SIST EN IEC 60068-2-14:2024

SLOVENSKI STANDARD
01-maj-2024
Nadomešča:
SIST EN 60068-2-14:2009
Okoljsko preskušanje - 2-14. del: Preskusi - Preskus N: Temperaturne spremembe
(IEC 60068-2-14:2023)
Environmental testing - Part 2-14: Tests - Test N: Change of temperature (IEC 60068-2-
14:2023)
Umgebungseinflüsse - Teil 2-14: Prüfverfahren - Prüfung N: Temperaturwechsel (IEC
60068-2-14:2023)
Essais d'environnement - Partie 2-14: Essais - Essai N: Variation de température (IEC
60068-2-14:2023)
Ta slovenski standard je istoveten z: EN IEC 60068-2-14:2023
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60068-2-14

NORME EUROPÉENNE
EUROPÄISCHE NORM September 2023
ICS 19.040 Supersedes EN 60068-2-14:2009
English Version
Environmental testing - Part 2-14: Tests - Test N: Change of
temperature
(IEC 60068-2-14:2023)
Essais d'environnement - Partie 2-14: Essais - Essai N: Umgebungseinflüsse - Teil 2-14: Prüfverfahren - Prüfung N:
Variation de température Temperaturwechsel
(IEC 60068-2-14:2023) (IEC 60068-2-14:2023)
This European Standard was approved by CENELEC on 2023-08-31. CENELEC members are bound to comply 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60068-2-14:2023 E

European foreword
The text of document 104/991/FDIS, future edition 7 of IEC 60068-2-14, prepared by IEC/TC 104
"Environmental conditions, classification and methods of test" was submitted to the IEC-CENELEC
parallel vote and approved by CENELEC as EN IEC 60068-2-14:2023.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-05-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-08-31
document have to be withdrawn
This document supersedes EN 60068-2-14:2009 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60068-2-14:2023 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60068 series NOTE Approved as EN 60068 series
IEC 60068-2-6 NOTE Approved as EN 60068-2-6
IEC 60068-2-17 NOTE Approved as EN 60068-2-17
IEC 60068-2-30 NOTE Approved as EN 60068-2-30
IEC 60068-2-67 NOTE Approved as EN 60068-2-67
IEC 60068-3-1 NOTE Approved as EN 60068-3-1
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60068-2-1 - Environmental testing - Part 2-1: Tests - Test A: EN 60068-2-1 -
Cold
IEC 60068-2-2 - Environmental testing - Part 2-2: Tests - Test B: EN 60068-2-2 -
Dry heat
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

– 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 . 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 for
T
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 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 in K for preferred combinations of
T
high and low conditioning temperatures and rates of temperature change dT . 31
R
– 4 – IEC 60068-2-14:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-14: Tests – Test N: Change of temperature

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 international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual 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 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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch or
www.iso.org/patents. IEC shall not be held responsible for identifying any or all such patent rights.
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.

IEC 60068-2-14:2023 © IEC 2023 – 5 –
The text of this International Standard is based on the following documents:
Draft Report on voting
104/991/FDIS 104/1016/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 60068 series, published under the general title Environmental testing,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60068-2-14:2023 © IEC 2023
INTRODUCTION
A change of temperature test is 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 that are caused by low or high temperature exposure. For
these effects, the cold test or the dry heat test, as specified in IEC 60068-2-1 and
IEC 60068-2-2, should be used.
The effect of change of temperature tests is determined by
– values of high and low conditioning temperature between which the change is to be affected,
– 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 into or from the specimen,
– the thermal conductivity and the materials of the specimen,
– the rate of change of the specimen’s temperature on its surface (respectively in relevant
positions) or in its core.
Guidance on the choice of suitable test parameters for inclusion in the detail specification is
given throughout this document.

