1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsWB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1Environmental testing Part 2-14: Tests Test N: Change of temperatureBS EN 60068-2-14:2009National forewordThis Br
2、itish Standard is the UK implementation of EN 60068-2-14:2009. It isidentical to IEC 60068-2-14:2009. It supersedes BS EN 60068-2-14:2000 andBS EN 60068-2-33:2000, which are withdrawn.The UK participation in its preparation was entrusted to Technical CommitteeGEL/104, Environmental conditions, class
3、ification and testing.A list of organizations represented on this committee 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 2009ISBN 978 0 580 52985 6ICS 19.040Co
4、mpliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of the StandardsPolicy and Strategy Committee on 30 September 2009Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS EN 60068-2-14:2009E
5、UROPEAN STANDARD EN 60068-2-14 NORME EUROPENNE EUROPISCHE NORM July 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 CENE
6、LEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 60068-2-14:2009 E ICS 19.040 Supersedes EN 60068-2-14:1999 and EN 60068-2-33:1999English version Environmental testing - Part 2-14: Tests - Test N: Change of temperature (IEC 60068-2-14:
7、2009) Essais denvironnement - Partie 2-14: Essais - Essai N: Variation de temprature (CEI 60068-2-14:2009) Umgebungseinflsse - Teil 2-14: Prfverfahren - Prfung N: Temperaturwechsel (IEC 60068-2-14:2009) This European Standard was approved by CENELEC on 2009-07-01. CENELEC members are bound to comply
8、 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 Secre
9、tariat 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 t
10、he 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, P
11、ortugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 60068-2-14:2009EN 60068-2-14:2009 - 2 - Foreword The text of document 104/481/FDIS, future edition 6 of IEC 60068-2-14, prepared by IEC TC 104, Environmental conditions, classification and methods of test,
12、 was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60068-2-14 on 2009-07-01. This European Standard supersedes EN 60068-2-14:1999 and EN 60068-2-33:1999. The major changes with regard to EN 60068-2-14:1999 concern: merging of EN 60068-2-14:1999 and EN 60068-2-33:1999:
13、Guidance on change of temperature tests; updating of the figures, changes to some of the wording and editorial corrections 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 b
14、y endorsement (dop) 2010-04-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2012-07-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 60068-2-14:2009 was approved by CENELEC as a European Standard
15、without any modification. _ BS EN 60068-2-14:2009- 3 - EN 60068-2-14:2009 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 refere
16、nces, only the edition cited applies. For undated references, the latest edition of the referenced document (including 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/
17、HD Year IEC 60068 Series Environmental testing EN 60068 Series IEC 60068-2-1 -1)Environmental testing - Part 2-1: Tests - Test A: Cold EN 60068-2-1 20072)IEC 60068-2-2 -1)Environmental testing - Part 2-2: Tests - Test B: Dry heat EN 60068-2-2 20072)IEC 60068-2-17 -1)Environmental testing - Part 2-17
18、: Tests - Test Q: Sealing EN 60068-2-17 19942)IEC Guide 104 -1)The preparation of safety publications and the use of basic safety publications and group safety publications - - 1)Undated reference. 2)Valid edition at date of issue. BS EN 60068-2-14:2009 2 60068-2-14 IEC:2009 CONTENTS INTRODUCTION.6
19、1 Scope.7 2 Normative references .7 3 Field conditions of changing temperature .7 4 General 8 4.1 Design of change of temperature tests 8 4.2 Test parameters 8 4.3 Purpose and choice of the tests 8 4.4 Choice of the duration of the exposure 8 4.5 Choice of the duration of the transfer time.9 4.6 App
20、licability limits of change of temperature tests .9 5 Guidance for the selection of the kind of test 10 6 Initial and final measurements 10 6.1 Initial measurements .10 6.2 Final measurements 10 7 Test Na: Rapid change of temperature with prescribed time of transfer 10 7.1 General description of the
21、 test.10 7.2 Testing procedure .10 7.2.1 Testing chamber10 7.2.2 Mounting or supporting of the test specimen11 7.2.3 Severities 11 7.2.4 Conditioning 11 7.2.5 Test cycle11 7.3 Recovery.12 7.4 Information to be given in the relevant specification 12 8 Test Nb: Change of temperature with specified rat
22、e of change .13 8.1 General description of the test.13 8.2 Testing procedure .13 8.2.1 Testing chamber13 8.2.2 Mounting or supporting of the test specimen13 8.2.3 Severities 13 8.2.4 Conditioning 14 8.2.5 Test cycle14 8.3 Recovery.15 8.4 Information to be given in the relevant specification 15 9 Tes
23、t Nc: Rapid change of temperature, two-fluid-bath method 16 9.1 General description of the test.16 9.2 Testing procedure .16 9.2.1 Testing equipment .16 9.2.2 Severities 16 9.2.3 Conditioning 16 9.3 Test cycle16 9.4 Recovery.17 9.5 Information to be given in the relevant specification 17 BS EN 60068
24、-2-14:200960068-2-14 IEC:2009 3 10 Information to be given in the test report 18 Figure 1 Determination of test duration time (t1).9 Figure 2 Na test cycle 12 Figure 3 Nb test cycle 15 Figure 4 Nc test cycle 17 BS EN 60068-2-14:2009 6 60068-2-14 IEC:2009 INTRODUCTION A change of temperature test is
25、intended to determine the effect on the specimen of a change of temperature or a succession of changes of temperature. It is not intended to show effects which are due only to high or low temperatures. For these effects, the dry heat test or the cold test should be used. The effect of such tests is
26、determined by values of high and low conditioning temperature between which the change is to be effected, the conditioning times for which the test specimen is kept at these temperatures, the rate of change between these temperatures, the number of cycles of conditioning, the amount of heat transfer
27、 into or from the specimen. Guidance on the choice of suitable test parameters for inclusion in the detail specification is given throughout this standard. BS EN 60068-2-14:200960068-2-14 IEC:2009 7 ENVIRONMENTAL TESTING Part 2-14: Tests Test N: Change of temperature 1 Scope This part of IEC 60068 p
