Please refer to this standard for details. GB/T 2423.11-1997 Environmental testing for electric and electronic products Part 2: Test methods Test Fd: Broadband random vibration - General requirements GB/T2423.11-1997 Standard download decompression password: www.bzxz.net

GB/T2423.11—1997
This standard is equivalent to the International Electrotechnical Commission standard IEC68-2-34 "Environmental testing Part 2: Test method Test Fd: Broadband random vibration
General requirements" (1973 1st edition) and Amendment No. 1 (August 1983). This standard replaces GB2423.11-82 "Basic environmental testing procedures for electric and electronic products Test Fd: Broadband random vibration test method
General requirements".
Chapters 1 and 2 of this standard are different from Chapters 1 and 2 of GB2423.11—82. GB2423.11—82 rewrites Chapters 1 and 2 of IEC68-2-34 and deletes Appendix A of IEC68-2-34. This standard also adds the content of Amendment No. 1 of the International Electrotechnical Commission to IEC68-2-34 in August 1983. This standard was first issued in 1982, revised for the first time in September 1997, and implemented on October 1, 1998. From the date of implementation of this standard, it will replace GB2423.11-82. Appendix A of this standard is a reminder appendix.
This standard is proposed by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the overall jurisdiction of the Standardization Institute of the Ministry of Electronics Industry. This standard is under the jurisdiction of the National Technical Committee for Environmental Standardization of Electrical and Electronic Products. The drafting units of this standard are: the Standardization Institute of the Ministry of Electronics Industry, the Fifth Institute of the Ministry of Electronics Industry, and the Shanghai Electronic Instrument Standard and Measurement Testing Institute. The main drafters of this standard are: Zhou Xincai, Wang Shurong, Lu Zhaoming, Lin Zongxiang, Xu Ming, etc. 136
GB/T2423.11-1997
IEC Foreword
1. A formal resolution or agreement on a technical issue formulated by a technical committee of the International Electrotechnical Commission with the participation of all national committees that are particularly concerned with the issue. It reflects and expresses the international consensus on the issue as much as possible. 2. These resolutions or agreements are accepted by the National Committees in the form of recommended standards for international use. 3. In order to promote international unification, the International Electrotechnical Commission hopes that all member countries will adopt the contents of the International Electrotechnical Commission recommended standards as their national standards when formulating national standards, as long as the specific national conditions permit. Any differences between the International Electrotechnical Commission recommended standards and national standards should be clearly indicated in the national standards as far as possible. This standard was prepared by the 50A Subcommittee (Shock, Vibration and Other Dynamic Tests) of the 50th Technical Committee (Environmental Testing) of the International Electrotechnical Commission.
The first draft was discussed at the Stockholm Conference in 1968, and the new draft was discussed at the Tehran Conference in 1969. As a result of this meeting, the final draft 50A (Central Office) No. 133 was submitted to the National Committees for voting according to the "six-month method" in February 1971.
The following countries voted explicitly in favor of this standard: Australia
Austria
Belgium
Czechoslovakia
Hungary
Israel
Turkey
1 Introduction
National Standard of the People's Republic of China
Environmental testing for electric and electronic products
Part 2: Test methods
Test Fd: Random vibration wide band-General requirements
GB/T 2423. 11-1997
idt IEC 68-2-34:1973
Replaces GB2423.11--82
Random vibration testing is complex, so the standard is quite large. Therefore, this standard gives the layout of the test method and the basic principles on which it is based in this introduction.
