SIST EN 60068-2-80:2005

SLOVENSKI SIST EN 60068-2-80:2005

STANDARD
december 2005
Okoljski preskusi – 2-80. del: Preskusi – Preskus Fi: vibracije – mešani način
(IEC 60068-2-80:2005)
Environmental testing – Part 2-80: Tests – Test Fi: Vibration – Mixed mode (IEC
60068-2-80:2005)
ICS 19.040 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 60068-2-80
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2005
ICS 19.040; 29.020
English version
Environmental testing
Part 2-80: Tests –
Test Fi: Vibration –
Mixed mode
(IEC 60068-2-80:2005)
Essais d'environnement Umgebungseinflüsse
Partie 2-80: Essais – Teil 2-80: Prüfverfahren –
Essai Fi: Vibration - Mode mixte Prüfung Fi: Mixed-Mode Vibrationsprüfung
(CEI 60068-2-80:2005) (IEC 60068-2-80:2005)

This European Standard was approved by CENELEC on 2005-06-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60068-2-80:2005 E
Foreword
The text of document 104/363/FDIS, future edition 1 of IEC 60068-2-80, prepared by IEC TC 104,
Environmental conditions, classification and methods of test, was submitted to the IEC-CENELEC
parallel vote and was approved by CENELEC as EN 60068-2-80 on 2005-06-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-06-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60068-2-80:2005 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
ISO/IEC 17025 NOTE Harmonized as EN ISO/IEC 17025:2000 (not modified).
__________
- 3 - EN 60068-2-80:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60050-300 2001 International Electrotechnical Vocabulary - -
- Electrical and electronic measurements
and measuring instruments
Part 311: General terms relating to
measurements –
Part 312: General terms relating to
electrical measurements –
Part 313: Types of electrical measuring
instruments –
Part 314: Specific terms according to the
type of instrument
1)
IEC 60068-1 1988 Environmental testing EN 60068-1 1994
Part 1: General and guidance
IEC 60068-2-6 1995 Part 2: Tests - Test Fc: Vibration EN 60068-2-6 1995
+ corr. March 1995 (sinusoidal)

2)
IEC 60068-2-47 1999 Part 2-47: Test methods - Mounting of EN 60068-2-47 1999
components, equipment and other articles
for vibration, impact and similar dynamic
tests
IEC 60068-2-64 1993 Part 2: Test methods - Test Fh: Vibration, EN 60068-2-64 1994
+ corr. October 1993 broad-band random (digital control) and
guidance
IEC 60068-3-8 2003 Part 3-8: Supporting documentation and EN 60068-3-8 2003
guidance - Selecting amongst vibration
tests
IEC 60068-5-2 1990 Part 5: Guide to drafting of test methods - EN 60068-5-2 1999
Terms and definitions
ISO 2041 1990 Vibration and shock - Vocabulary - -

1)
EN 60068-1 includes corrigendum 1988 + A1:1992 to IEC 60068-1.
2)
EN 60068-2-47:1999 is superseded by EN 60068-2-47:2005, which is based on IEC 60068-2-47:2005.

NORME CEI
INTERNATIONALE
IEC
60068-2-80
INTERNATIONAL
Première édition
STANDARD
First edition
2005-05
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Essais d’environnement –
Partie 2-80:
Essais – Essai Fi: Vibration – Mode mixte

Environmental testing –
Part 2-80:
Tests – Test Fi: Vibration – Mixed mode

CODE PRIX
X
Commission Electrotechnique Internationale
PRICE CODE
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

