Environmental testing - Part 3-6: Supporting documentation and guidance - Confirmation of the performance of temperature/ humidity chambers

IEC 60068-3-6:2018 is available as IEC 60068-3-6:2018 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60068-3-6:2018 provides a uniform and reproducible method of confirming that temperature and humidity test chambers, without specimens, conform to the requirements specified in climatic test procedures of IEC 60068-2 (all parts). This document is intended for users when conducting regular chamber performance monitoring. This second edition cancels and replaces the first edition published in 2001. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- Confirmation procedures are clarified.
The French version of this standard has not been voted upon.

Essais d'environnement - Partie 3-6: Documentation d'accompagnement et recommandations – Confirmation des performances des chambres d'essai en température/humidité

L'IEC 60068-3-6:2018 fournit une méthode uniforme et reproductible pour confirmer que les chambres d'essai en température et humidité, sans spécimens, respectent les exigences spécifiées dans les procédures d'essai climatique de l'IEC 60068-2 (toutes les parties). Le présent document s'adresse aux utilisateurs qui effectuent une surveillance régulière des performances des chambres.
La présente version bilingue (2019-07) correspond à la version anglaise monolingue publiée en 2018-01.
Cette deuxième édition annule et remplace la première édition parue en 2001. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- Les procédures de confirmation ont été clarifiées.
La version française de cette norme n'a pas été soumise au vote.

General Information

Status
Published
Publication Date
22-Jan-2018
Current Stage
PPUB - Publication issued
Completion Date
23-Jan-2018
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IEC 60068-3-6
Edition 2.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 3-6: Supporting documentation and guidance – Confirmation of the
performance of temperature/humidity chambers
Essais d'environnement –
Partie 3-6: Documentation d'accompagnement et guide – Confirmation des
performances des chambres d'essai en température/humidité
IEC 60068-3-6:2018-01(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60068-3-6
Edition 2.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 3-6: Supporting documentation and guidance – Confirmation of the
performance of temperature/humidity chambers
Essais d'environnement –
Partie 3-6: Documentation d'accompagnement et guide – Confirmation des
performances des chambres d'essai en température/humidité
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040 ISBN 978-2-8322-7180-3

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.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60068-3-6:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

4 Measuring of performances ............................................................................................. 9

4.1 Test area environment ............................................................................................ 9

4.2 Measurement system .............................................................................................. 9

4.3 Temperature measurement system ......................................................................... 9

4.4 Humidity measurement system ............................................................................... 9

4.5 Temperature/humidity chamber test specimens ..................................................... 10

4.6 Specified location of temperature sensors and humidity sensor in working

space .................................................................................................................... 10

4.6.1 General ......................................................................................................... 10

4.6.2 Temperature sensors ..................................................................................... 11

4.6.3 Humidity sensor ............................................................................................. 11

4.7 Measurement method ........................................................................................... 11

4.7.1 General ......................................................................................................... 11

4.7.2 Achieved humidity ......................................................................................... 11

4.7.3 Temperature/humidity stabilization ................................................................ 12

4.7.4 Humidity fluctuation ....................................................................................... 12

4.7.5 Humidity gradient........................................................................................... 13

4.7.6 Humidity variation in space ............................................................................ 14

4.8 Standard humidity sequence ................................................................................. 15

5 Information to be given in the performance test report ................................................... 16

Bibliography .......................................................................................................................... 17

Figure 1 – Example of humidity differences ............................................................................. 8

Figure 2 – Working space ....................................................................................................... 8

Figure 3 – Location of sensors for temperature/humidity chambers up to 2 000 l ................... 10

Figure 4 – Location of minimal additional sensors for temperature/humidity chambers

over 2 000 l ........................................................................................................................... 10

Figure 5 – Example of achieved humidity .............................................................................. 11

Figure 6 – Example of temperature/humidity stabilization ...................................................... 12

Figure 7 – Example of humidity fluctuation ............................................................................ 13

Figure 8 – Example of humidity gradient for chambers up to 2 000 l ...................................... 14

Figure 9 – Example of humidity variation in space for chambers up to 2000 l ........................ 15

Figure 10 – Example of climatogram ..................................................................................... 16

Table 1 – Practical dimensions ............................................................................................... 9

Table 2 – Example of test sequence ..................................................................................... 15

---------------------- Page: 4 ----------------------
IEC 60068-3-6:2018 © IEC 2018 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 3-6: Supporting documentation and guidance –
Confirmation of the performance of temperature/humidity chambers
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,

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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

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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

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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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60068-3-6 has been prepared by IEC technical committee 104:

Environmental conditions, classification and methods of test.

