1、 IEC 60068-2-38Edition 2.0 2009-01INTERNATIONAL STANDARD NORME INTERNATIONALEEnvironmental testing Part 2-38: Tests Test Z/AD: Composite temperature/humidity cyclic test Essais denvironnement Partie 2-38: Essais Essai Z/AD: Essai cyclique composite de temprature et dhumidit IEC60068-2-38:2009 BASIC
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16、us avez des questions, visitez le FAQ du Service clients ou contactez-nous: Email: csciec.ch Tl.: +41 22 919 02 11 Fax: +41 22 919 03 00 IEC 60068-2-38Edition 2.0 2009-01INTERNATIONAL STANDARD NORME INTERNATIONALEEnvironmental testing Part 2-38: Tests Test Z/AD: Composite temperature/humidity cyclic
17、 test Essais denvironnement Partie 2-38: Essais Essai Z/AD: Essai cyclique composite de temprature et dhumidit INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE NICS 19.040 PRICE CODECODE PRIXISBN 2-8318-1022-6BASIC SAFETY PUBLICATION PUBLICATION FONDAMENTALE DE SC
18、URIT Registered trademark of the International Electrotechnical Commission Marque dpose de la Commission Electrotechnique Internationale 2 60068-2-38 IEC:2009 CONTENTS FOREWORD.3 1 Scope.5 2 Normative references .5 3 General 5 3.1 Description of the test .5 3.2 Application of the test6 4 Description
19、 of test chamber 6 4.1 Chamber for exposure to moisture.6 4.2 Chamber for exposure to cold7 5 Severities .7 6 Testing procedure 7 6.1 Preconditioning (see figure 1)7 6.2 Initial measurements .8 6.3 Conditioning 8 6.4 Test cycle12 6.4.1 Description of temperature/humidity subcycle12 6.4.2 Description
20、 of cold subcycle 12 6.4.3 Description of 24 h cycles with no exposure to cold .13 6.4.4 Description of final cycle13 6.5 Final measurements 13 6.5.1 At high humidity.13 6.5.2 Immediately upon removal from the chamber.13 6.5.3 After final drying 13 7 Information to be given in the relevant specifica
21、tion .14 8 Information to be given in the test report 14 Figure 1 Preconditioning 8 Figure 2 Exposure to humidity followed by exposure to cold 10 Figure 3 Exposure to humidity not followed by exposure to cold.11 60068-2-38 IEC:2009 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ ENVIRONMENTAL TESTING
22、Part 2-38: Tests Test Z/AD: Composite temperature/humidity cyclic test 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 intern
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30、 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
31、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
32、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 60068-2-38 has been prepared by IEC technical committee 104: Environmental conditions, classification and methods of test. This second edit
33、ion cancels and replaces the first edition, published in 1974, and constitutes a technical revision. The major changes with regard to the previous edition concern the updating of the figures, changes to some of the wording and editorial corrections made for clarification. The text of this standard i
34、s based on the following documents: FDIS Report on voting 104/482/FDIS 104/487/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. 4 60068-2-38 IEC:2009 This publication has been drafted in accordance with the ISO/IE
35、C Directives, Part 2. It has the status of a basic safety publication in accordance with IEC Guide 104. A list of all the parts in the IEC 60068 series, under the general title Environmental testing, can be found on the IEC website. The committee has decided that the contents of this publication wil
36、l remain unchanged until the maintenance result dateindicated 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. 60068-2-38 IEC:2009 5 ENVIRONMENTA
37、L TESTING Part 2-38: Tests Test Z/AD: Composite temperature/humidity cyclic test 1 Scope IEC 60068-2-38 provides a composite test procedure, primarily intended for component type specimens, to determine, in an accelerated manner, the resistance of specimens to the deteriorative effects of high tempe
38、rature/humidity and cold conditions. 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
39、) applies. IEC 60068-1, Environmental testing Part 1: General and guidance IEC 60068-2-30, Environmental testing Part 2-30: Tests Test Db: Damp heat, cyclic (12 h + 12 h cycle) IEC 60068-2-78, Environmental testing Part 2-78: Tests Test Cab: Damp heat, steady state IEC Guide 104, The preparation of
40、safety publications and the use of basic safety publications and group safety publications 3 General 3.1 Description of the test Test Z/AD is a cyclic temperature/humidity test which is designed to reveal defects in test specimens caused by “breathing“ as distinct from the absorption of moisture. Th
41、is test differs from other cyclic damp heat tests in that it derives its increased severity from: a) a greater number of temperature variations or “pumping“ actions in a given time; b) a greater cyclic temperature range; c) a higher cyclic rate of change of temperature; d) the inclusion of a number
42、of excursions to sub-zero temperatures. The accelerated breathing and the effect of the freezing of trapped water in cracks and fissures are the essential features of this composite test. It is emphasized, however, that the freezing effect will occur only if the fissure dimensions are large enough t
43、o allow the penetration of a coherent mass of water as is normally the case in fissures between seals and metal assemblies, or between seals and wire terminations. The degree of condensation will depend mainly upon the thermal time constant of the surface of the test specimens and may be negligible
44、for very small specimens but copious for large specimens. 6 60068-2-38 IEC:2009 Similarly, the breathing effect will be more apparent on specimens which contain relatively large air-filled or gas-filled voids, but again, the severity of the test will depend to some extent on the thermal characterist
45、ics of the specimens. 3.2 Application of the test For the reasons given above, it is recommended that this test procedure be limited to component type specimens when the construction of the specimens suggests a “breathing“ type of damp heat test combined with icing and where the thermal characterist
46、ics are compatible with the rates of change of temperature, etc. of test Z/AD. For solid type specimens, e.g. plastic encapsulated, where there may be small hairline cracks or porous material, the absorption or diffusion mechanisms will predominate and a steady damp heat such as test C of IEC 60068-
47、2-78 is preferred for investigating these effects. For larger specimens such as equipment or when it is essential for components to ensure thermal stability during the various phases of the cycle, test Db of IEC 60068-2-30 should be employed, although due to the reduced number of cycles in a given p
48、eriod, the degree of acceleration may not be as fast. In this case, test Db should normally form part of a sequence such as that defined in IEC 60068-1. As in other damp heat tests, a polarizing voltage or electrical loading may be applied to the specimens. In the case of electrical loading, the loa
49、ding should be such that the temperature rise of the specimens does not unduly affect the chamber conditions. From the above, test Z/AD should not be considered to be interchangeable with, or an alternative to, either steady-state or other cyclic damp heat tests, but the choice of test procedure should be made with due regard for the physical and thermal characteristics of the test specimens and the t