60068-2-80  IEC:2005 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11

1 Scope.13
2 Normative references .13
3 Terms and definitions .15
4 Requirements for testing .25
4.1 General .25
4.2 Control systems .25
4.3 Basic motion .25
4.4 Cross axis motion.25
4.5 Mounting .27
4.6 Measuring systems.27
5 Requirements for testing mixed mode.29
5.1 Vibration tolerances – Random.31
5.2 Vibration tolerances – Sine.37
5.3 Control strategy.39
5.4 Vibration response investigation.41
6 Severities .41
6.1 Broadband random vibration.43
6.2 Random narrowbands .43
6.3 Sine tones .45
7 Preconditioning .47
8 Initial measurements .47
9 Testing .47
9.1 General .47
9.2 Initial vibration response investigation .49
9.3 Low-level excitation for equalization prior to testing.51
9.4 Mixed mode testing .51
9.5 Final vibration response investigation.53
10 Intermediate measurements .53
11 Recovery.53
12 Final measurements .53
13 Information to be given in the relevant specification .53
14 Information to be given in the test report .55

Annex A (informative) Mixed mode general information.59
Annex B (informative) Guidance.71

Bibliography.83

60068-2-80  IEC:2005 – 5 –
Figure 1 – Boundaries for acceleration spectral density (see also 5.1.1) .29
Figure 2 – Stochastical excitation, representation of signal clipping and Gaussian
(normal) probability.31
Figure 3 – Statistical accuracy of acceleration spectral density versus degrees of
freedom for different confidence levels .33
Figure 4 – Distribution (probability density) of sine, sine-on-random and random signals .35
Figure 5 – Recommended sinusoidal sweep rate as a function of power ratio for sine
on random depending on E .47
sor
Figure A.1 – Sine at 160 Hz .63
Figure A.2 – Sine at 380 Hz .65
Figure A.3 – Auto correlation – Sine at 160 Hz .65

Table A.1 – Determination of sine wave with APD calculation .67
Table A.2 – Determination of sine wave with autocorrelation calculation .69

60068-2-80 © IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-80: Tests – Test Fi: Vibration – Mixed mode

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60068-2-80 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
The text of this standard is based on the following documents:
FDIS Report on voting
104/363/FDIS 104/368/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
It has the status of a basic safety publication in accordance with IEC Guide 104.

60068-2-80  IEC:2005 – 9 –
This standard forms Part 2-80 of IEC 60068 which consists of the following major parts, under
the general title Environmental testing:
Part 1: General and guidance
Part 2: Tests
Part 3: Supporting documentation and guidance
Part 4: Information for specification writers
Part 5: Guide to drafting of test methods
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
60068-2-80  IEC:2005 – 11 –
INTRODUCTION
This method for mixed mode vibration testing requires the digital control of broadband random
vibrations and techniques associated with the combination of sinusoidal vibration and/or
specified narrowband random with a broadband random background.
This standard is intended for general application to components, equipment and other
products, hereinafter referred to as ”specimens”, when simulation is required of broadband
responses of a complex nature for the specimens.
The test method is based primarily on the use of an electrodynamic or a servo-hydraulic
vibration generator with an associated computer based control system used as a vibration
testing system.
It is emphasized that mixed mode testing always demands a certain degree of engineering
judgement and both supplier and purchaser should be fully aware of this fact. The writer
of the relevant specification is expected to select the testing procedure and the values of
severity appropriate to the specimen and its use.

60068-2-80  IEC:2005 – 13 –
ENVIRONMENTAL TESTING –
Part 2-80: Tests – Test Fi: Vibration – Mixed mode

1 Scope
This part of IEC 60068 is intended for general application for testing specimens when
simulation is required of vibration excitation of a complex and mixed nature.
The purpose of the test is to demonstrate the adequacy of the specimen to resist the specified
mixed mode excitation without unacceptable degradation of its functional and/or structural
performance. It is particularly useful for tailoring mixed mode environments where measured
data are available for the real life environment.
The test also helps reveal the accumulated effects of stress induced by random vibration,
mixed with sine and/or random, and the resulting mechanical weakness and degradation in
specified performances, and to use this information, in conjunction with the relevant
specification, to assess the acceptability of specimens. In some cases, this standard may also
be used to demonstrate the mechanical robustness of specimens.
This standard is applicable to specimens which may be subjected to vibration of a random
and/or a combination of random and deterministic nature resulting from transportation or real
life environments, for example in aircraft, space vehicles and for items in their transportation
container when the latter may be considered as part of the specimen itself.
Although primarily intended for electrotechnical specimens, this standard is not restricted to
such specimens and may be used in other fields where desired.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050(300):2001, International Electrotechnical Vocabulary (IEV) – Electrical and
electronic measurements and measuring instruments –
Part 311: General terms relating to measurements
Part 312: General terms relating to electrical measurements
Part 313: Types of electrical measuring instruments
Part 314: Specific terms according to the type of instrument
IEC 60068-1:1988, Environmental testing – Part 1: General and guidance
IEC 60068-2-6:1995, Environmental testing – Part 2-6: Tests -Test Fc: Vibration (sinusoidal)
IEC 60068-2-47:1999, Environmental testing – Part 2-47: Test methods – Mounting of
components, equipment and other articles for vibration, impact and similar dynamic tests

