normative) Formulae for the calculating of acceleration A schematic diagram for aid in calculating acceleration from strain measurements is shown in Figure A.1 The mass below the strain gauges shall be considered as being rigid. At the cross-section at the point where the strain gauges are applie
41、d, the following formulae apply; where Figure A.1 F is the force; m 1 is the mass between the strain gauges and the pick-up; m 2 is the mass of the pick-up; A is the cross-sectional area at the point where the strain gauges are applied; E is the modulus of elasticity; is the strain measured by the s
42、train gauges; p is the pressure in pascals.BS6955-10:1994 4 BSI 09-1999 Annex B (normative) Calculation of uncertainty B.1 Calculation of total uncertainty The total uncertainty of the calibration for the specified confidence level (for the purposes of this part of ISO5347, CL =95%), X 95 , shall be
43、 calculated from the following formula: where The random uncertainty for the specified confidence level, X r(95) , is calculated from the following formula: where The systematic errors shall, first of all, be eliminated or corrected. The remaining uncertainty, X s(95) , shall be taken into account b
44、y using the following formula: where B.2 Calculation of the absolute uncertainty for the shock calibration factor, e S,sh , at calibrated levels The absolute uncertainty for the shock calibration factor, e S,sh , in volts per (metre per second squared), at calibrated levels, is calculated by the law
45、 of combination of errors from the following formula: where X r is the random uncertainty; X s is the systematic uncertainty. e r1 , e r1 , etc. are the deviations from the arithmetic mean of single measurements in the series; n is the number of measurements; t is the value from Students distributio
46、n for the specified confidence level and the number of measurements. K equals2,0for the95% confidence level; e S,sh is the absolute uncertainty for the shock calibration factor at calibrated levels, expressed in volts per (metre per second squared) (seeB.2). S sh is the shock sensitivity (amplitude-
47、dependent), in volts per metre second squared; m 1 is the rod mass, in kilograms, between the point where the strain gauges are applied and the accelerometer; is the uncertainty for the rod mass between the point where the strain gauges are applied and the accelerometer, in kilograms; m 2 is the acc
48、elerometer mass, in kilograms; is the uncertainty for the accelerometer mass, in kilograms; E is the modulus of elasticity, in newtons per metre squared; e E is the uncertainty for the modulus of elasticity, in newtons per metre squared; e m 1 e m 2BS6955-10:1994 BSI 09-1999 5 If the accelerometer h
49、as a voltage supply, add the following factor to the above formula. where B.3 Calculation of the total absolute uncertainty for the shock calibration factor, e S,sh,t , outside the calibrated values The absolute uncertainty for the shock calibration factor, calculated in accordance withB.2, is valid only for calibrated values. The total absolute uncertainty for the shock calibration factor, e S,sh,t , in volts per (metre per second squared) outside calibration values is calculated