It must be noted that two particularly important terms in the random vibration test problem are frequently mentioned throughout the standard text. In order to enable the reader to better understand the content of this standard, the following definitions are given; Acceleration spectral density acceleration spectral density (ASD) The spectral density of the acceleration variation, expressed in units of acceleration squared per unit frequency. The frequency spectrum of the acceleration spectral density ASDspectrum The way in which the acceleration spectral density varies over the frequency range. 1.1 Test method design
For ease of use, the entire broadband random vibration is divided into four standards: Test Fd: Broadband random vibration
J-General requirements, GB/T2423.11 (IEC68-2-34). Test Fda: Broadband Random Vibration
Test Fdb: Broadband Random Vibration-
High Reproducibility, GB/T2423.12 (IEC68-2-35). -Medium Reproducibility, GB/T2423.13 (IEC68-2-36). Test Fdc: Broadband Random Vibration-Low Reproducibility, GB/T2423.14 (IEC68-2-37). Each of the last three parts constitutes a complete test method, and its appendix contains the recommended verification method. All the information required by the specification writer is included in the test Fd-General Requirements, while the information required by the test engineer is included in the tests Fda, Fdb and Fdc respectively. Appendix A (Suggestive Appendix) of this standard will provide further information. The writer of the specification only needs to read the test Fd: General Requirements, while the test engineer can select the specified test method in Fda, Fdb and Fdc. All users are strongly recommended to read this standard. 1.2 Basic principles of testing
In all national standards for environmental test methods, especially for identification tests or acceptance tests, and for tests that are intended to be carried out by interested parties (such as suppliers and buyers of electronic components) on the same type of test samples, a certain level of reproducibility is required. The term reproducibility used in this standard does not refer to the reproducibility between the test and the actual environment, but to the consistency of the results obtained when the test is carried out by different people in different situations. In order to try to meet the different tolerance ranges in the severity level and to prove the great differences in the effectiveness of the test, three types of reproducibility are quoted (see Chapter 5). When studying the dynamic characteristics of the test sample and the suitability of the test equipment, a verification method can be selected within each reproducibility. Approved by the State Administration of Technical Supervision on September 1, 1997 138
Implementation on October 1, 1998
GB/T2423.11--1997
The relevant specifications should state the reproducibility suitable for specific requirements, and leave the choice of verification method to the laboratory. For a given reproducibility, the tolerances should be chosen so that each verification method will give approximately equal results. Reproducibility requires that the vibration level be controlled within a narrow frequency band. Although narrowband equalization gives better reproducibility than a wideband system, it makes it difficult for the test specimen to reflect the test environment. However, wideband equalization allows resonances within the test specimen to change the test level, thereby producing peaks and valleys. In use, as the test specimen responds to its environment, it will also produce peaks and valleys, but it may not be possible to make such peaks and valleys match those produced in the test chamber. For informational purposes, the specification may specify that a narrowband analysis be continued after a low reproducibility test suitable for the method. Experience with random vibration testing enables the test engineer to better use existing test equipment, but it cannot be overemphasized that engineering judgment must be allowed in its application if the level applied in the random vibration test is to be proven to be a reasonable practical level. This applies to the selection of verification methods, fixture design, and general interpretation of the results. 2 Purpose
To determine the ability of components and equipment to withstand random vibration of specified severity levels. Random vibration tests are applicable to components and equipment that may be affected by random vibration conditions during use. The purpose of the test is to determine whether mechanical weaknesses and/or specified performance have been degraded, and to use this information in conjunction with relevant specifications to determine whether the test sample is acceptable. When conducting the vibration stress (conditional test) specified in this test, the test sample is subjected to a random vibration test of a given level within a wide frequency band. Since the test sample and its fixture will produce complex mechanical responses, this test requires special attention to the preparation, conduct and verification of the specified requirements.
3 Installation and control
3.1 Installation of test samples
The test sample shall be in accordance with GB/T2423.43-1995 (idtIEC68-2-47) "Installation requirements and guidelines for components, equipment and other products in dynamic tests such as impact (Ea), collision (Eb), vibration (Fc and Fd) and steady-state acceleration (Ga)" are installed on the test equipment.
3.2 Reference points and control points
Measurements made at reference points (in some cases, at various control points related to the fixed points of the test sample) are used to verify the test requirements. For high reproducibility, it is necessary to measure at the control points. For centering and low reproducibility, measurements are required at a hypothetical point. If many small test samples are installed on a fixture, when the lowest resonant frequency of the load fixture exceeds the test upper limit frequency f, it can be considered that the reference point and (or) control point are related to the fixture, and have nothing to do with the fixed point of the test sample (that is, the fixed points of the fixture and the vibration table are selected as reference points and (or) control points, rather than the fixed points of the test sample and the fixture). 3.2.1 Fixing points
Fixing points are defined as those parts of the test specimen that are in contact with the fixture or shaker and are usually the points at which the test specimen is normally fastened in use. If parts of the actual mounting structure are used as fixtures, then the fixing points of these mounting structures should be used as fixing points instead of the fixing points of the test specimen.
