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1、BRITISH STANDARD BS 6955-1: 1994 ISO 5347-1: 1993 Calibration of vibration and shock pick-ups Part 1: Methods for primary vibration calibration by laser interferometry UDC 534.1:681.327.7:53.089.6 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:16:38 GMT+00:00 2006, Uncontrolled Copy, (c)
2、BSI BS 6955-1:1994 This British Standard, having been prepared under the direction of the General Mechanical Engineering Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 March 1994 BSI 11-1999 The following BSI references relate to the
3、work on this standard: Committee reference GME/21 Draft for comment 87/72304 DC ISBN 0 580 23080 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee G
4、ME/21, upon which the following bodies were represented: Electricity Association Federation of Civil Engineering Contractors Imperial College of Science and Technology Institute of Sound and Vibration Research Institution of Mechanical Engineers Lloyds Register of Shipping Ministry of Defence Open U
5、niversity Power Generation Contractors Association PGCA (BEAMA Ltd.) Railway Industry Association of Great Britain Sira Test and Certification Ltd. Society of British Aerospace Companies Limited The following bodies were also represented in the drafting of the standard, through subcommittees and pan
6、els: British Coal Corporation Health and Safety Executive Society of Environmental Engineers University of Cranfield Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:16:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6955-1:1994 BSI
7、11-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Apparatus1 3Ambient conditions2 4Preferred amplitudes and frequencies2 5Method 12 6Method 23 Annex A (normative) Calculation of uncertainty6 Annex B (normative) Formulae for the calculation of acceleration9
8、Figure 1 Measuring system for the fringe-counting method (Method 1)3 Figure 2 Measuring system for the minimum-point method (Method 2)5 Table 1 Displacement amplitudes for minimum points4 Table B.1 Values for Jn for zero points of the Bessel function10 Licensed Copy: sheffieldun sheffieldun, na, Tue
9、 Dec 05 05:16:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6955-1:1994 ii BSI 11-1999 National foreword This Part of BS 6955 has been prepared under the direction of the General Mechanical Engineering Standards Policy Committee. It is identical with ISO 5347-1:1993 Methods for the calibration of
10、 vibration and shock pick-ups Part 1: Primary vibration calibration by laser interferometry published by the International Organization for Standardization (ISO). ISO 5347-1 was prepared by Technical Committee ISO/TC 108, Mechanical vibration and shock, in which the UK played an active part. BS 6955
11、 consists of the following Parts, which are identical with the corresponding Parts of ISO 5347: Part 0: Guide to basic principles; Part 1: Methods for primary vibration calibration by laser interferometry; Part 2: Method for primary shock calibration by light cutting; Part 3: Method for secondary vi
12、bration 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 centrifuge; Part 8: Method for primary calibration by dual centri
13、fuge; 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 transverse shock sensitivity; Part 13: Method of test for b
14、ase 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 test for fixed temperature sensitivity; Part 18: Method o
15、f 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 Part 20 of BS 6955. A British Standard does not purport to include all the necessary provis
16、ions 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. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10 and
17、 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. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:16:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6955-1:1
18、994 BSI 11-19991 1 Scope ISO 5347 comprises a series of documents dealing with methods for the calibration 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 calibration of rectilinear accelerometers u
19、sing laser interferometry for dynamic displacement measurements. It is applicable for a frequency range from 20 Hz to 5 000 Hz and a dynamic range from 10 m/s2 to 1 000 m/s2 (frequency-dependent). The limits of uncertainty applicable are as follows: 0,5 % of reading at reference frequency (160 Hz or
