IEC GUIDE 115:2007

IEC GUIDE 115
Edition 1.0 2007-09
GUIDE 115
GUIDE 115
Application of uncertainty of measurement to conformity assessment activities
in the electrotechnical sector

Application de l’incertitude de mesure aux activités d’évaluation de la
conformité dans le secteur électrotechnique
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or
IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: 0Hinmail@iec.ch
Web: 1Hwww.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: 2Hwww.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: 3Hwww.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
ƒ Electropedia: 4Hwww.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
ƒ Customer Service Centre: 5Hwww.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: 6Hcsc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.
ƒ Catalogue des publications de la CEI: 7Hwww.iec.ch/searchpub/cur_fut-f.htm
Le Catalogue en-ligne de la CEI vous permet d’effectuer des recherches en utilisant différents critères (numéro de référence,
texte, comité d’études,…). Il donne aussi des informations sur les projets et les publications retirées ou remplacées.
ƒ Just Published CEI: 8Hwww.iec.ch/online_news/justpub
Restez informé sur les nouvelles publications de la CEI. Just Published détaille deux fois par mois les nouvelles
publications parues. Disponible en-ligne et aussi par email.
ƒ Electropedia: 9Hwww.electropedia.org
Le premier dictionnaire en ligne au monde de termes électroniques et électriques. Il contient plus de 20 000 termes et
définitions en anglais et en français, ainsi que les termes équivalents dans les langues additionnelles. Egalement appelé
Vocabulaire Electrotechnique International en ligne.
ƒ Service Clients: 10Hwww.iec.ch/webstore/custserv/custserv_entry-f.htm
Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions, visitez le FAQ du
Service clients ou contactez-nous:
Email: 11Hcsc@iec.ch
Tél.: +41 22 919 02 11
Fax: +41 22 919 03 00
IEC GUIDE 115
Edition 1.0 2007-09
GUIDE 115
GUIDE 115
Application of uncertainty of measurement to conformity assessment activities
in the electrotechnical sector

Application de l’incertitude de mesure aux activités d’évaluation de la
conformité dans le secteur électrotechnique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
T
CODE PRIX
ICS 17.020; 19.080 ISBN 2-8318-9307-0

– 2 – Guide 115 © IEC:2007
CONTENTS
FOREWORD.03
INTRODUCTION.5H1H4

1 Scope.6H2H5
2 Reference documents.7H3H5
3 Terms and definitions .8H4H5
4 Application of uncertainty of measurement principles .9H5H6
4.1 General .10H6H6
4.2 Uncertainty of measurement principles.11H7H7
4.3 Background .12H8H7
4.4 Uncertainty of measurement principles – Application of procedures .13H9H8
4.5 Conclusion .14H10H10
5 Guidance on making uncertainty of measurement calculations including examples
of how to perform the calculations .15H11H10
5.1 General principles .16H12H10
5.2 Summary of steps when estimating uncertainty .17H13H11
5.3 Simple example – Estimation of measurement uncertainty for a temperature-
rise test with thermocouples .18H14H14

Annex A (informative) Uncertainty of measurement calculations for product
conformity assessment testing – Examples 1 to 6 .19H15H16

Guide 115 © IEC:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
APPLICATION OF UNCERTAINTY OF MEASUREMENT
TO CONFORMITY ASSESSMENT ACTIVITIES
IN THE ELECTROTECHNICAL SECTOR

FOREWORD
This first edition of IEC Guide 115 has been prepared in accordance with Annex A of Part 1 of
the ISO/IEC Directives by the IECEE/CTL.
The text of this guide is based on the following documents:
Approval document Report on voting
C/1446/DV C/1457/RV
Full information on the voting for the approval of this Guide can be found in the report on
voting indicated in the above table.