3.2.2 Control points
Control points are usually fixing points. Control points should be as close as possible to the fixing points and in any case their connection to the fixing points should be rigid. If there are four or fewer fixing points, then each fixing point is used as a control point. If there are more than four fixing points, then the relevant specification needs to specify four representative fixing points as control points. NOTE
1 For large and/or complex test specimens, it is an important issue to specify the individual control points in the relevant specification. 2 Tolerances are only specified for individual control points with high reproducibility. 3.2.3 Reference point
GB/T2423.11—1997
The reference point is a single point used to obtain the reference signal to verify the test requirements and represent the movement of the test sample. It can be a control point or a hypothetical point established by processing the signals of each control point manually or automatically. If the hypothetical point is used, the spectrum of the reference signal is defined as the arithmetic mean of the acceleration spectrum density values ​​of all control point signals at each frequency. In this case, the total root mean square value of the signal is equal to the root mean square of the root mean square value of the signal from each control point. The relevant specifications should specify the reference point used, or explain how to select the reference point. It is recommended to use hypothetical reference points for large and (or) complex test samples. Note: For the verification of the total root mean square acceleration, it is allowed to use the swept frequency technology to automatically process the signals from each control point to establish hypothetical points. However, if the error source (for example: analyzer bandwidth, sampling time, etc.) is not corrected, it cannot be used to verify the acceleration spectrum density value. 4 Severity Level
This test uses a combination of the following parameters to specify the severity level of vibration: - frequency range (~f);
acceleration spectrum density level;
duration of the conditional test.
For each parameter, the relevant specification should select the appropriate requirement based on the values ​​given below. The frequency range and the acceleration spectrum density level together specify the total root mean square value of the test. The range of these values ​​is shown in Table 4a and Table 4b. For simplicity, this test specifies a flat spectrum. In special cases, a shaped spectrum can be specified accordingly. In this case, the relevant specification should specify the spectral shape of the acceleration spectrum density as a function of frequency. For special considerations for this case, see the notes to 4.1, 4.2 and 5.1.
4.1 Frequency Range
The relevant specification should select a frequency range from Table 1: Table 1
If necessary, the relevant specification may specify fi as 5Hz or 10Hz. In special cases, the relevant specification may specify. as 200Hz. If necessary, the relevant specifications may stipulate that f is 50Hz. The relationship between the frequency f1 and ? and the frequency spectrum of the acceleration spectrum density is shown in Figure 1. Note: In special cases, if the shaped spectrum of the acceleration spectrum density must be specified, the frequency range should still be taken from Table 1 as much as possible. 140
GB/T2423.11---1997
Specified frequency range
6dB/oct
272 (logarithmic scale)
Mi upper tolerance limit, medium reproducibility; M2-lower tolerance limit, medium reproducibility; H,-upper tolerance limit, high reproducibility; H,-lower tolerance limit, high reproducibility; N-specified acceleration spectrum density (nominal spectrum) Figure 1 Spectrum and tolerance range of acceleration spectrum density 4.2 Level of acceleration spectrum density spectrum
The level of acceleration spectrum density spectrum between f1 and f2 should be selected from the following values ​​(0dB, see Figure 1): 0. 05(m/s*)°/Hz
0. 1(m/s2)°/Hz
0. 2(m/s2)2/Hz
0. 5(m/s2)*/Hz
1. 0(m/s*)*/Hz
2. 0(m/s*)2/Hz
5. 0(m/s)2/Hz
10. 0(m/s2)2/Hz
20. 0(m/s*)2/Hz
50.0(m/s2)2/Hz
100(m/s2)2/Hz
200(m/s2)2/Hz
500(m/s2)2/Hz
1 000(m/s*)2/Hz
Note: In special cases, if it is necessary to specify a spectrum with two or more acceleration spectrum density levels, its value should still comply with the above provisions as much as possible.