60068-2-80  IEC:2005 – 15 –
IEC 60068-2-64:1993, Environmental testing – Part 2-64: Test methods – Test Fh: Vibration,
broadband random (digital control) and guidance
IEC 60068-3-8:2003, Environmental testing – Part 3-8: Supporting documentation and
guidance – Selecting amongst vibration tests
IEC 60068-5-2:1990, Environmental testing – Part 5-2: Guide to drafting of test methods –
Terms and definitions
ISO 2041:1990, Vibration and shock – Vocabulary
3 Terms and definitions
For the purposes of this document, the following terms and definitions are generally defined in
ISO 2041, IEC 60050(300), IEC 60068-1, IEC 60068-2-6, IEC 60068-2-64 and IEC 60068-5-2.
Where, for the convenience of the reader, a definition from one of those sources is included
here, the derivation is indicated and departures from the definitions in those sources are also
indicated.
The additional terms and definitions that follow are also applicable.
3.1
cross axis motion
motion not in the direction of the external stimulus, generally specified in the two orthogonal
axes
3.2
actual motion
motion represented by the wideband signal returned from the reference point transducer
3.3
fixing point
part of the specimen in contact with the fixture or vibration table at a point where the
specimen is normally fastened in service
NOTE If a part of the real mounting structure is used as the fixture, the fixing points are taken as those of the
mounting structure and not of the specimen.
3.4
control point
3.4.1
single point control
control method using the signal from the transducer at the reference point in order to maintain
this point at the specified vibration level
3.4.2
multipoint control
control method using the signals from each of the transducers at the check points. The
signals are either continuously averaged arithmetically or processed by using comparison
techniques, depending upon the relevant specification, see also 3.9
3.5
g
n
standard acceleration due to the earth's gravity, which itself varies with altitude and geo-
graphical latitude
NOTE For the purposes of this standard, the value of g is rounded up to the nearest whole number, i.e. 10 m/s .
n
60068-2-80  IEC:2005 – 17 –
3.6
measuring points
specific points at which data are gathered for conducting the test. These points are of three
types, as defined below
3.6.1
check point
point located on the fixture, on the vibration table or on the specimen as close as possible to
one of its fixing points, and in any case rigidly connected to it
NOTE 1 A number of check points are used as a means of ensuring that the test requirements are satisfied.
NOTE 2 If four or fewer fixing points exist, each is used as a check point. If more than four fixing points exist, four
representative fixing points will be defined in the relevant specification to be used as check points.
NOTE 3 In special cases, for example for large or complex specimens, the check points will be prescribed by the
relevant specification if not close to the fixing points.
NOTE 4 Where a large number of small specimens are mounted on one fixture, or in the case of a small specimen
where there are a number of fixing points, a single check point (that is the reference point) may be selected for the
derivation of the control signal. This signal is then related to the fixture rather than to the fixing points of
the specimen(s). This procedure is only valid when the lowest resonance frequency of the loaded fixture is well
above the upper frequency of the test.
3.6.2
reference point
point, chosen from the check points, signal of which is used to control the test, such that the
requirements of this standard are satisfied
3.6.3
fictitious reference point
point derived from multiple check points either manually or automatically, the result of which
is used to control the test, so that the requirements of this standard are satisfied
3.6.4
response points
specific points on the specimen from which data is gathered for the purpose of the vibration
response investigation
NOTE These points are not check or reference points
3.7
preferred testing axes
three orthogonal axes that correspond to the most vulnerable axes of the specimen
3.8
sampling frequency
number of discrete magnitude values taken per second to record or represent a time-history in
a digital form
3.9
multipoint control strategies
method for calculating the reference control signal when using multipoint control. The
following frequency domain control strategies are available, see also 3.4.2
3.9.1
averaging
process of determining the control value as the arithmetic average of the signal value, see
also 3.31, of each frequency at more than one check point

