IEC 61124:2023

IEC 61124 ®
Edition 4.0 2023-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Reliability testing – Compliance tests for constant failure rate and constant
failure intensity
Essais de fiabilité – Plans d’essai de conformité pour un taux de défaillance
constant et une intensité de défaillance constante

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 l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
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 corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always have
committee, …). It also gives information on projects, replaced access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 19 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or need
further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) 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 IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - Découvrez notre puissant moteur de recherche et consultez
webstore.iec.ch/advsearchform gratuitement tous les aperçus des publications. Avec un
La recherche avancée permet de trouver des publications IEC abonnement, vous aurez toujours accès à un contenu à jour
en utilisant différents critères (numéro de référence, texte, adapté à vos besoins.
comité d’études, …). Elle donne aussi des informations sur les
projets et les publications remplacées ou retirées. Electropedia - www.electropedia.org

Le premier dictionnaire d'électrotechnologie en ligne au monde,
IEC Just Published - webstore.iec.ch/justpublished
avec plus de 22 300 articles terminologiques en anglais et en
Restez informé sur les nouvelles publications IEC. Just
français, ainsi que les termes équivalents dans 19 langues
Published détaille les nouvelles publications parues.
additionnelles. Egalement appelé Vocabulaire
Disponible en ligne et une fois par mois par email.
Electrotechnique International (IEV) en ligne.

Service Clients - webstore.iec.ch/csc
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
IEC Products & Services Portal - products.iec.ch

IEC 61124 ®
Edition 4.0 2023-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Reliability testing – Compliance tests for constant failure rate and constant

failure intensity
Essais de fiabilité – Plans d’essai de conformité pour un taux de défaillance

constant et une intensité de défaillance constante

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 03.120.30; 19.020; 21.020 ISBN 978-2-8322-6453-9

– 2 – IEC 61124:2023 © IEC 2023
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references . 10
3 Terms, definitions, abbreviated terms and symbols . 11
3.1 Terms and definitions . 11
3.2 Abbreviated terms and symbols . 11
3.2.1 Abbreviated terms . 11
3.2.2 Symbols . 11
4 General requirements and area of application . 13
4.1 Requirements and characteristics . 13
4.2 Applicability to replaced and repaired items . 13
4.3 Types of test plans . 14
4.3.1 General . 14
4.3.2 Advantages and disadvantages of the different test plan types . 14
5 General test procedure . 16
5.1 Test conditions . 16
5.2 General characteristics of the test plans . 17
5.3 Data to be recorded . 17
*
5.4 Calculation of accumulated test time, T . 17
5.5 Number of failures . 18
6 Truncated sequential probability ratio test (SPRT) plans . 18
6.1 General . 18
6.2 Common test procedure . 19
6.3 Decision criteria . 19
6.4 Operating characteristic (OC) curve . 20
6.5 Expected accumulated test time to decision (ETT) . 21
6.6 Overview of test plans . 22
7 Fixed time/failure terminated test plans – Fixed duration (to acceptance) test
plans . 25
7.1 General . 25
7.2 Common test procedure . 26
7.3 Decision criteria . 26
7.4 Test plans . 26
8 Design of alternative time/failure terminated test plans (FTFT) . 27
8.1 General . 27
8.2 Design procedures . 27
8.3 Common FTFT procedure . 28
8.4 Decision criteria . 28
9 Calendar time/failure terminated test plans (FTFT) for non-replaced items . 28
9.1 General . 28
9.2 Common test procedure . 29
9.3 Decision criteria . 29
9.4 Use of IEC 61123:2019, Table 5 for fixed calendar time tests . 29
9.4.1 General . 29
9.4.2 Procedure when the test time is given . 30

9.4.3 Procedure when the number of items is given . 30
10 Combined test plans . 30
10.1 General . 30
10.2 Common test procedure . 30
10.3 Decision criteria . 31
10.4 Test plans . 31
11 Performing the test and presenting the results . 32
Annex A (normative) Tables for border lines of SPRT plans (types A and C) . 33
A.1 Symbols . 33
A.2 Border lines . 33
A.3 Example of the SPRT plan from Clause 6 . 37
Annex B (normative) Tables and graphs for combined test plans (type D) . 39
B.1 General . 39
B.2 Test plans D.3 and C.3 (α = β = 10 %, D = 1,7 ) . 41
Annex C (informative) Extension of the set of SPRTs type A . 44
C.1 Symbols . 44
C.2 Extension of the set of type A tests (through interpolation by α and β ) . 44
Annex D (informative) Approximation of operating characteristic for type A SPRTs by
Wald's formula . 47
D.1 Symbols . 47
D.2 Approximations of OC in this document . 47
D.3 Approximation of OC for type A SPRT by Wald's formula . 47
D.4 Construction of the approximated OC curve using a spreadsheet . 49
Annex E (informative) Mathematical references and examples for fixed time/failure
terminated test (FTFT) plans . 51
E.1 Symbols . 51
E.2 Mathematical references . 51
E.2.1 General .
...