4.3 Duration of conditional test
The duration should be selected from the following times. If the specified duration is equal to or greater than 10h in each direction, then this time can be divided into a cycle of 5h. However, the stress in the test sample (such as thermal stress, etc.) cannot be reduced. The following duration is the total time of the conditional test and should be evenly distributed between the specified directions. 30s
5 Reproducibility level
90 min
5.1 Tolerance representing reproducibility level
In the specified frequency range of ~f, the reproducibility is specified by the tolerance of the corresponding direction given in Table 2. The tolerances listed in the table are expressed in decibels of the specified acceleration spectrum density level and the corresponding total root mean square. 141
GB/T 2423. 11---1997
For high reproducibility, lateral measurements should be made in two mutually perpendicular transverse directions at the control point farthest from the center of the mounting plane. For large structures, it is recommended to measure the lateral acceleration at more than one control point. The acceleration spectral density outside the specified frequency range ~f, should be as low as possible. Beyond the upper frequency limit f? up to 2f:, high reproducibility requires that the frequency spectrum of the acceleration spectral density be lower than the -6dB/oct slope shown in Figure 1. In addition, the root mean square acceleration in the frequency band f~10f or below 10kHz (the smaller one) should not exceed 25% (-12dB) of the total root mean square acceleration within the specified frequency range.
For center reproducibility, when f2 is exceeded, the acceleration spectral density is not limited, and the RMS acceleration in the frequency band f2 to 10f, or below 10kHz (the smaller one) shall not exceed 70% (-3dB) of the total RMS acceleration in the specified frequency range. For low reproducibility, when f is exceeded, neither the acceleration spectral density nor the total RMS acceleration is limited. Below the lower frequency f, for any reproducibility, neither the acceleration spectral density nor the total RMS acceleration is limited. Note
If in special cases, a flat spectrum such as velocity spectral density cannot be used, the relevant specification may specify the use of a nominal shaped spectrum, in which case the tolerance band in Figure 1 should still be used as much as possible.
When two or more levels of acceleration spectral density are specified, the relevant specification should specify that the slope of the transition from one level to another (because spectra with large slopes are difficult to obtain and verify) should not be required to be greater than 24dB/oct. Table 2
Tolerance range
Reproducibility
High reproducibility
Medium reproducibility
Low reproducibility
Reference point
True value of acceleration spectrum density
Predetermined direction
Each control point
Each control point
True value of total RMS acceleration in predetermined direction (fr～f2)
Reference point
Note: There is no specified tolerance for the true value of the low reproducibility acceleration spectrum density. However, the tolerance of the indicated value given by the analytical instrument used shall not be greater than ±3dB. 5.2 Choice of Reproducibility
The specification should specify the reproducibility required for the test. The classification of reproducibility only represents a measure of the reproducibility that can be expected from one laboratory to another.
When a low reproducibility test is required, the writer of the specification may specify the maximum permissible bandwidth of the equalizer and/or analyzer used. In any case, the bandwidth of the analyzer should not be greater than 100 Hz or one-third octave, whichever is greater. When a wider bandwidth system is specified, the reproducibility obtained by this test is poorer, but it may be simpler and cheaper than other methods. It should be noted that the low reproducibility test does not require the use of sinusoidal vibrations to measure the frequency response. High reproducibility tests give relatively high reproducibility, but are generally more complicated and may require more expensive and advanced test equipment. They also take longer to test because of the additional tests required. High reproducibility tests should only be required when absolutely necessary. It is important that the writer of the specification consider these factors and select a reproducibility that is not higher than that necessary for the recommended application of the test sample.
6 Sinusoidal vibration
6.1 Frequency response measurement
For high and medium reproducibility, the test specimens are subjected to a sinusoidal vibration test for the frequency response measurement. In this case, a sine sweep is applied in both the positive and negative directions over the entire frequency range with the amplitude specified in Table 3 (depending on the specified random vibration severity level). In exceptional cases, such as when the test specimen is very sensitive to sinusoidal vibration, the relevant specification may specify a lower amplitude. 142
(m/s2)\/Hz
4.8-~19.2
6.2 Resonance check
Specified level
GB/T 2423. 11—1997
(0.05~0.2)
Sine amplitude
(peak value)
The relevant specification may require an initial and final resonance check. The frequency points at which mechanical resonance and other frequency-related effects (e.g., failures) occur during the initial and final resonance checks shall be recorded and compared during the inspection to provide additional information on the residual effects caused by the random vibration test. If any change in the resonant frequency occurs, the relevant specification shall state the measures taken. Unless otherwise specified in the relevant specification, the sine amplitude of 6.1 shall be used for the resonance check. 7 Initial test
The relevant specification shall specify the electrical and mechanical property tests required before the conditioning test. 8 Conditioning test
During the conditioning test, the test sample shall be subjected to the full level of random vibration. Unless otherwise specified in the relevant specification, the test sample shall be vibrated in three mutually perpendicular axes in sequence. The axes shall be selected so as to most easily expose the defects of the sample. Unless otherwise specified in the relevant specification, the sample shall be required to work during the conditioning test, if allowed, to determine the electrical properties and mechanical effects. For components, the relevant specification shall specify whether electrical and mechanical checks are to be carried out during the conditioning test and at which stage of the conditioning test these checks are to be carried out.