IEC 60068-2-14:2023 © IEC 2023 – 7 –
ENVIRONMENTAL TESTING –
Part 2-14: Tests – Test N: Change of temperature

1 Scope
This document provides tests with specified ambient temperature changes to analyse their
impacts on specimens.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60068-2-1 and
IEC 60068-2-2 apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp

– 8 – IEC 60068-2-14:2023 © IEC 2023
4 Symbols
temperature difference between high conditioning temperature T and low
B
D
conditioning temperature T
A
low conditioning temperature
T
A
decreased low conditioning temperature
T
Ad
high conditioning temperature
T
B
increased high conditioning temperature
T
Bi
temperature of standard atmospheric conditions for measurement and tests
T
STD
(15 °C to 35 °C)
temperature difference between the specimen and the test medium (e.g. air)
ΔT
s
temperature change rate (Test Nb)
dT
R
stabilization time of specimen temperature
t
s
stabilization time of specimen temperature during the first cycle, starting from
t
s*
laboratory air temperature
exposure time of the specimen to each conditioning temperature
t
transfer time of the specimen from one test chamber to another (two-chamber
t
test method)
applicable temperature tolerance of the medium temperature during temperature
±𝜎𝜎
T
transition (Test Nb)
applicable temperature tolerance of the medium temperature during the constant
±𝜎𝜎
Tconst
conditioning
5 General
5.1 Field conditions of changing 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 can be expected
– when equipment is transported from warm indoor into cold outdoor environments or vice
versa,
– when equipment is suddenly cooled by rainfall or immersion in cold water,
– when equipment is attached or in close proximity to components leading to high thermal
stress (e.g. combustion engines, central processing units),
– when equipment is artificially cooled or heated,
– in externally mounted airborne equipment or when equipment is located in unheated aircraft
or cargo holds,
– under certain conditions of transportation and storage.

IEC 60068-2-14:2023 © IEC 2023 – 9 –
Components will undergo stresses due to changing temperature when high temperature
gradients build up in an equipment after being switched on, for example in the proximity of high
power resistors, radiation can cause rise of the surface temperature on close components while
other portions remain cold.
Artificially cooled components can be subjected to rapid temperature changes when the cooling
system is switched on. Rapid changes of temperature in components can also be induced during
manufacturing processes or the transportation of equipment. Both the number and amplitude of
temperature changes, the time interval between them and the thermal responsiveness of the
equipment (or specimen) are important.
5.2 Design of tests with temperature change
Change of temperature Tests Na, Nb and Nc comprise alternate periods at a high and a low
temperature with well-defined transfers from one temperature to the other. The conditioning run
from the laboratory ambient temperature to the first conditioning temperature, then to the
second conditioning temperature, then back to the laboratory ambient temperature is
considered as one test cycle.
5.3 Test parameters
Test parameters comprise the following:
– laboratory ambient conditions (mainly temperature and humidity);
– high conditioning temperature T ;
B
– increased high conditioning temperature T , if applicable;
Bi
– low conditioning temperature T ;
A
– decreased low conditioning temperature T , if applicable;
Ad
– exposure time t of the specimen to each conditioning temperature;
– transfer time t or temperature change rate dT ;
2 R
– number of test cycles.
As these tests are intended to validate the effects of temperature changes on the specimen,
the specimen’s characteristics should always be taken into consideration (if not specified
otherwise):
– thermal responsiveness of the specimen in affected areas or the core;
• thermal conductivity;
• specific heat capacity;
– density;
– geometry;
– mass.
The experimental determination of these characteristics is recommended, if unknown and not
specified otherwise.
The test is accelerated because the number of severe changes of temperature in a given period
is greater than that which will occur under field conditions.
The high and low conditioning temperatures are understood to be ambient temperatures which
will be reached by most specimens with a certain time lag. It is recommended to consider the
specimen’s characteristics when specifying the test. Annex A gives further information on
potential consequences of improper severities of tests.