60068-2-80  IEC:2005 – 19 –
3.9.2
extremal
process of determining the control value as the maximum or minimum of the signal value, see
also 3.31, of each frequency from each check point
3.10
MAX/SUM
random-on-random severities in order to define the ASD (see 3.14) value of the narrow bands
NOTE MAX means the maximum of either the background or narrow band ASD values, SUM means adding the
two ASD values.
3.11
crest factor
ratio of the peak value to the r.m.s. value of the complex mixed-mode waveform
[ISO 2041]
3.12
super positional strategy
strategy which defines the method for calculating the reference acceleration spectral density
at each frequency line from the sine tones and the random ASD
3.13
–3 dB bandwidth
B
frequency bandwidth between two points in a frequency response function which is 0,708 of
the maximum response when associated with a single resonance peak
3.14
acceleration spectral density
ASD
mean-square value of that part of an acceleration signal passed by a narrowband filter of a
centre frequency, per unit bandwidth, to the extent that the bandwidth approaches zero and
the averaging time approaches infinity
3.15
bias error
for the random signal, systematic error in the estimate of the acceleration spectral density due
to the finite frequency resolution used in practice. For the sinusoidal signal, systematic error
in the estimate of the amplitude of the sinusoidal component within the mixed mode signal
due to the averaging time
3.16
control acceleration spectral density
acceleration spectral density measured at the reference point or the fictitious point
3.17
control system loop
sum of the following actions:
– digitizing the analogue mixed mode waveform of the signal derived from the reference
point;
– performing the necessary processing;
– producing an updated analogue mixed mode drive waveform to the vibration system power
amplifier (see also Clause B.1)