9 Final test
The relevant specification shall specify the electrical and mechanical performance tests required after the conditioning test. 10 Provisions to be made in the relevant specification
When the relevant specification includes this test, the following details shall be specified as applicable: a) Installation method of test sample (including magnetic interference, temperature and gravity effects, shock absorber characteristics and supplementary tests) (3.1); b) Reference points and control points (3.2);
c) Frequency range\ (4.1),
d) Acceleration spectral density level* (4.2); e) Conditioning test duration" (4.3); f) Reproducibility\ (5.2),
g) Total Vibration check (Chapter 6);
h) Upper limit of acceleration for frequency response measurement (Chapter 6);i) Initial test "(Chapter 7);
j) Functional test during conditional test" (Chapter 8);k) Final test\ (Chapter 9).
*Essential provisions.
Specified
Acceleration
Spectral densitybzxZ.net
(m/s*)2/Hz
Specified
Acceleration
Spectral density
GB/T 2423. 11-1997
Total RMS acceleration value
Total RMS acceleration for each acceleration spectral density per frequency range (rectangular spectrum, unit: m/s2) specified frequency range (~f)
5~1505~2001015010~20020~~15020~20020~5020-2 00020~5 00050~50050~2 00050~5 000Total RMS acceleration
Each frequency range for each—
Total RMS acceleration value
Total RMS acceleration of acceleration spectrum density (rectangular spectrum, unit: g) specified frequency range (J~f2)
5~1505~20010~15010~20020~15Q20~20d20~50020~2000|20-500050~50050~2000|50~5000Total RMS acceleration
0. 270. 31
Specified
Acceleration
Spectral density
GB/T2423.11—1997
Table 4b (end)
Specified frequency range (～)
5~1505~20Q10~15010~20020~15020~20020~50020~2 000|20-5 050~50050~2 0,50~5 000 Total RMS acceleration
GB/T2423.11-1997
Appendix A
(Informative Appendix)
Discussion on issues related to wideband random vibration testing The following points are discussed to provide users of this standard with background information on the selection of vibration test reproducibility and verification methods.
A1 Wideband random vibration, fixed narrowband random vibration and scanning random vibration tests We do not consider these three vibration test methods to be equivalent, so each test needs to be described separately. Wideband testing has priority and is also the most advanced method in terms of technology. A2 Test
The random vibration test method has been included in the national standard GB2423 (IEC68 standard) to expand the current sinusoidal vibration test GB/T2423.10 (IEC68-2-6). Random vibration testing is a method that is closer to the type of vibration that may exist in the actual environment, and the effects produced in the test sample are closer to the effects that may occur in use. When the actual environment is roughly random vibration, random vibration testing should be used as long as it is economically reasonable, because sinusoidal vibration and random vibration affect the failure mechanism of the sample in different ways. It has been pointed out in "Basic Principles of Testing" that in all national standards and IEC standard test methods, a certain degree of reproducibility is required when moving from one laboratory to another. Random vibration testing is no exception. To specify and conduct those random vibration tests, not only the actual environmental effects and appropriate reproducibility are required, but also a fast and simple test procedure. Unfortunately, there is no fast, simple and reproducible wide-band random vibration test under the current technical conditions. Simple tests are not reproducible tests, and reproducible tests are not simple tests. For some test applications, reproducibility is more important than simplicity. For other test applications, especially when the test cost is tight, simplicity is more important than reproducibility. A3 Reproducibility Level
Single test methods cannot meet the needs of the above various tests. Therefore, after comprehensive consideration, a variety of reproducibility levels are given, which are called high, medium and low reproducibility levels, and have different tolerance requirements. The reproducibility of vibration testing, when there are resonant components in the test sample, mainly depends on the vibration control of the input test sample. If high reproducibility is to be achieved, then highly selective (high Q) resonances require that the excitation of the test sample installation or fixing point be controlled within a very small bandwidth. For random vibration testing, this will result in narrowband analysis and band control of the acceleration spectrum density input to the test sample. Common test equipment can allow changes such as 30dB to 40dB of velocity spectrum density to be masked by the analyzer bandwidth. For example, a resonance of Q=40, including 10% of the total moving part mass (mass includes test sample, fixture and vibration table), will cause a 25dB change within 25Hz to 500Hz.