– 10 – IEC 60068-2-14:2023 © IEC 2023
Only in exceptional cases should these temperatures be specified outside the normal storage
or operating temperature range of the object under test.
NOTE If the specimen’s characteristics (mass, density, geometry) prevent the specified rate of change, the
temperatures can be specified outside the normal storage or operating temperatures to increase the severity of the
intended test, if not specified otherwise.
5.4 Purpose and choice of the tests
Change of temperature testing is recommended in the following cases:
– 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 and 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;
– evaluation of electrical performance as a consequence of a change of temperature, Test Nb;
– evaluation of mechanical performance as a consequence of a change of temperature,
Test Nb.
The change of temperature tests specified in the IEC 60068 series is not intended to evaluate
the difference in material constants or electrical performance when operating under the
conditioning temperatures T and T .
A B
5.5 Choice of the exposure time to each conditioning temperature
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 the 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 between the specimen and the test
medium (ΔT ) is within 5 K, or as stated in the test specification. The stabilization time of
s
specimen temperature t is from the start of exposure until the moment when the
s
temperature is within the specified difference. A representative point (or points) on the
specimen can be used for this measurement.
c) The exposure time t of the specimen to each conditioning temperature shall be longer than
the stabilization time of the specimen temperature t . Figure 1 provides a graphical
s
representation of the process. It is possible that this will not be appropriate for heat
generating specimens.
IEC 60068-2-14:2023 © IEC 2023 – 11 –

Figure 1 – Determination of the exposure time t of the specimen
to each conditioning temperature
5.6 Choice of the duration of the transfer time t
If, for example owing to the large size of the specimens, the transfer time t cannot be kept
within 3 min, the transfer time can be increased with a negligible influence on the test results
as follows:
t ≤ 0,05 t
2 s
This applies for the two-chamber test (see 7.2.1) method only. When using the one-chamber
is not applicable.
test method, period t
5.7 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 as well as on its dimensions and surface area. A
representative point (or points) on (or inside) the specimen can be used for the measurement
of the temperature change rates.
NOTE 1 The rate of temperature change of specimens made of the same material and mass can vary if their surfaces
differ from each other.
The change of temperature at one point on the surface of a specimen follows approximately an
exponential law. Inside large specimens, such alternate exponential rises and decreases can
lead to periodic and approximately sinusoidal changes of temperature with much lower
amplitudes than the applied temperature swing. Annex B gives further information on the
thermal responsiveness of different materials and geometries.
The mechanism of heat transfer between the test specimen and the conditioning medium in the
chamber or bath should be considered. 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.
NOTE 2 If more than one specimen is tested in the same test chamber, a uniform incoming airflow can be disturbed.
For further information on the relation of airflow and specimen temperature, IEC 60068-3-1 can be helpful.
The two-bath method with water as 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 can deteriorate by immersion.

– 12 – IEC 60068-2-14:2023 © IEC 2023
In particular cases, such as with specimens sensitive to water, a test with liquid other than water
should be specified. When designing such a test, the characteristics of heat transfer of the
liquid, which can differ from those of water, shall be considered.
NOTE 3 To assess the applicability of the two-bath method, evaluations from Test Q: Sealing (IEC 60068-2-17) can
be helpful.
The application of Tests N is preferred as part of a sequence of tests. It is possible that some
types of damage will not become apparent by the final measurements of a Test N but will appear
only during subsequent tests.
An exemplary sequence of tests can be IEC 60068-2-17 Test Q: Sealing, IEC 60068-2-6 Test
Fc: Vibration (sinusoidal), IEC 60068-2-30 Test Db: Damp heat, cyclic (12 h + 12 h cycle) or
IEC 60068-2-67 Test Cy: Damp heat.
The change of temperature Test Nc (Two-bath method) should not be used as an alternative to
Test Q (Sealing).
When specifying a change of temperature test, the properties of the objects under test which
are affected by conditions of changing temperature, and their possible failure mechanisms,
should be kept in mind. The initial and the final measurements should be specified accordingly.
6 Initial and final measurements
6.1 General
Tests Na, Nb and Nc all use the same initial and final measurements.
6.2 Initial measurements
The specimen shall be visually examined and electrically and mechanically checked, as
required by the relevant specification.
6.3 Final measurements
The specimen shall be visually examined and electrically and mechanically checked, as
required by the relevant specification.
7 Test Na: Rapid change of temperature
7.1 General description of the test
This test determines 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. The specimen shall be either in the unpacked, switched-off,
ready for use state, or as otherwise specified in the relevant specification. The specimen is
exposed to rapid changes of temperature in air, or in a suitable inert gas, by alternating
exposure to a low and a high conditioning temperature.
7.2 Testing procedure
7.2.1 Testing chamber
Two separate chambers (two-chamber method, see Figure 2) or one rapid temperature change
rate chamber (one-chamber method, see Figure 3) can be used. If two chambers are used, one
for the low temperature and one for the high temperature, the location shall be such as to allow
transfer of the specimen from one chamber to the other within the specified time. Either manual
or automatic transfer methods can be used.