28、rovides a test to determine the ability of components, equipment or other articles to withstand rapid changes of ambient temperature. The exposure times adequate to accomplish this will depend upon the nature of the specimen. 2 Normative references The following referenced documents are indispensabl
29、e 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 (all parts), Environmental testing IEC 60068-2-1, Environmental testing Part 2-1: Tests Te
30、st A: Cold IEC 60068-2-2, Environmental testing Part 2-2: Tests Test B: Dry heat IEC 60068-2-17, Environmental testing Part 2-17: Tests Test Q: Sealing IEC Guide 104, The preparation of safety publications and the use of basic safety publications and group safety publications 3 Field conditions of c
31、hanging temperature It is common in electronic equipment and components that changes of temperature occur. Parts inside equipment undergo slower changes of temperature than those on an external surface when the equipment is not switched on. Rapid changes of temperature may be expected when equipment
32、 is transported from warm indoor environments into cold open air conditions or vice versa, when equipment is suddenly cooled by rainfall or immersion in cold water, in externally mounted airborne equipment, under certain conditions of transportation and storage. Components will undergo stresses due
33、to changing temperature when high temperature gradients build up in an equipment after being switched on, e.g. in the neighbourhood of high wattage resistors, radiation can cause rise of surface temperature in neighbouring components while other portions are still cool. Artificially cooled component
34、s may be subjected to rapid temperature changes when the cooling system is switched on. Rapid changes of temperature in components may also be induced during manufacturing processes of equipment. Both the number and amplitude of temperature changes and the time interval between them are important. B
35、S EN 60068-2-14:2009 8 60068-2-14 IEC:2009 4 General 4.1 Design of change of temperature tests Tests Na, Nb and Nc comprise alternate periods at a high and at a low temperature with well-defined transfers from one temperature to the other. The conditioning run from laboratory ambient to the first co
36、nditioning temperature, then to the second conditioning temperature, then back to laboratory ambient is considered one test cycle. 4.2 Test parameters Test parameters comprise the following: laboratory ambient; high temperature; low temperature; duration of exposure; transfer time or rate of change;
37、 number of test cycles. The high and low temperatures are understood to be ambient temperatures which will be reached by most specimens with a certain time-lag. Only in exceptional cases may they be specified outside the normal storage or operating temperature range of the object under test. The tes
38、t is accelerated because the number of severe changes of temperature in a given period is greater than that which will occur under field conditions. 4.3 Purpose and choice of the tests Change of temperature testing is recommended in the following cases: evaluation of electrical performance during a
39、change of temperature, Test Nb; evaluation of mechanical performance during a change of temperature, Test Nb, evaluation of electrical performance after a specified number of rapid changes of temperature, Test Na or Test Nc; evaluation of the suitability of mechanical components, and of materials an
40、d combinations of materials to withstand rapid changes of temperature, Test Na or Test Nc; evaluation of the suitability of construction of components to withstand artificial stressing, Test Na or Test Nc. The change of temperature tests specified in the IEC 60068 series is not intended to evaluate
41、the difference in material constants or electrical performance when operating under temperature stability at the two extremes of temperature. 4.4 Choice of the duration of the exposure The duration of the exposure should be based on the requirements stated in 7.2.3, 8.2.3 or 9.2.2, or as stated in t
42、he relevant specification, keeping in mind the following points: a) The exposure begins as soon as the specimen is in the new environment. b) Stabilization occurs when the temperature difference (T) between the specimen and the test medium is within 3 K to 5 K, or as stated in the test specification
43、. The stabilization period, (ts), is from the start of exposure until the time when the temperature is within the BS EN 60068-2-14:200960068-2-14 IEC:2009 9 specified difference. A representative point (or points) on the specimen may be used for this measurement. c) The test duration, t1, shall be l
44、onger than the specimen stabilization time, ts. Figure 1 provides a graphical representation of the process. This may not be appropriate for heat generating specimens. TBTAt1Temperature of the specimen Time tsTemperature T IEC 2237/08 Figure 1 Determination of test duration time (t1) 4.5 Choice of t
45、he duration of the transfer time If, in the case of the two-chamber method, because of the large size of the specimens the transfer time cannot be made in 3 min, the transfer time may be increased without an appreciable influence on the test results as follows: t2 0,05 tswhere t2is the duration of t
46、he transfer time; tsis the stabilisation period of the specimen. 4.6 Applicability limits of change of temperature tests Inside a specimen, the temperature change rate depends on the heat conduction of its materials, the spatial distribution of its heat capacity and its dimensions. The change of tem
47、perature at a point on the surface of a specimen follows approximately an exponential law. Inside large specimens, such alternate exponential rises and decreases may lead to periodic and approximately sinusoidal changes of temperature with much lower amplitudes than the applied temperature swing. Th
48、e mechanism of heat transfer between the test specimen and the conditioning medium in the chamber or bath should be taken into account. Liquid in motion leads to very high rates of change of temperature on the surface of the specimens and still air to very low rates. The two-bath method with water a
49、s a conditioning medium (Test Nc) should be restricted to specimens which are either sealed or are by their nature insensitive to water, since their performance and properties may deteriorate by immersion. BS EN 60068-2-14:2009 10 60068-2-14 IEC:2009 In particular cases, such as with specimens sensitive to water, a test with liquid other than water may need to be specified. When designing such a test, the characteristics of