The sinusoidal vibration test given in GB/T2423.10 (IEC68-2-6) usually requires the amplitude to be kept within 15% (±1.2dB) at the control point. For the same reproducibility, a wide-band random vibration test requires the acceleration spectrum density to be controlled to approximately ±30% (±1.2dB), we believe that this level of reproducibility of random vibration test is difficult to achieve in practical applications. High reproducibility of wide-band random vibration test requires that the true value of acceleration spectrum density be controlled within ±3dB at the reference point. This is difficult to achieve for large and complex test samples, but it is relatively easy to achieve for test samples smaller than the vibration generator. For this reproducibility, the tolerance of the lateral acceleration spectrum density at the control point (not the reference point) and one or more selected control points in the predetermined direction must also be considered. These tolerances are wider than the reference point. For test samples larger than the mass of the vibration generator and fixture, the peak value of the lateral acceleration spectrum density is very large, and the frequency is different between two different test devices. Therefore, the lateral acceleration spectrum density level can exceed the acceleration spectrum density value specified in the predetermined direction, and 5dB is allowed.
GB/T 2423. 11-1997
The reproducibility requirement is to control the acceleration spectrum density to ±6dB at the reference point. Generally speaking, it is not very difficult to achieve this reproducibility for small test specimens, and it can be achieved with some care for large test specimens. Low reproducibility does not specify a tolerance for the true value of the acceleration spectral density. However, the analyzer indication value is required to be ±3dB. The recommended verification method given in the appendix of the low reproducibility test Fdc is designed to allow the use of a fundamental principle of vibration testing that is completely different from that of national standards and IEC environmental test methods. Generally speaking, the actual environment is represented by a specified severity level, and the reproducibility given by the test should be as high as the actual reproducibility of the same level. The basic principle of test Fdc is to allow high-Q resonances in the test specimen and fixture to correct the peaks and troughs of the acceleration spectral density spectrum. The peaks and troughs caused by the resonant components of the test specimen are often present during the actual service life, but their frequencies are generally different during the test. More severe troughs may occur in both the actual field and the laboratory. This principle is usually unacceptable because the test results are overly dependent on the fixture design and the size of the vibration table. The tolerances for this test are based on methods currently in use, but experience with the use of the test will indicate that the tolerances need to be revised in the future. A4 Verification Methods
The relevant specifications should state the level of reproducibility required for the actual test, and for low reproducibility, an equalization system or an analysis system may also be specified. Given these conditions, the test engineer is free to choose the verification method. The recommended verification methods are specified in the relevant annexes of tests Fda [GB/T2423.12 (IEC68-2-35) JFdb [GB/T2423.13 (IEC68-2-36)] and Fdc [GB/T2423.14 (IEC68-2-37) J. The verification methods in the appendix to Fda or Fdb are considered equivalent for the same level of reproducibility. For test sample-fixture systems whose transmissibility does not vary significantly with frequency, it is sufficient to check the transmissibility using a sine sweep and to check the flatness of the spectrum of the noise generator. This indirect method is given in Appendix C to Fda or Fdb. If an equalizer is connected to this system, then for high and medium reproducibility, this method requires a tighter tolerance of 4 dB to compensate for possible changes in the equalizer level, which will occur when the vibration level is increased from the adjusted value to the level specified in the test. A5 Estimation of verification error
Graphs based on many broadband practical filters are described [see Annex A of GB/T2423.12 (IEC68-2-35) (Test Fda) and GB/T2423.13 (IEC68-2-36) (Test Fdb) and are used to help estimate the so-called ripple. These graphs are suitable for the part of the spectrum in the peak-to-valley interference area caused by a vibrator with a single degree of freedom moving mass. As you know, the most important parameters are the peak-to-valley frequency and amplitude ratio, the filter bandwidth, and for analyzing errors, the most important parameter is the filter waveform internal element between the 12 dB and 3 dB attenuation points. A6 Scan speed and averaging time
When analyzing random processes, statistical averages are often used to represent data characteristics. For random vibration, the instrument must include time averaging. In order to obtain a reading of the acceleration spectral density with relatively small fluctuations, this time should be longer for the narrow bandwidths required for high and medium reproducibility. If a swept analysis is used, the time domain average will cause an unwanted frequency domain average. Therefore, the sweep speed should be slower with the upper limit associated with the averaging time.