IEC 60068-2-14:2023 © IEC 2023 – 13 –
Some two-chamber method systems are known as thermal shock test cabinets. These systems
combine characteristics of two separate test chambers and are equipped with a mobile lifting
cage (applies for horizontal shock test chambers as well) for the automatic transfer of the
specimens from one chamber to another (see Figure 2).
Damper shock test cabinets are another embodiment of a one-chamber test system. These
systems contain two conditioning and one test chamber. The test chamber is alternately
exposed to conditioned air from a hot respectively cold conditioning chamber via air flaps (see
Figure 3). No physical transfer is required and the transfer time t is not applicable, when using
this kind of test systems.
Damper shock test cabinets with a stationary test chamber, a hot chamber and a cold chamber
are commonly capable of two-zone tests with hot respectively cold exposure. Some are capable
of three-zone tests, including exposure to ambient air.
NOTE 1 Damper and basket-type test cabinets are often used for Test Na. Depending on the performance, two
separate chambers or one rapid temperature change rate chamber are often used for Test Na as well. One rapid
temperature change rate chamber is often used for Test Nb.

Key
A hot chamber B cold chamber C specimen
D mobile cage E stationary test space

Figure 2 – Schematic representation of examples of thermal test cabinets
and test procedure with two separate test chambers

– 14 – IEC 60068-2-14:2023 © IEC 2023

Key
A hot chamber B cold chamber C specimen
D air flaps E stationary test space

Figure 3 – Schematic representation of examples of thermal
test cabinets with one test chamber
The chambers should be capable of maintaining the working space at the required temperatures.
After insertion of the test specimens, the temperature of the test medium shall be within the
specified tolerance after a time of not more than 10 % of the exposure time t of the specimen
to each conditioning temperature. The temperature of the test medium refers to the control
sensor of the test chamber, if not specified otherwise.
Owing to the specimen’s lower rate of temperature change, its temperature can fall below the
dew point temperature when bringing the specimens in the hot test environment (see Figure 4)
or exposing them to ambient laboratory air (see Figure 5). During the rapid change to the high
temperature T or when transferring the specimens from the cold chamber to the hot chamber,
B
condensation of ambient air humidity should always be taken into consideration.
NOTE 2 Depending on the heat capacity and mass of the specimen, this phenomenon can be more or less
pronounced.
Dehumidification during heating phases or compressed air dryers can be used to prevent
condensation on the specimen’s surface, if necessary.

