IEC 60068-3-11:2007

Environmental testing - Part 3-11: Supporting documentation and guidance - Calculation of uncertainty of conditions in climatic test chambers

Demonstrates how to estimate the uncertainty of steady-state temperature and humidity conditions in temperature and humidity chambers. Since this is inextricably linked to the methods of measurement, these are also described. This standard is equally applicable to all environmental enclosures, including rooms or laboratories. The methods used apply both to temperature chambers and combined temperature and humidity chambers. This standard is meant to help everyone using climatic test chambers. Those already familiar with uncertainty of measurement will find it useful for guidance on typical sources of uncertainty and how they should be quantified and combined. It is also intended to assist the first-time or occasional user who has little or no knowledge of the subject. To discuss uncertainty, it is important first to understand what is being measured or characterized. The calibration or characterization of the performance of a chamber is concerned with the humidity and temperature of the air in the chamber, as experienced by the item under test, at a given set point. This should not be confused with characterizing or calibrating the chamber sensor, which is a separate matter.

Essais d'environnement - Partie 3-11: Documentation d'accompagnement et guide - Calcul de l'incertitude des conditions en chambres d'essais climatiques

Montre comment estimer l'incertitude des conditions de température et d'humidité à l'état stable dans une chambre d'essais de température et d'humidité. Sachant que cela est inextricablement lié aux méthodes de mesures, celles-ci sont également décrites. La présente norme est également applicable à tout type d'enceintes d'environnement, et même les salles ou laboratoires. Les méthodes sont usuellement appliquées aux chambres d'essais régulées en température et aux chambres d'essais régulées en température et humidité. La présente norme cherche à aider toute personne utilisant des chambres d'essais climatiques. Les personnes étant déjà familières avec l'incertitude de mesure la trouveront utile pour les conseils sur les composantes types d'incertitudes et sur la manière dont il convient de les quantifier et de les combiner. Elle est également destinée à aider le nouvel utilisateur ou l'utilisateur occasionnel qui n'a qu'une faible connaissance du sujet ou pas de connaissance du tout. Afin d'aborder les incertitudes il est important tout d'abord de comprendre ce qui est mesuré ou caractérisé. L'étalonnage ou la caractérisation de la performance d'une chambre d'essais fait appel à la détermination de l'humidité et de la température de l'air de la chambre, vu par l'objet en essai, à une valeur de consigne donnée. Il convient que cela ne soit pas confondu avec le calibrage ou l'étalonnage du capteur de la chambre d'essai, qui est une opération différente.

General Information

• Status: Published
• Publication Date: 14-May-2007
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 19.040 - Environmental testing
• Technical Committee: TC 104 - Environmental conditions, classification and methods of test
• Drafting Committee: MT 18 - TC 104/MT 18
• Current Stage: PPUB - Publication issued
• Start Date: 15-Jul-2007
• Completion Date: 15-May-2007

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
CEI
60068-3-11
NORME
First edition
INTERNATIONALE
Première édition
2007-05
Environmental testing –
Part 3-11:
Supporting documentation and guidance –
Calculation of uncertainty of conditions
in climatic test chambers
Essais d’environnement –
Partie 3-11:
Documentation d’accompagnement et guide –
Calcul de l’incertitude des conditions
en chambres d’essais climatiques
Reference number
Numéro de référence
IEC/CEI 60068-3-11:2007
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INTERNATIONAL IEC
STANDARD
CEI
60068-3-11
NORME
First edition
INTERNATIONALE
Première édition
2007-05
Environmental testing –
Part 3-11:
Supporting documentation and guidance –
Calculation of uncertainty of conditions
in climatic test chambers
Essais d’environnement –
Partie 3-11:
Documentation d’accompagnement et guide –
Calcul de l’incertitude des conditions
en chambres d’essais climatiques
PRICE CODE
V
CODE PRIX
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – 60068-3-11 © IEC:2007
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 Concept of uncertainty.11
4.1 Uncertainty, error and “true value”.11
4.2 Statements of uncertainty.12
4.3 Combining uncertainties .13
5 Tolerance .13
6 Humidity and temperature measurement .13
7 Methods for determining climatic test chamber uncertainties .14
7.1 Empty chamber .16
7.2 Typical load.16
7.3 Measurement of conditions in the chamber during the test .17
7.4 Conditions to measure.17
7.5 Measurements required.18
7.6 Sources of uncertainty.19
7.7 Essential contributions of uncertainty .20
8 Estimation of uncertainty components and their combination .24
9 Overall uncertainty of temperature measurement.24
9.1 General .24
9.2 Further considerations.26
10 Overall uncertainty of relative humidity measurement .26
10.1 Uncertainty of temperature measurement at each sensor point.27
10.2 Uncertainty of the relative humidity measurement.27
11 Anomalous data and presentation of results .30
11.1 Average case analysis.30
11.2 Worst case analysis .30

Annex A (informative) Measurement data sets – Loaded chamber .32

Bibliography.34

60068-3-11 © IEC:2007 – 3 –
Figure 1 – Approaches to calibration method and uncertainty calculation.15
Figure 2 – Illustration of the fluctuation of a temperature sensor .23

Table 1 – Combination of temperature uncertainties .24
Table 2 – Combination of temperature uncertainties at each point .27
Table 3 – Combination of humidity uncertainties .28
Table A.1 – Typical temperature measurement data set and it’s analysis and refs .32
Table A.2 – Humidity measurements analysis based on Table A.1 temperatures.33

– 4 – 60068-3-11 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 3-11: Supporting documentation and guidance –
Calculation of uncertainty of conditions in climatic test chambers

FOREWORD
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International Standard IEC 60068-3-11 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
The text of this standard is based on the following documents:
FDIS Report on voting
104/409/FDIS 104/415/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

60068-3-11 © IEC:2007 – 5 –
A list of all parts in the IEC 60068 series, under the general title Environmental testing can be
found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 60068-3-11 © IEC:2007
INTRODUCTION
This part of IEC 60068 provides guidance for analysing uncertainties of temperature and
humidity in climatic test chambers. It has been written for technicians, engineers and
managers in environmental testing, and for anyone who needs to understand the results of
environmental tests.
The performance of climatic test chambers is a key concern in environmental test engineer-
ing. To comply with any test specification, the performance of the chamber needs to be
characterized to decide whether the generated conditions fall within the specified limits. This
characterization can be a difficult task, and the analysis of uncertainties in chamber
performance is often surrounded by confusion. This pu
...