IEC 60068-2-14
Edition 7.0 2023-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-14: Tests – Test N: Change of temperature
Essais d'environnement –
Partie 2-14: Essais – Essai N: Variation de température
IEC 60068-2-14:2023-07(en-fr)
®
IEC 60068-2-14
Edition 7.0 2023-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-14: Tests – Test N: Change of temperature
Essais d'environnement –
Partie 2-14: Essais – Essai N: Variation de température
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040
ISBN 978-2-8322-7265-7
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
®
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.
– 2 – IEC 60068-2-14:2023 © IEC 2023
CONTENTS
FOREWORD ........................................................................................................................... 4
INTRODUCTION ..................................................................................................................... 6
1 Scope .............................................................................................................................. 7
2 Normative references ...................................................................................................... 7
3 Terms and definitions ...................................................................................................... 7
4 Symbols .......................................................................................................................... 8
5 General ........................................................................................................................... 8
5.1 Field conditions of changing temperature ................................................................ 8
5.2 Design of tests with temperature change ................................................................. 9
5.3 Test parameters ...................................................................................................... 9
5.4 Purpose and choice of the tests ............................................................................ 10
5.5 Choice of the exposure time to each conditioning temperature .............................. 10
5.6 Choice of the duration of the transfer time t
2
........................................................ 11
5.7 Applicability limits of change of temperature tests ................................................. 11
6 Initial and final measurements ....................................................................................... 12
6.1 General ................................................................................................................. 12
6.2 Initial measurements ............................................................................................. 12
6.3 Final measurements .............................................................................................. 12
7 Test Na: Rapid change of temperature .......................................................................... 12
7.1 General description of the test .............................................................................. 12
7.2 Testing procedure ................................................................................................. 12
7.2.1 Testing chamber ............................................................................................ 12
7.2.2 Mounting or supporting of the test specimen .................................................. 15
7.2.3 Severities ...................................................................................................... 15
7.2.4 Preconditioning .............................................................................................. 16
7.2.5 Test cycle ...................................................................................................... 17
7.3 Recovery .............................................................................................................. 19
8 Test Nb: Change of temperature with specified rate of change ...................................... 19
8.1 General description of the test .............................................................................. 19
8.2 Testing procedure ................................................................................................. 20
8.2.1 Testing chamber ............................................................................................ 20
8.2.2 Mounting or supporting structure of the test specimen ................................... 20
8.2.3 Severities ...................................................................................................... 20
8.2.4 Tolerance ...................................................................................................... 21
8.2.5 Preconditioning .............................................................................................. 22
8.3 Test cycle ............................................................................................................. 22
8.4 Recovery .............................................................................................................. 23
9 Test Nc: Rapid change of temperature, two-fluid-bath method ....................................... 24
9.1 General description of the test .............................................................................. 24
9.2 Testing procedure ................................................................................................. 24
9.2.1 Testing equipment ......................................................................................... 24
9.2.2 Severities ...................................................................................................... 24
9.2.3 Conditioning .................................................................................................. 24
9.3 Test cycle ............................................................................................................. 25
9.4 Recovery .............................................................................................................. 25
10 Information to be given in the test report........................................................................ 26
IEC 60068-2-14:2023 © IEC 2023 – 3 –
Annex A (informative) Potential consequences of improper severities .................................. 27
Annex B (informative) Thermal responsiveness of different materials and geometries .......... 28
Annex C (normative) Auxiliary table with exemplary temperature tolerances ±σ
T
for
preferred combinations of high and low conditioning temperatures and rates of
temperature change (Test Nb) .............................................................................................. 29
Bibliography .......................................................................................................................... 35
Figure 1 – Determination of the exposure time t
1
of the specimen to each conditioning
temperature .......................................................................................................................... 11
Figure 2 – Schematic representation of examples of thermal test cabinets and test
procedure with two separate test chambers .......................................................................... 13
Figure 3 – Schematic representation of examples of thermal test cabinets with one test
chamber ............................................................................................................................... 14
Figure 4 – Possibility of condensation during rapid temperature change ............................... 15
Figure 5 – Possibility of condensation during transfer of the specimen .................................. 15
Figure 6 – Increased severity of Test Na ............................................................................... 16
Figure 7 – Na test cycle, one-chamber method ..................................................................... 17
Figure 8 – Na test cycle, two-chamber method ...................................................................... 19
Figure 9 – Tolerance for fluctuation of test temperatures ...................................................... 22
Figure 10 – Nb test cycle ...................................................................................................... 23
Figure 11 – Test times for intermediate operation of specimens ............................................ 23
Figure 12 – Nc test cycle ...................................................................................................... 25
Figure A.1 – Delayed temperature change of the specimen ................................................... 27
Figure B.1 – Rate of temperature change of specimen with differing thermal
responsiveness ..................................................................................................................... 28
Figure C.1 – Tolerance for fluctuation of test temperatures for exemplary test
parameters ........................................................................................................................... 30
Table C.1 – Applicable temperature tolerances ±σ
T
in K for preferred combinations of
high and low conditioning temperatures and rates of temperature change dT
R
..................... 31
– 4 – IEC 60068-2-14:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-14: Tests – Test N: Change of temperature
FOREWORD
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IEC 60068-2-14 has been prepared by IEC technical committee 104: Environmental conditions,
classification and methods of test. It is an International Standard.
This seventh edition cancels and replaces the sixth edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updating of the figures for clarification purposes;
b) updating of specimen temperature(s) and severities as well as tolerances for change of
temperature tests;
c) revision of standardized requirements for test reports for Tests Na and Nb.
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