20、 80 Hz) and reference amplitude (100 m/s2 or 10 m/s2) and reference amplifier gain setting; 1 % of reading for frequencies u 1 000 Hz; 2 % of reading for frequencies 1 000 Hz. 2 Apparatus 2.1 Equipment capable of maintaining the ambient conditions, within the requirements specified in clause 3. 2.2
21、Frequency generator and indicator, having the following characteristics: uncertainty, for frequency: maximum 0,01 % of reading; frequency stability: better than 0,01 % of reading over the measurement period; amplitude stability: better than 0,01 % of reading over the measurement period. 2.3 Power am
22、plifier/vibrator combination, having the following characteristics: total distortion: 2 % maximum; transverse, bending and rocking acceleration: kept to a minimum, maximum 10 % of the acceleration in the intended direction at frequencies used; above 1 000 Hz, a maximum of 20 % is permitted; hum and
23、noise: 70 dB min. below full output; acceleration amplitude stability: better than 0,05 % of reading over the measurement period. The attachment surface shall not introduce base strain to the accelerometer. 2.4 Seismic block for vibrator and laser interferometer (the same block), with a mass at leas
24、t 2 000 times the mass of moving elements of vibrator, fixture and transducer. The seismic block shall be suspended by low damped springs. If floor vibrations influence, the suspension resonance frequency vertically and horizontally shall be 2 Hz. 2.5 Laser, of helium-neon type; in laboratory condit
25、ions of air pressure 100 kPa, temperature 23 C and relative humidity 50 % the wavelength is 0,632 8 4m, which value is used in this part of ISO 5347. If the laser has manual or automatic atmospheric compensation, this shall be set to zero or switched off. 2.6 Interferometer, of Michelson type, with
26、light detector for sensing the interferometer bands and having a frequency response from d.c. to 15 MHz. 2.7 Counting instrumentation, (for Method 1, frequency range from 20 Hz to 800 Hz), having the following characteristics: frequency range: 10 Hz to 20 MHz; uncertainty, maximum: 0,01 % of reading
27、. The counter can be substituted by a ratio counter having the same uncertainty. 2.8 Tunable band-pass filter or spectrum analyser, (for Method 2, frequency range from 1 000 Hz to 5 000 Hz), having the following characteristics: frequency range: 100 Hz to 10 000 Hz; bandwidth: 12 % of centre frequen
28、cy; filter slopes: better than 24 dB/octave; signal-to-noise ratio: better than 70 dB below maximum signal; dynamic range: better than 60 dB. 2.9 Instrumentation for zero detection, (for Method 2 not needed with spectrum analyser), with a frequency range from 30 Hz to 5 000 Hz. The range shall be su
29、fficient for detection of output noise from the bandpass filter. 2.10 Voltage instrumentation, measuring true r.m.s. accelerometer output, having the following characteristics: frequency range: 20 Hz to 5 000 Hz; uncertainty, maximum 0,01 % of reading; below 40 Hz: 0,1 %. The r.m.s. value shall be m
30、ultiplied by a factor of to obtain the (single) amplitude used in the formulae. 2.11 Distortion-measuring instrumentation, capable of measuring total distortion of 0 to 5 % and having the following characteristics: frequency range: 5 Hz to 10 kHz; uncertainty, maximum: 10 % of reading. 2 Licensed Co
31、py: sheffieldun sheffieldun, na, Tue Dec 05 05:16:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6955-1:1994 2 BSI 11-1999 2.12 Oscilloscope (optional), for checking the waveform of the accelerometer signal, with a frequency range from 5 Hz to 5 000 Hz. 2.13 Other apparatus requirements In order t
32、o achieve the required 0,5 % accuracy, the accelerometer and accelerometer amplifier shall be considered as one unit and calibrated together. The accelerometer shall be structurally rigid. The base strain sensitivity shall be 0,2 108m/s2 at a base strain of 2,5 104m/s2, the transverse sensitivity sh
33、all be 1 % and the stability of the accelerometer/amplifier combination shall be better than 0,2 % of the reading per year. 3 Ambient conditions Calibration shall be carried out in the following ambient conditions: room temperature: (23 3) C; air pressure: (100 5) kPa; relative humidity: (50 25) %.
34、4 Preferred amplitudes and frequencies Six amplitudes and six frequencies equally covering the accelerometer range shall be chosen from the following series: a) Acceleration (Method 1 only), in metres per square second: 10, 20, 50, 100, 500; reference acceleration 100 m/s2 (second choice: 10 m/s2).
