IEC 60068-2-14:2023

IEC 60068-2-14 ®
Edition 7.0 2023-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Environmental testing –
Part 2-14: Tests – Test N: Change of temperature

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IEC 60068-2-14 ®
Edition 7.0 2023-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Environmental testing –
Part 2-14: Tests – Test N: Change of temperature
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 19.040 ISBN 978-2-8322-7338-8

– 2 – IEC 60068-2-14:2023 RLV © 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 change of temperature tests with temperature change . 9
5.3 Test parameters . 9
5.4 Purpose and choice of the tests . 10
5.5 Choice of the duration of the exposure time to each conditioning
temperature . 10
5.6 Choice of the duration of the transfer time t . 11
5.7 Applicability limits of change of temperature tests . 12
5 Guidance for the selection of the kind of test .
6 Initial and final measurements . 13
6.1 General . 13
6.2 Initial measurements . 13
6.3 Final measurements . 13
7 Test Na: Rapid change of temperature with prescribed time of transfer . 13
7.1 General description of the test . 13
7.2 Testing procedure . 13
7.2.1 Testing chamber . 13
7.2.2 Mounting or supporting of the test specimen . 16
7.2.3 Severities . 16
7.2.4 Conditioning Preconditioning . 18
7.2.5 Test cycle . 18
7.3 Recovery . 21
7.4 Information to be given in the relevant specification .
8 Test Nb: Change of temperature with specified rate of change . 22
8.1 General description of the test . 22
8.2 Testing procedure . 22
8.2.1 Testing chamber . 22
8.2.2 Mounting or supporting structure of the test specimen . 23
8.2.3 Severities . 23
8.2.4 Tolerance . 24
8.2.5 Conditioning Preconditioning . 25
8.3 Test cycle . 25
8.4 Recovery . 27
8.4 Information to be given in the relevant specification .
9 Test Nc: Rapid change of temperature, two-fluid-bath method . 27
9.1 General description of the test . 27
9.2 Testing procedure . 28
9.2.1 Testing equipment . 28
9.2.2 Severities . 28

9.2.3 Conditioning . 28
9.3 Test cycle . 28
9.4 Recovery . 30
9.5 Information to be given in the relevant specification .
10 Information to be given in the test report. 31
Annex A (informative) Potential consequences of improper severities . 33
Annex B (informative) Thermal responsiveness of different materials and geometries . 34
Annex C (normative) Auxiliary table with exemplary temperature tolerances ±σT for
preferred combinations of high and low conditioning temperatures and rates of
temperature change (Test Nb) . 35
Bibliography . 41

Figure 1 – Determination of test duration time (t ) the exposure time t of the specimen
1 1
to each conditioning temperature . 11
Figure 2 – Schematic representation of examples of thermal test cabinets and test
procedure with two separate test chambers . 14
Figure 3 – Schematic representation of examples of thermal test cabinets with one test
chamber . 15
Figure 4 – Possibility of condensation during rapid temperature change . 16
Figure 5 – Possibility of condensation during transfer of the specimen . 16
Figure 6 – Increased severity of Test Na . 17
Figure 2 – Na test cycle .
Figure 7 – Na test cycle, one-chamber method . 19
Figure 8 – Na test cycle, two-chamber method . 21
Figure 9 – Tolerance for fluctuation of test temperatures . 25
Figure 10 – Nb test cycle . 26
Figure 11 – Test times for intermediate operation of specimens . 27
Figure 12 – Nc test cycle . 30
Figure A.1 – Delayed temperature change of the specimen . 33
Figure B.1 – Rate of temperature change of specimen with differing thermal

responsiveness . 34
Figure C.1 – Tolerance for fluctuation of test temperatures for exemplary test
parameters . 36

Table C.1 – Applicable temperature tolerances ±σ in K for preferred combinations of
T
high and low conditioning temperatures and rates of temperature change dT . 37
R
– 4 – IEC 60068-2-14:2023 RLV © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-14: Tests – Test N: Change of temperature

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