60068-2-80  IEC:2005 – 21 –
3.18
drive signal clipping
limitation of the maximum value of the drive signal, expressed as a crest factor
3.19
effective frequency range (see also Figure 1)
range from the actual frequency below f to the actual frequency above f due to initial and
1 2
final slopes
3.20
error acceleration spectral density
difference between the specified acceleration spectral density and the control acceleration
spectral density
3.21
equalization
minimization of the error acceleration spectral density
3.22
final slope (see also Figure 1)
part of the specified acceleration spectral density above f
3.23
frequency resolution
width of the frequency intervals in the acceleration spectral density in hertz
NOTE It is equal to the reciprocal of the length of each of the samples into which the record is partitioned in order
to calculate the indicated acceleration spectral density in digital analysis. The number of frequency lines is equal to
the number of intervals in a given frequency range.
3.24
indicated acceleration spectral density
estimate of the true acceleration spectral density read from the analyser presentation
corrupted by the instrument error, the random error and the bias error
3.25
initial slope (see also Figure 1)
part of the specified acceleration spectral density below f
3.26
instrument error
error associated with each analogue item of the input to the control system and control
system analogue items
3.27
random error
error changing from one estimate to another of the acceleration spectral density because of
the limitation of averaging time and filter bandwidth in practice
3.28
record
collection of equally spaced data points in the time domain that are used in the calculation of
the Fast Fourier Transform
60068-2-80  IEC:2005 – 23 –
3.29
reproducibility
the closeness of the agreement between the results of measurements of the same value of
the same quantity where the individual measurements are made
– by different methods,
– with different measuring instruments,
– by different observers,
– in different laboratories,
– after intervals of time which are long compared with the duration of a single measurement,
– under different customary conditions of use of the instruments employed.
NOTE The term “reproducible” also applies to the case where only certain of the preceding conditions are taken
into account.
[IEC 60050(300)]
3.30
root-mean-square value
and f
the root-mean-square value (r.m.s. value) of a flat spectrum over an interval between f
1 2
(see Figure 1), is the square root of the average of the squared values of the function over the
interval
NOTE In this test method, the r.m.s. values of acceleration, velocity and displacement can be calculated for the
random content only or for the mixed mode Sine on Random (SoR) and Random on Random (RoR), see B.2.4.
3.31
signal value
for the random component of the mixed mode signal, it refers to the acceleration spectral
density value and for the sinusoidal component of the mixed mode signal, it refers to the
amplitude value
3.32
standard deviation
σ
in vibration theory, the mean value of vibration is equal to zero. Therefore for a random time
history, the standard deviation is equal to the r.m.s. value
3.33
statistical accuracy
ratio of true acceleration spectral density to indicated acceleration spectral density
NOTE Refers to the random portion only of the mixed mode signal.
3.34
statistical degrees of freedom
for estimation of acceleration spectral density of random data with a time-averaging
technique, the effective number of statistical degrees of freedom is derived from the
frequency resolution and the effective averaging time
3.35
sweep cycle
traverse of the specified frequency range once in each direction, for example 5 Hz to 500 Hz
to 5 Hz
NOTE In contrast to ‘sweep cycle’ one sweep denotes a sweep in one direction only, either up or down.
[IEC 60068-2-6]
60068-2-80  IEC:2005 – 25 –
3.36
sweep rate
rate at which the sinusoidal frequency is varied, either in octaves per minute or hertz per
second
3.37
true acceleration spectral density
acceleration spectral density of the random waveform acting on the specimen
4 Requirements for testing
4.1 General
The characteristics apply to the complete vibration testing system, which for an electro-
dynamic and a servo-hydraulic testing system includes the power amplifier, vibrator and
loaded test fixture and control system.
The basic and cross axis motions described below shall be checked either before starting the
test or during testing by using an additional input monitor channel of the controller. The
relevant specification shall state the investigation test levels and procedures to be used.
The standardized test method consists of the following test sequence and shall be applied in
each of the mutually perpendicular axes of the test specimen:
a) An initial vibration response investigation, with low level sinusoidal or random excitation,
see also 5.4 and 9.2.
b) The mixed mode excitation as the load or stress test.
c) A final vibration response investigation (see also 9.5) to compare the results with the
initial one and to detect possible mechanical failures due to a change of the dynamic
behaviour.
However, the relevant specification may renounce the requirement for a response
investigation, or part thereof, if the dynamic behaviour of the test specimen is known or not of
interest.
4.2 Control systems
Special software control packages are required for the control system which have the
capability of analysing and controlling tests where a mixture of random on random or sine on
random excitations/specifications is required.
4.3 Basic motion
The basic motion of the fixing points of the specimen, which shall be prescribed by the
relevant specification and have substantially identical motions, shall be rectilinear. If sub-
stantially identical motions are difficult to achieve, then multipoint control shall be used.
The characteristics of the basic motion shall be nominally a Gaussian distribution for the
random waveform and sinusoidal for the periodic components.
4.4 Cross axis motion
Cross axis motion should be checked either before the test is applied by conducting a sine or
random investigation at a level prescribed by the relevant specification or during testing by
utilizing an additional monitoring channel.

