1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationEnvironmental testing Part 2-38: Tests Test Z/AD: Compositetemperature/humidity cyclic testBS EN 60068-2-38:2009National forewordThis British Standard is the UK implementation of
2、 EN 60068-2-38:2009. It isidentical to IEC 60068-2-38:2009. It supersedes BS EN 60068-2-38:1999which is withdrawn.The UK participation in its preparation was entrusted to Technical CommitteeGEL/104, Environmental conditions, classification and testing.A list of organizations represented on this comm
3、ittee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2010ISBN 978 0 580 52986 3ICS 19.040Compliance with a British Standard cannot confer immunity fromlegal obli
4、gations.This British Standard was published under the authority of the StandardsPolicy and Strategy Committee on 31 January 2010Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS EN 60068-2-38:2009EUROPEAN STANDARD EN 60068-2-38 NORME EUROPENNE EUROPISCHE NORM November
5、2009 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: Avenue Marnix 17, B - 1000 Brussels 2009 CENELEC - All rights of exploitation in any form and by any means reserv
6、ed worldwide for CENELEC members. Ref. No. EN 60068-2-38:2009 E ICS 19.040 Supersedes EN 60068-2-38:1999English version Environmental testing - Part 2-38: Tests - Test Z/AD: Composite temperature/humidity cyclic test (IEC 60068-2-38:2009) Essais denvironnement - Partie 2-38: Essais - Essai Z/AD: Ess
7、ai cyclique composite de temprature et dhumidit (CEI 60068-2-38:2009) Umgebungseinflsse - Teil 2-38: Prfverfahren - Prfung Z/AD: Zusammengesetzte Prfung, Temperatur/Feuchte, zyklisch (IEC 60068-2-38:2009) This European Standard was approved by CENELEC on 2009-09-01. CENELEC members are bound to comp
8、ly 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 Sec
9、retariat 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
10、 the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland,
11、 Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 60068-2-38:2009EN 60068-2-38:2009 - 2 - Foreword The text of document 104/482/FDIS, future edition 2 of IEC 60068-2-38, prepared by IEC TC 104, Environmental conditions, classification and methods of tes
12、t, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60068-2-38 on 2009-09-01. This European Standard supersedes EN 60068-2-38:1999. The major changes with regard to EN 60068-2-38:1999 concern the updating of the figures, changes to some of the wording and editorial co
13、rrections made for clarification. 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) 2010-06-01 latest date by which the national standards conflicting with the EN have to be wit
14、hdrawn (dow) 2012-09-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 60068-2-38:2009 was approved by CENELEC as a European Standard without any modification. _ BS EN 60068-2-38:2009- 3 - EN 60068-2-38:2009 Annex ZA (normative) Normative referenc
15、es 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 (incl
16、uding any amendments) applies. NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Year IEC 60068-1 -1)Environmental testing - Part 1: General and guidance EN 60068-119942)IEC 60068-2-30 -1)Env
17、ironmental testing - Part 2-30: Tests - Test Db: Damp heat, cyclic (12 h + 12 h cycle) EN 60068-2-30 20052)IEC 60068-2-78 -1)Environmental testing - Part 2-78: Tests - Test Cab: Damp heat, steady state EN 60068-2-78 20012)IEC Guide 104 -1)The preparation of safety publications and the use of basic s
18、afety publications and group safety publications - - 1)Undated reference. 2)Valid edition at date of issue. BS EN 60068-2-38:2009 2 60068-2-38 IEC:2009 CONTENTS 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 of test chamber 6
19、 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 of cold subcycle
20、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 specification .14 8 Informa
21、tion 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 BS EN 60068-2-38:200960068-2-38 IEC:2009 5 ENVIRONMENTAL TESTING Part 2-38: Tests Test Z/AD: Composite tem
22、perature/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 temperature/humidity and cold conditions. 2 Normative re
23、ferences 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 60068-1, Environmental testing Part
24、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 safety publications and the use of basic safety pub
25、lications 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. This test differs from other cyclic damp heat tests i
26、n 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 of excursions to sub-zero temperatures. The acceler
27、ated 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 to allow the penetration of a coherent mass of water
28、 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 for very small specimens but copious for large spec
29、imens. BS EN 60068-2-38:2009 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 characteristics of the specimens. 3.2 App
30、lication 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 characteristics are compatible with the r