This bilingual version (2019-07) corresponds to the monolingual English version, published in

2018-01.

This second edition cancels and replaces the first edition published in 2001. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) Confirmation procedures are clarified.
---------------------- Page: 5 ----------------------
– 4 – IEC 60068-3-6:2018 © IEC 2018
The text of this International Standard is based on the following documents:
FDIS Report on voting
104/760/FDIS 104/779/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.
The French version of this standard has not been voted upon.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

IEC 60068-3-6 is to be read in conjunction with IEC 60068-3-5:2001 and IEC 60068-3-7:2001.

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 "http://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.
---------------------- Page: 6 ----------------------
IEC 60068-3-6:2018 © IEC 2018 – 5 –
INTRODUCTION

IEC 60068 (all parts) contains fundamental information on environmental testing procedures

and severities.

The expression "environmental conditioning" or "environmental testing" covers the natural and

artificial environments to which components or equipment may be exposed so that an

assessment can be made of their performance under conditions of use, transport and storage

to which they may be exposed in practice.

Temperature and humidity chambers used for "environmental conditioning" or "environmental

testing" are not described in any publication, although the method of maintaining and

measuring temperature and/or humidity has a great influence on test results. The physical

characteristics of temperature and humidity chambers can also influence test results.

---------------------- Page: 7 ----------------------
– 6 – IEC 60068-3-6:2018 © IEC 2018
ENVIRONMENTAL TESTING –
Part 3-6: Supporting documentation and guidance –
Confirmation of the performance of temperature/humidity chambers
1 Scope

This part of IEC 60068 provides a uniform and reproducible method of confirming that

temperature and humidity test chambers, without specimens, conform to the requirements

specified in climatic test procedures of IEC 60068-2 (all parts). This document is intended for

users when conducting regular chamber performance monitoring.
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 60068-3-5:2001, Environmental testing – Part 3-5: Supporting documentation and

guidance – Confirmation of the performance of temperature chambers

IEC 60068-3-7:2001, Environmental testing – Part 3-7: Supporting documentation and

guidance – Measurements in temperature chambers for tests A and B (with load)

IEC 60068-3-11, Environmental testing – Part 3-11: Supporting documentation and guidance

– Calculation of uncertainty of conditions in climatic test chambers
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

NOTE 1 For terms and definitions regarding temperature testing, refer to IEC 60068-3-5.

NOTE 2 Unless otherwise specified, "humidity" is relative humidity (RH).
3.1
temperature/humidity chamber

enclosure or space in some parts of which the temperature/humidity conditions specified in

IEC 60068-2 (all parts) can be achieved
Note 1 to entry: See IEC 60068-3-4.
3.2
absolute humidity
mass of water vapour present in a unit volume of moist air
Note 1 to entry: Typical units of measure are g/m3.
---------------------- Page: 8 ----------------------
IEC 60068-3-6:2018 © IEC 2018 – 7 –
3.3
dewpoint

temperature at which the saturation vapour pressure over water is equal to the partial

pressure of the water vapour in the air
3.4
saturation vapour pressure

maximum possible pressure exerted by a water vapour in equilibrium with its solid or liquid

phase, such that any increase will initiate within the vapour a change to a more condensed

state
3.5
partial vapour pressure

contribution of water vapour in a given volume of air at a constant pressure and temperature

of the atmosphere
3.6
relative humidity

ratio of the partial vapour pressure, divided by the saturation vapour pressure of a given

volume of air at a constant temperature, expressed as percentage

Note 1 to entry: The most popular method to express the water vapour content in air is relative humidity.