60068-2-80  IEC:2005 – 27 –
The signal value of each frequency at the check points in any axis perpendicular to the
specified axis shall not exceed the specified signal values above 500 Hz and below 500 Hz
shall not exceed –3 dB of the specified signal values. The total r.m.s. acceleration in any axis
perpendicular to the specified axis shall not exceed 50 % of the r.m.s. value for the specified
axis. For example for a small specimen, the signal value of the permissible cross motion may
be limited such that it does not exceed –3 dB of the basic motion, if so prescribed by the
relevant specification.
At some frequencies or with large-size or high-mass specimens it may be difficult to achieve
these. Also in those cases where the relevant specification requires severities with a large
dynamic range it may also be difficult to achieve these. In such cases the relevant
specification shall state which of the following requirements applies:
a) cross axis motion in excess of that specified above shall be monitored and stated in the
test report;
b) cross axis motion need not be monitored.
4.5 Mounting
The specimen shall be mounted in accordance with IEC 60068-2-47. In any case, the
transmissibility curve chosen from IEC 60068-2-47 shall be squared before multiplication with
the ASD spectrum or multiplied direct for the sine amplitudes.
4.6 Measuring systems
The characteristics of the measuring system shall be such that it can be determined that the
true value of the vibration as measured in the intended axis at the reference point is within the
tolerance required for the test.
The frequency response of the overall measuring system, which includes the transducer, the
signal conditioner and the data acquisition and processing device, has a significant effect on
the accuracy of the measurements. The frequency range of the measuring system shall
extend from at least 0,5 times the lowest frequency (f ) to 2,0 times the highest frequency (f )
1 2
of the test frequency range, see also Figure 1. The frequency response of the measuring
system shall be flat within ±5 % in this frequency range.

60068-2-80  IEC:2005 – 29 –
+3
–3
0,5 f f f 2f
1 1 2 2
Frequency  Hz
IEC  627/05
Figure 1 – Boundaries for acceleration spectral density
(see also 5.1.1)
5 Requirements for testing mixed mode
This standard provides test methods for applying random vibration in combination with either
narrow band random, sinusoidal vibration, or both. The narrow band random and the
sinusoidal components may be swept over a defined frequency range as defined in the
relevant specification. Mixed mode testing shall take into account the following.
The relevant specification shall state whether the narrow band random profiles are the
maximum (MAX) spectral levels or shall be added to the background spectral profile (SUM).
The acceleration spectrum can either be
a) a super positional acceleration spectrum of the broadband random, the narrow band
random and the sine tones for control systems where the sine wave is generated at the
Fourier spectral lines,
or
b) a super positional acceleration spectrum of the broadband random and the narrow band
random with an independent sine tones, that is for control systems where the sine wave is
generated continuously in the frequency domain.
Acceleration spectral density  dB

60068-2-80  IEC:2005 – 31 –
5.1 Vibration tolerances – Random
5.1.1 Check and reference points
The indicated acceleration spectral density in the required axis at the reference point and
check points between f and f in Figure 1 shall be within ±3 dB allowing for the instrument
1 2
error, referred to the specified acceleration spectral density. The random error and the bias
error are not included in the tolerances. The random error can be calculated.
The r.m.s. value of acceleration, computed or measured, between f and f , shall be within
1 2
±10 % of the r.m.s. value associated with the specified acceleration spectral density. These
values are valid for both the reference point and fictitious reference point.
At some frequencies or with large-size or high-mass specimens, it may be difficult to achieve
these values. In such cases it is expected that the relevant specification will prescribe a wider
tolerance.
The initial slope shall be not less than +6 dB/octave and the final slope shall be
–24 dB/octave or steeper (see also B.2.3).
For swept narrow band random tests the tolerances on the swept components of the test
specification shall be the same as for the wide band component. However, at some sweep
rates, these tolerances may not be achievable. Therefore, the tolerance requirements for
these components shall be stated in the relevant specification.
5.1.2 Distribution
The instantaneous acceleration values at the reference point shall have an approximately
normal (Gaussian) distribution as given in Figure 2. A validation shall be performed during
normal system calibration. For mixed mode signals, with sine waves, see Figure 4.