A7 Measurement of total rms acceleration
In general, the acceleration spectral density is specified as a constant from low frequency f, to high frequency f?, with a certain minimum slope outside this range. However, when the tolerance is large, the total rms acceleration value must be strictly controlled. When the indirect verification method described in Chapter A4 above is used, if spectral analysis of the acceleration spectral density is not generally required, then the only quantity controlled at the final test time of the full level is the measurement of the rms acceleration.
A8 Future developments
The verification method described in the appendix to Tests Fda, Fdb and Fdc is based on the currently widely used method. Other verification methods of spectral density may also be used, such as digital analysis and real-time (time compressed) spectral analysis. These verification methods may be included in future revisions of the test methods once the instrumentation and data for these analyses become more widely available in vibration laboratories.13 (IEC68-2-36) (Test Fdb) Annex A, and is used to help estimate the so-called ripple tool. These diagrams are suitable for the spectrum of the part of the peak-to-valley interference area caused by the vibrator of the single-degree-of-freedom moving mass. As we all know, the most important parameters are the peak-to-valley frequency and amplitude ratio, the filter bandwidth, and for the analysis of errors, the most important parameter is the filter waveform element between the 12dB and 3dB attenuation points. A6 Scanning speed and averaging time
When analyzing random processes, statistical averages are often used to represent the data characteristics. For random vibration, the instrument must include time averaging. In order to obtain acceleration spectral density readings with relatively small fluctuations, this time should be long for the narrow bandwidth required for high and medium reproducibility. If a scanning analysis is used, the time domain average will cause unwanted frequency domain averages. Therefore, the scanning speed should be slowed down with the upper limit related to the averaging time.
A7 Measurement of total root mean square acceleration
In general, the acceleration spectral density is specified as a constant from low frequency f to high frequency f?, with a minimum slope outside this range. However, when the tolerances are larger, the total rms acceleration value must be strictly controlled. When the indirect verification method described in Chapter A4 above is used, if spectral analysis of the acceleration spectral density is not generally required, then the only quantity controlled at the final test time of the full level is the measurement of the rms acceleration.
A8 Future Developments
The verification methods described in the appendix to tests Fda, Fdb and Fdc are based on methods currently in widespread use. Other verification methods for spectral density may also be used, such as digital analysis and real-time (time compressed) spectral analysis. These verification methods may be included in future revisions of the test methods once the instrumentation and data for these analyses become more widely used in vibration laboratories. 1.1713 (IEC68-2-36) (Test Fdb) Annex A, and is used to help estimate the so-called ripple tool. These diagrams are suitable for the spectrum of the part of the peak-to-valley interference area caused by the vibrator of the single-degree-of-freedom moving mass. As we all know, the most important parameters are the peak-to-valley frequency and amplitude ratio, the filter bandwidth, and for the analysis of errors, the most important parameter is the filter waveform element between the 12dB and 3dB attenuation points. A6 Scanning speed and averaging time
When analyzing random processes, statistical averages are often used to represent the data characteristics. For random vibration, the instrument must include time averaging. In order to obtain acceleration spectral density readings with relatively small fluctuations, this time should be long for the narrow bandwidth required for high and medium reproducibility. If a scanning analysis is used, the time domain average will cause unwanted frequency domain averages. Therefore, the scanning speed should be slowed down with the upper limit related to the averaging time.
A7 Measurement of total root mean square acceleration
In general, the acceleration spectral density is specified as a constant from low frequency f to high frequency f?, with a minimum slope outside this range. However, when the tolerances are larger, the total rms acceleration value must be strictly controlled. When the indirect verification method described in Chapter A4 above is used, if spectral analysis of the acceleration spectral density is not generally required, then the only quantity controlled at the final test time of the full level is the measurement of the rms acceleration.
A8 Future Developments
The verification methods described in the appendix to tests Fda, Fdb and Fdc are based on methods currently in widespread use. Other verification methods for spectral density may also be used, such as digital analysis and real-time (time compressed) spectral analysis. These verification methods may be included in future revisions of the test methods once the instrumentation and data for these analyses become more widely used in vibration laboratories. 1.17
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