31、ates 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 60068-2-78 is preferred for investi
32、gating 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 period, the degree of accelera
33、tion 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 loading should be such that the
34、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 f
35、or the physical and thermal characteristics of the test specimens and the types of failure mechanisms which are significant for each particular case. 4 Description of test chamber The exposure to moisture, followed by cold, can either be performed in one chamber or in two separate chambers. 4.1 Cham
36、ber for exposure to moisture The chamber for the exposure to moisture shall be so constructed that: a) The temperature can be varied between 25 C 2 K and 65 C 2 K in a period of between 1,5 h and 2,5 h for both rising and falling temperatures. b) The relative humidity can be maintained at (93 3) % d
37、uring the periods of constant or rising temperature and between 80 % RH and 96 % RH during the falling temperature periods. c) The conditions prevailing at any point in the working space are uniform and are as similar as possible to those prevailing in the immediate vicinity of suitably located temp
38、erature- and humidity-sensing devices. The air in the chamber shall therefore be continuously stirred at a rate necessary to maintain the specified conditions of temperature and humidity. d) The specimens under test shall not be subjected to radiant heat from the chamber conditioning processes. e) W
39、ater used for the maintenance of chamber humidity shall have a resistivity of not less than 500 m. f) Condensed water shall be continuously drained from the chamber and not used again unless it has been repurified. BS EN 60068-2-38:200960068-2-38 IEC:2009 7 Precautions shall be taken to ensure that
40、no condensed water from the walls and roof of the test chamber can fall on the specimens. 4.2 Chamber for exposure to cold The chamber for exposure to cold shall be so constructed that a) the temperature can be maintained at 10 C 2 K, b) the conditions prevailing at any point in the working space ar
41、e uniform and are as similar as possible to those prevailing in the immediate vicinity of suitably located temperature-sensing devices, The air in the chamber shall therefore be continuously moving. Care shall be taken that the thermal capacity of the specimen under test does not appreciably influen
42、ce conditions within the chamber. The humidity chamber may be used for exposure to cold, in which case it shall meet the requirements of 4.1 and, in addition, shall be so constructed that 1) the temperature can be lowered from 25 C 2 K to 10 C 2 K in a period of not more than 30 min, 2) the specimen
43、 can be held at a temperature of 10 C 2 K for a period of 3 h, 3) the temperature can be raised from 10 C 2 K to 25 C 2 K in a period of not more than 90 min. 5 Severities The number of 24 h cycles shall be 10, unless otherwise specified. If other than 10, the relevant specification shall define the
44、 number. 6 Testing procedure 6.1 Preconditioning (see Figure 1) Unless otherwise specified, the specimens in the unpacked, switched-off, ready-for-use state shall be subjected to the conditions for “assisted drying“ specified in IEC 60068-1 (55 C 2 K with a relative humidity not exceeding 20 %) for
45、a period of 24 h prior to the first cycle of the damp heat test. The specimens shall then be allowed to attain thermal stability at standard atmospheric conditions for testing, or as otherwise specified, before the initial measurements are made. BS EN 60068-2-38:2009 8 60068-2-38 IEC:2009 100 90 80
46、70 60 50 40 30 20 10 0 0 12 24 Time (h) Relative humidity not more than 20 % 60 57 53 50 40 30 20 10 0 0 12 24 Time (h) Relativehumidity(%)Temperature (C) Pre-conditioning period Drying period Stabilizing period Initial measurements No specific rate of cooling is required IEC 2241/08 Figure 1 Precon
47、ditioning 6.2 Initial measurements The specimens shall be visually inspected and electrically and mechanically checked as required by the relevant specification. 6.3 Conditioning The total temperature tolerance of 2 K given in this standard is intended to take account of absolute errors in the measu
48、rement, slow changes of temperature and temperature variations of the working space. However, in order to maintain the relative humidity within the required BS EN 60068-2-38:200960068-2-38 IEC:2009 9 tolerances, it is necessary to keep the temperature difference between any two points in the working
49、 space at any moment within narrower limits. The required humidity conditions will not be achieved if such temperature differences exceed 1 K. It may also be necessary to keep short-term fluctuations within 0,5 K to maintain the required humidity. The specimens shall be introduced into the humidity chamber, in the unpacked, switched-off, ready-for-use state, and mounted in the normal orientation, if this is known, or as otherwise specifie