Peak value 3σ
2σ
σ
r.m.s value
Probability
Time
σ
2σ
Peak value
3σ
IEC  628/05
Figure 2 – Stochastical excitation, representation of signal clipping
and Gaussian (normal) probability
The drive signal clipping shall have a value of at least 2,5 (see also 3.18). The crest factor of
the acceleration waveform at the reference point shall be examined to ensure that the signal
contains peaks of at least 3 times the specified r.m.s value, unless otherwise prescribed by
the relevant specification.
60068-2-80  IEC:2005 – 33 –
If a fictitious reference point is used for control, the requirement for the crest factor applies to
all the check points used to form the control acceleration spectral density.
The probability density function shall be computed for the reference point for a duration of
2 min at the beginning, middle and end of the test duration.
5.1.3 Statistical accuracy
The statistical accuracy is determined from the statistical degrees of freedom N and the
d
confidence level (see also Figure 3). The statistical degrees of freedom are given by:
N =2B × T (1)
d e a
where
B is the frequency resolution;
e
T is the effective averaging time;
a
N shall not be less than 120, unless otherwise specified by the relevant specification.
d
If the relevant specification states confidence levels to be met during the test, Figure 3 should
be used to calculate statistical accuracy.

dB %
99 %
Confidence levels
95 %
90 %
50 %
50 %
–1
90 %
–2
95 %
99 %
–3
–4 40
30 40 50 60 70 80 90 100 120 200 300 400 500
Statistical degrees of freedom
IEC  629/05
Figure 3 – Statistical accuracy of acceleration spectral density versus degrees of
freedom for different confidence levels

Statistical accuracy
60068-2-80  IEC:2005 – 35 –
2 2
Sine 120 Hz, 50 m/s + Random 20.200 Hz , different ASD values  (overall rms in m/s )
0,010
Pure Sine
0,009
2 3
Pure Sine
0,1 m /s
0,008
2 3
1 m /s
0,007 2 3
5 m /s
2 3
0,006
5 m /s pure Random
Pure Random
0,005
0,004
0,003
0,002
0,001
0,000
–150 –100 –50 0 50 100 150
Control acceleration  m/s
IEC  630/05
Figure 4 – Distribution (probability density) of sine, sine-on-random
and random signals
5.1.4 Frequency resolution
The frequency resolution B Hz necessary to minimize the difference between the true and
e
the indicated acceleration spectral density shall be selected by taking the digital controller
frequency range divided by the number of spectral lines (n).
B = f /n (2)
e high
where
f is the frequency range of the digital vibration controller in hertz and should be
high
greater than 2f , that is f ≥ 2f , see Figure 1;
2 high 2
n number of spectral lines equally spread over the frequency bandwidth to f .
high
The frequency resolution shall be given in the relevant specification, (see also Clause 13,
item h).
5.1.4.1 Random on random
B shall be chosen such that:
e
– as a minimum a frequency line coincides with the frequency f in Figure 1 and the first
frequency line is at 0,5 of f ;
– also that two frequency lines define the initial slope of the first sweeping narrowband.
Probability density
60068-2-80  IEC:2005 – 37 –
If this gives two different values then the smallest B shall be chosen.
e
NOTE There is a compromise between having a finer B , resulting in a slower loop control time and better
e
definition of the RoR spectrum. Also faster sweep rates for the sweeping bands may require a greater frequency
resolution in order to maintain control over the sweeping bandwidths.
5.1.4.2 Sine on random
B shall be chosen such that:
e
as a minimum, a frequency line coincides with the frequency f in Figure 1 and the first
frequency line is at 0,5 of f .
The sine sweep should where possible be continuous. For control systems where the sine
wave generation jumps from one frequency line to the next, B should be less than 0,1 %
e
f .
high
5.2 Vibration tolerances – Sine
5.2.1 Reference point
For swept sine on random testing, a digital tracking filter is normally employed to estimate the
sinusoidal amplitude. A tracking filter will also reduce the random portion of the signal.
However, the estimated value of the sinusoidal amplitude includes contributions from the
random portion of the signal around sinusoidal frequency. Also, the larger the ratio of random
signal ASD value to the square value of the sinusoidal r.m.s., hereinafter referred to as the
“power ratio”, the greater will be the random error produced. A reduction in the bandwidth of
the tracking filter will make the random error smaller. However, a narrower bandwidth for the
tracking filter requires a larger number of averages.
When the specimen has sharp, high quality resonances, using a larger number of averages
produces a larger bias error. The bias error is the difference between the averaged sine
amplitude and the true response.
Vibration tolerances for the sine tones in swept sine on random testing shall be larger than
the combined error of the random er
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