3.7
temperature/humidity stabilization

state of maintaining temperature/humidity within specified tolerance for a specified time at

specified points in the working space
3.8
achieved humidity

stabilized humidity which desired humidity at the centre of the working space achieves within

specified tolerance
3.9
climatogram
graphic display of combined temperature with relative humidity
Note 1 to entry: See Figure 9.
3.10
relative humidity fluctuation

difference, after stabilization, between the maximum and minimum humidity at specified points

in the working space during a specified interval of time
Note 1 to entry: For calibration, the centre point of working space may be used.
3.11
relative humidity gradient

maximum difference in mean humidity value, after stabilization, at any moment in time

between two separate points in the working space

Note 1 to entry: The absolute humidity of the air can be considered to be the same throughout the working space.

Note 2 to entry: See Figure 1.
3.12
relative humidity variation in space

difference in mean value, after stabilization, at any moment in time between the humidity at

the centre of the working space and at any other point in the working space
Note 1 to entry: See Figure 1.
---------------------- Page: 9 ----------------------
– 8 – IEC 60068-3-6:2018 © IEC 2018
Humidity fluctuation
outside the centre of
working space
Humidity fluctuation
in the centre of
working space
Humidity fluctuation
outside the centre of
working space
Time
IEC
Figure 1 – Example of humidity differences
3.13
working space

part of the chamber in which the specified conditions can be maintained within the specified

tolerances
Note 1 to entry: See Figure 2 and Table 1.
X X
1 2
IEC
NOTE Practical dimensions of working space see Table 1.
Figure 2 – Working space
Humidity
Variation
Gradient
---------------------- Page: 10 ----------------------
IEC 60068-3-6:2018 © IEC 2018 – 9 –
Table 1 – Practical dimensions
Size Volume Distance X X (min.)
l mm mm
Small Up to 1 000 L/10 50
Medium 1 000 to 2 000 L/10 100
Large More than 2 000 L/10 150
NOTE Not all chambers are cubic in construction.
4 Measuring of performances
4.1 Test area environment

The environment around a temperature/humidity test chamber may influence the conditions

inside the test chamber.

The confirmation of performance of a temperature/humidity chamber should be carried out

under standard atmospheric conditions specified in IEC 60068-1.
4.2 Measurement system

When performing an assessment of a temperature/humidity chamber, a temperature/humidity

measuring system which is independent of the chamber’s control system should be used.

4.3 Temperature measurement system
See IEC 60068-3-5.
4.4 Humidity measurement system
The uncertainty of measurement of the output of the measurement system should be

determined by calibration of the system, traceable to international standards (see ISO 10012),

and the overall measurement uncertainty should be established using ISO/IEC Guide 98-3

related to the expression of uncertainty in measurement.

Some examples of humidity measurement systems include, but are not limited to, those listed

below.
a) Wet and dry bulb method
This method uses the cooling effect of water evaporation from a wet sock. The

temperature of the sock is measured with a temperature sensor whilst simultaneously

measuring the temperature of the air with a second temperature sensor.
b) Dewpoint mirror method
This method cools the surface of the mirror until condensation occurs on it. The
temperature indicated is the dewpoint temperature.
c) Lithium chloride sensor
This method gives absolute humidity values (dewpoint temperature).
d) Capacitive sensor

Permeation of humidity changes the dielectric properties of certain materials and this is

used for direct measurement of relative humidity.
---------------------- Page: 11 ----------------------
– 10 – IEC 60068-3-6:2018 © IEC 2018
4.5 Temperature/humidity chamber test specimens
All measurements described below are performed with an empty working space. For

measuring with test specimens (with or without heat dissipation), see IEC 60068-3-7.

4.6 Specified location of temperature sensors and humidity sensor in working space

4.6.1 General

Temperature measuring sensors are located in each corner and in the centre of the working

space (see Figure 3, minimum 9 sensors). Humidity measuring sensor is located in the centre

of the working space. For temperature/humidity chambers over 2 000 l, additional temperature

sensors should be located in front of the centre of each wall (see Figure 4, minimum

15 sensors).
10 N
Centre
10 1
IEC
Figure 3 – Location of sensors for temperature/humidity chambers up to 2 000 l
IEC
Figure 4 – Location of minimal additional sensors for
temperature/humidity chambers over 2 000 l
---------------------- Page: 12 ----------------------
IEC 60068-3-6:2018 © IEC 2018 – 11 –
4.6.2 Temperature sensors
See IEC 60068-3-5, 4.2.
4.6.3 Humidity sensor

A single humidity sensor shall be positioned at the centre of the working space. The relative

humidity is calculated (by Pernter’s or Sprung’s psychrometric formula) at each point in the

working space where a temperature sensor is located by using the temperature difference.