– 4 – Guide 115 © IEC:2007
INTRODUCTION
This Guide has been prepared by the IECEE Committee of Testing Laboratories (CTL) to
provide guidance on the practical application of the measurement uncertainty requirements of
ISO/IEC 17025 to the electrical safety testing conducted within the IECEE CB Scheme.
The IECEE CB Scheme is a multilateral, international agreement, among over 40 countries
and some 60 national certification bodies, for the acceptance of test reports on electrical
products tested to IEC standards.
The aim of the CTL is, among other tasks, to define a common understanding of the test
methodology with regard to the IEC standards as well as to ensure and continually improve
the repeatability and reproducibility of test results among the member laboratories.
The practical approach to measurement uncertainty outlined in this Guide has been adopted
for use in the IECEE Schemes, and is also extensively used around the world by testing
laboratories engaged in testing electrical products to national safety standards.
This guide is of particular interest to the following IEC Technical Committees which may
decide to make use of it if necessary:
TECHNICAL COMMITTEE 13: EQUIPMENT FOR ELECTRICAL ENERGY MEASUREMENT, TARIFF
AND LOAD CONTROL
TECHNICAL COMMITTEE 17: SWITCHGEAR AND CONTROLGEAR
TECHNICAL COMMITTEE 18: ELECTRICAL INSTALLATIONS OF SHIPS AND OF MOBILE
AND FIXED OFFSHORE UNITS
TECHNICAL COMMITTEE 20: ELECTRIC CABLES
TECHNICAL COMMITTEE 21: SECONDARY CELLS AND BATTERIES
TECHNICAL COMMITTEE 22: POWER ELECTRONIC SYSTEMS AND EQUIPMENT
TECHNICAL COMMITTEE 23: ELECTRICAL ACCESSORIES
TECHNICAL COMMITTEE 32: FUSES
TECHNICAL COMMITTEE 33: POWER CAPACITORS
TECHNICAL COMMITTEE 34: LAMPS AND RELATED EQUIPMENT
TECHNICAL COMMITTEE 35: PRIMARY CELLS AND BATTERIES
TECHNICAL COMMITTEE 38: INSTRUMENT TRANSFORMERS
TECHNICAL COMMITTEE 39: ELECTRONIC TUBES
TECHNICAL COMMITTEE 40: CAPACITORS AND RESISTORS FOR ELECTRONIC
EQUIPMENT
TECHNICAL COMMITTEE 47: SEMICONDUCTOR DEVICES
TECHNICAL COMMITTEE 59: PERFORMANCE OF HOUSEHOLD ELECTRICAL
APPLIANCES
TECHNICAL COMMITTEE 61: SAFETY OF HOUSEHOLD AND SIMILAR ELECTRICAL
APPLIANCES
TECHNICAL COMMITTEE 62: ELECTRICAL EQUIPMENT IN MEDICAL PRACTICE
TECHNICAL COMMITTEE 64: ELECTRICAL INSTALLATIONS AND PROTECTION
AGAINST ELECTRIC SHOCK
TECHNICAL COMMITTEE 65: INDUSTRIAL-PROCESS MEASUREMENT AND CONTROL
TECHNICAL COMMITTEE 66: SAFETY OF MEASURING, CONTROL AND LABORATORY
EQUIPMENT
TECHNICAL COMMITTEE 76: OPTICAL RADIATION SAFETY AND LASER EQUIPMENT
TECHNICAL COMMITTEE 77: ELECTROMAGNETIC COMPATIBILITY
TECHNICAL COMMITTEE 78: LIVE WORKING
TECHNICAL COMMITTEE 80: MARITIME NAVIGATION AND RADIOCOMMUNICATION
EQUIPMENT AND SYSTEMS
TECHNICAL COMMITTEE 82: SOLAR PHOTOVOLTAIC ENERGY SYSTEMS

Guide 115 © IEC:2007 – 5 –
APPLICATION OF UNCERTAINTY OF MEASUREMENT
TO CONFORMITY ASSESSMENT ACTIVITIES
IN THE ELECTROTECHNICAL SECTOR

1 Scope
This Guide presents a practical approach to the application of uncertainty of measurement to
conformity assessment activities in the electrotechnical sector . It is specifically conceived for
use in IECEE Schemes as well as by testing laboratories engaged in testing electrical
products to national safety standards. Clause 4 describes the application of uncertainty of
measurements principles. Clause 5 provides guidance on making uncertainty of measurement
calculations. Annex A gives some examples relating to uncertainty of measurement
calculations for product conformity assessment testing.
2 Reference documents
ISO/IEC 17025: General requirements for the competence of testing and calibration
laboratories
Guide to the expression of uncertainty in measurement (GUM) (1995)
[BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML]
International vocabulary of basic and general terms in metrology (VIM) (1996)
[BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML]
3 Terms and definitions
For the purposes of this Guide, the following terms and definitions apply.
3.1
coverage factor
number that, when multiplied by the combined standard uncertainty, produces an interval (the
expanded uncertainty) about the measurement result that may be expected to encompass a
large, specified fraction (e.g. 95 %) of the distribution of values that could be reasonably
attributed to the measurand
3.2
combined standard uncertainty
result of the combination of standard uncertainty components
3.3
error of measurement
result of a measurement minus a true value of the measurand (not precisely quantifiable
because true value lies somewhere unknown within the range of uncertainty)
3.4
expanded uncertainty
obtained by multiplying the combined standard uncertainty by a coverage factor
3.5
level of confidence
probability that the value of the measurand lies within the quoted range of uncertainty

– 6 – Guide 115 © IEC:2007
3.6
measurand
quantity subjected to measurement, evaluated in the state assumed by the measured system
during the measurement itself
[IEC 60359:2001]
3.7
quantity X
i
source of uncertainty
3.8
standard deviation
positive square root of the variance
3.9
standard uncertainty
estimated standard deviation
3.10
uncertainty (of measurement)
parameter, associated with the result of a measurement, that characterizes the dispersion of
the values that could reasonably be attributed to the measurand
[IEC 60359:2001, modified]
3.11
type A evaluation method
method of evaluation of uncertainty of measurement by the statistical analysis of series of
observations
3.12
type B evaluation method
method of evaluation of uncertainty of measurement by means other than the statistical
analysis of series of observations
4 Application of uncertainty of measurement principles
4.1 General
4.1.1 Qualification and acceptance of CB test laboratories (CBTL), e.g. in the IECEE, is
performed according to IEC/ISO 17025, which states in 5.4.6.2:
“Testing laboratories shall have and apply procedures for estimating uncertainty of measure-
ment. In certain cases, the nature of the test method may preclude rigourous, metrologically
and statistically valid, calculation of uncertainty of measurement. In these cases the
laboratory shall at least attempt to identify all the components of uncertainty and make a
reasonable estimation, and shall ensure that the form of reporting of the result does not give a
wrong impression of the uncertainty. Reaso
...