35、b) Frequency, in hertz: 20, 40, 80, 160, 315, 630, 1 250, 2 500, 5 000; reference frequency 160 Hz (second choice: 80 Hz). 5 Method 1, for frequency range from 20 Hz to 800 Hz 5.1 Test procedure After optimizing the interferometer (2.6) settings, determine the reference calibration factor at prefera
36、bly 160 Hz (second choice: 80 Hz), 100 m/s2 (second choice: 10 m/s2) and the standard position of amplifier range switch by measuring either the fringe frequency with the counter (2.7) the fringe-counting method in accordance with Figure 1 shall be used or the ratio between the vibration frequency a
37、nd the fringe frequency with a ratio counter (2.7). Then determine the calibration factor at the other selected standard acceleration levels and frequencies. The results shall be given as a percentage deviation from the reference calibration factor. For every frequency and acceleration combination,
38、the distortion, the transverse, bending and rocking accelerations, hum and noise shall be measured and the values shall be within the limits specified in 2.3. 5.2 Expression of results (see also B.1, Annex B) Calculate the acceleration amplitude, a, of the accelerometer, expressed in metres per seco
39、nd squared, from the fringe frequency readings using the following formula: a = 3,122 8 106 f ff and calculate the calibration factor, S, from the following formula: If a ratio counter is used, calculate the acceleration amplitude, a, expressed in metres per second squared, using the following formu
40、la: a = 3,122 8 106 f2 Rf and calculate the calibration factor, S, from the following formula: where Rf is the ratio between the vibration frequency and the fringe frequency, ff, over at least 100 vibration periods. When the calibration results are reported, the total uncertainty of the calibration
41、and the corresponding confidence level, calculated in accordance with Annex A, shall also be reported. A confidence level of 99 % shall be used (second choice: 95 % confidence level). where Vis the accelerometer output, in volts (single) amplitude; fis the frequency of the vibrator, in hertz; ffis t
42、he number of fringe signal periods over a time period which is long compared with the vibration period the number of periods is divided by the time in order to obtain the fringe frequency in hertz; S0,320 2106= V fff - S0,320 2106= V f 2 Rf - Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05
43、:16:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6955-1:1994 BSI 11-19993 6 Method 2, for frequency range from 800 Hz to 5 000 Hz 6.1 Test procedure Filter the signal from the light detector (2.6) through a bandpass filter (2.8) with the centre frequency equal to the accelerometer frequency. Thi
44、s filtered signal has a number of minimum points at accelerometer displacements in accordance with Table 1. After setting the frequency, adjust the vibrator amplitude from zero to the value at which the filtered light detector signal, after reaching maximum value, returns to a minimum value. This mi
45、nimum value is minimum point No. 1, at which the amplitude is 0,193 0 4m. The amplitude for the other minimum points in order can be taken from Table 1. The measuring system for the minimum point method is shown in Figure 2. Figure 1 Measuring system for the fringe-counting method (Method 1) License
46、d Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:16:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6955-1:1994 4 BSI 11-1999 Table 1 Displacement amplitudes for minimum points 6.2 Expression of results (see also B.2, Annex B) Calculate the acceleration, a, expressed in metres per second squared,
47、 from the following formula: a = 39,478 106 d f2 and calculate the calibration factor, S, from the following formula: The different calibration factors determined are used to calculate the deviations relative to the 160 Hz (80 Hz)/100 m/s2(10 m/s2) value obtained in accordance with Method 1 (see cla
48、use 5). When the calibration results are reported, the total uncertainty of the calibration and the corresponding confidence level, calculated in accordance with Annex A, shall also be reported. A confidence level of 99 % (second choice: 95 % confidence level) shall be used. Minimum point No. Displa
49、cement amplitude, d 4m 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 0 0,193 0 0,353 3 0,512 3 0,670 9 0,829 4 0,987 8 1,146 1 1,304 4 1,462 7 1,621 0 1,779 2 1,937 5 2,095 7 2,253 9 2,412 2 2,570 4 2,728 6 2,886 8 3,045 0 3,203 3 3,361 5 3,519 7 3,677 9 3,836 1 3,994 3 4,152 5 4,310 7 4,468 9 4,627 1 4,785 3 where Vis the accelerometer output, in volts