IEC 60068-2-14:2023 © IEC 2023 – 15 –

Figure 4 – Possibility of condensation during rapid temperature change

Figure 5 – Possibility of condensation during transfer of the specimen
7.2.2 Mounting or supporting of the test specimen
The thermal conduction of the mounting or supports shall be low, such that for practical
purposes the specimen is thermally isolated, if not specified otherwise. When testing several
specimens simultaneously they shall be so placed that free circulation shall be provided
between specimens, and between specimens and chamber surfaces.
7.2.3 Severities
The severity of the test is defined by the combination of the two temperatures, the transfer time,
the exposure time of the specimen and the number of cycles.
The low conditioning temperature T shall be specified in the relevant specification and shall
A
be chosen from the test temperatures of either IEC 60068-2-1 or IEC 60068-2-2 or both, if not
specified otherwise.
The high conditioning temperature T shall be specified in the relevant specification and shall
B
be chosen from the test temperatures of either IEC 60068-2-1 or IEC 60068-2-2 or both, if not
specified otherwise.
– 16 – IEC 60068-2-14:2023 © IEC 2023
The exposure time t to each of the two conditioning temperatures depends on the heat capacity
of the specimen. It can be 3 h, 2 h, 1 h, 30 min or 10 min, or as specified in the relevant
specification. Where no exposure period is specified in the relevant specification, it is
understood to be 3 h.
NOTE The 10 min exposure time often applies to the testing of small specimens that achieve temperature
stabilization without a significant time lag.
If temperature stabilization of the specimens cannot be achieved within the chosen exposure
time, for example owing to a high heat capacity of the specimens, the severity of the test can
be temporarily increased. The severity shall only be increased until temperature stabilization is
achieved. A representative point (or points) on (or inside) the specimen can be used for this
measurement. A higher severity of the test is achieved by increasing the temperature difference
between the low conditioning temperature T and the high conditioning temperature T . Figure 6
A B
provides a graphical representation of an increased severity.

Key
A start of first cycle
B end of first cycle and start of second cycle
Figure 6 – Increased severity of Test Na
The decreased low conditioning temperature T and the increased high conditioning
Ad
temperature T should be chosen from the test temperatures of either IEC 60068-2-1 or
Bi
IEC 60068-2-2 or both, if not specified otherwise.
When choosing the increased high conditioning temperature T and the decreased low
Bi
conditioning temperature T the temperature limits of the specimen should be respected to
Ad
avoid possible damage caused by the chosen temperature differences, if not specified
otherwise. The chosen conditioning temperatures shall be given in the test report.

The preferred number of test cycles is 5, unless otherwise specified in the relevant specification.
7.2.4 Preconditioning
The specimen and the temperature in the test chamber shall be at the temperature of standard
atmospheric conditions for measurement and test T , 15 °C to 35 °C. If required by the
STD
relevant specification, the specimen shall be brought into operating conditions.

IEC 60068-2-14:2023 © IEC 2023 – 17 –
7.2.5 Test cycle
a) One-chamber test method
The specimen shall be brought into the test chamber and be exposed to the temperature change
to the low conditioning temperature T (see Figure 7).
A
The low conditioning temperature T shall be maintained for the specified exposure time t
A 1
(see 5.5). t includes an initial time, not longer than 0,1 t for temperature stabilization of the
1 1
test medium.
Figure 7 – Na test cycle, one-chamber method
NOTE 1 The exposure time is measured from the beginning of change of temperature within the chamber.
Temperature stabilization of the specimen (ΔT ) can be achieved in the specified period t (see
s 1
Figure 7), if not specified otherwise. The time required for this is indicated with t .
s
NOTE 2 In some cases it can become necessary to extend t to promote temperature equalization of the specimen
or to initiate a certain relaxation process.
The specimen shall then be exposed to the temperature change to the high conditioning
temperature T .
B
The high conditioning temperature T shall be maintained for the specified exposure time t . t
B 1 1
includes an initial time, not longer than 0,1 t for temperature stabilization of the test medium.
Temperature stabilization of the specimen (ΔT ) can be achieved in the specified period t (see
s 1
.
Figure 7), if not specified otherwise. The time required for this is indicated with t
s
NOTE 3 In some cases it can become necessary to extend t to promote temperature equalization of the specimen
or to initiate a certain relaxation process.
For the next cycle the specimen shall be exposed to the low conditioning temperature T .
A
One cycle comprises the exposure time t to both conditioning temperatures. At the end of the
last cycle, the specimen shall be subjected to the recovery procedure (see 7.3).

---------------------- P
...