This assumes that the absolute humidity remains the same throughout the working space.

4.7 Measurement method
4.7.1 General

The confirmation of temperature performance of temperature/humidity chamber shall be

carried out by IEC 60068-3-5. Humidity measurement point is at the centre of the working

space only. The output of the temperature/humidity measuring system (see Figure 3 or

Figure 4) determine, after chamber stabilization, the achieved humidity, humidity fluctuation

and humidity gradient of the working space. For tolerance, the specification of the

temperature/humidity chamber or, as necessary, tolerance specified in IEC 60068-2 (all

parts), is required to maintain at the centre of the working space. Location of sensor is

minimum 9 points or 15 points. This depends on the test chamber size. Measurement method

is explained based on 9 points.

Uncertainty of measurement of the temperature/humidity measuring system shall be according

to IEC 60068-3-11.
4.7.2 Achieved humidity

Humidity at the centre of the working space, shown in Figure 5, has reached and maintained

the set humidity within tolerance.
Tolerance 5
Setting
humidity
IEC

t should be minimum 30 min. N is the humidity at the centre of the working space.

1 5
Figure 5 – Example of achieved humidity
---------------------- Page: 13 ----------------------
– 12 – IEC 60068-3-6:2018 © IEC 2018
4.7.3 Temperature/humidity stabilization

Humidity reached and maintained at the centre of the working space within the tolerance of

the chamber specification or the requirement of the relevant part of the IEC 60068-2 series.

An example is shown in Figure 6. Specified time t is minimum 30 min.
Allowable
range
IEC
Figure 6 – Example of temperature/humidity stabilization
4.7.4 Humidity fluctuation

The fluctuation during a specified interval of time at a measuring point is shown in Figure 7.

After the temperature and humidity has stabilized, the humidity at the centre of the working

space shall be measured at least 10 times at evenly spaced time intervals over a period of at

least 30 min. At the same time, temperature shall be measured in 9 points at least 10 times at

evenly spaced time intervals over a period of at least 30 min. Humidity shall be calculated

assuming a uniform humidity mixing ratio, using the humidity value at the centre and

temperature values measurement at 9 points. Measurements are actually made at a certain

sampling interval. It is not guaranteed that that data captures the fluctuation peak. For that

reason, the sample standard deviation, σ , shall be obtained from the data measured in

n – 1

each measurement point after temperature has stabilized. Values ±2σ shall be obtained in

n – 1

all 9 measurement points, and the highest value within that shall be annotated as the humidity

fluctuation.
The calculated values shall be indicated as N , N , … , N , … N (n≧10).
1 2 i n
The mean of N shall be N
ave.
The sample standard deviation,σ , shall be defined as follows.
n – 1
---------------------- Page: 14 ----------------------
IEC 60068-3-6:2018 © IEC 2018 – 13 –
Max
+2σ
n–1
+1σ
n–1
–1σ
n–1
Average humidity
Ave
n–1
Sample standard
deviation
–2σ
n–1
Min
0 5 10 15 20 25 30
Time (min)
IEC
Figure 7 – Example of humidity fluctuation
4.7.5 Humidity gradient

As shown in Figure 8, the maximum difference in average humidity in all measurement points

of the working space shall be the humidity gradient.
Humidity (% RH)
---------------------- Page: 15 ----------------------
– 14 – IEC 60068-3-6:2018 © IEC 2018
AveMax
AveMin
0 5 10 15 20 25 30
Time (min)
IEC
N : Mean highest humidity in each of 9 measurement points
AveMax
N : Mean lowest humidity in each of 9 measurement points
AveMin
Humidity gradient = N – N
AveMax AveMin
Figure 8 – Example of humidity gradient for chambers up to 2 000 l
4.7.6 Humidity variation in space

As shown in Figure 9, humidity variation in space is the difference between the mean humidity

at the centre of the working space and the mean humidity from all other measurement points.

The maximum difference between the ce
...

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