IEC GUIDE 115:2023

IEC GUIDE 115
®

Edition 3.0 2023-04
GUIDE
GUIDE


Application of measurement uncertainty 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

IEC GUIDE 115:2023-04(en-fr)

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IEC GUIDE 115

®


Edition 3.0 2023-04




GUIDE







GUIDE














Application of measurement uncertainty 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


INTERNATIONALE




ICS 17.020; 19.080 ISBN 978-2-8322-6712-7




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

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– 2 – IEC GUIDE 115:2023 © IEC 2023
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols. 6
3.1 Terms and definitions . 6
3.2 Symbols . 8
4 Application of measurement uncertainty principles. 8
4.1 General . 8
4.2 Background. 9
4.3 Measurement uncertainty principles – Application of procedures . 10
4.4 Reporting statements of conformity . 11
Annex A (informative) Measurement uncertainty calculations for product conformity
assessment testing . 12
A.1 Overview. 12
A.2 Guidance on making measurement uncertainty calculations . 12
A.2.1 General principles . 12
A.2.2 Uncertainty estimation approach . 12
A.2.3 Type A evaluation . 12
A.2.4 Type B evaluation . 12
A.2.5 Individual uncertainties . 13
A.2.6 Summary of steps when estimating uncertainty . 13
A.3 Measurement uncertainty examples . 16
A.3.1 General . 16
A.3.2 Example 1 . 16
A.3.3 Example 2 . 17
A.3.4 Example 3 . 18
A.3.5 Example 4 . 19
A.3.6 Example 5 . 20
A.3.7 Example 6 . 22
Bibliography . 24

Figure 1 – Application of simple acceptance . 10

Table A.1 – Type B uncertainties . 13
Table A.2 – Temperature rise significant influencing factors . 16
Table A.3 – Temperature rise influencing factors to the measured value . 17
Table A.4 – Temperature rise uncertainty budget . 17
Table A.5 – Input test uncertainty budget . 18
Table A.6 – Input power test uncertainty budget . 19
Table A.7 – Leakage current measurement uncertainty budget . 20
Table A.8 – Caliper gauge uncertainty budget . 21
Table A.9 – Torque measurement uncertainty budget . 22

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IEC GUIDE 115:2023 © IEC 2023 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

APPLICATION OF MEASUREMENT UNCERTAINTY TO CONFORMITY
ASSESSMENT ACTIVITIES IN THE ELECTROTECHNICAL SECTOR

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
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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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
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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
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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.
This third edition of IEC Guide 115 has been prepared, in accordance with ISO/IEC Directives,
Part 1, Annex A, by IECEE/CTL.
This third edition cancels and replaces the second edition published in 2021.
The main changes with respect to the previous edition are as follows:
a) document was rewritten to align with ISO/IEC 17025:2017;
b) content has been added to replace "accuracy method" with "simple acceptance" and added
"decision rule";
c) modified document title to state "measurement uncertainty";
d) removed statement of document applicability to only IECEE CB Scheme;
e) removed list of IEC technical committees to indicate document can be used by other
committees and industries;
f) added content for reporting statements of conformity.

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– 4 – IEC GUIDE 115:2023 © IEC 2023
The text of this Guide is based on the following documents:
Draft Report on voting
SMBNC/30/DV SMBNC/34/RV

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 Guide 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/standardsdev/publications.

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IEC GUIDE 115:2023 © IEC 2023 – 5 –
INTRODUCTION
This document 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 17025:2017 to the electrical safety testing conducted within the electrotechnical
sector.
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 document 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.
ISO/IEC 17025 was written as a general use document, for all industries. Measurement
uncertainty principles are applied to laboratory measurements and presentation of results to
provide a degree of assurance that decisions made about conformance of the products tested,
in accordance with the relevant requirements, are valid. Procedures and techniques for
measurement uncertainty calculations are well established. This document is written to provide
more specific guidance on the application of measurement uncertainty principles and applying
the decision rule to conformance statements when reporting test results.
This document is of particular interest to IEC technical committees, which can decide to make
use of it if necessary.

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– 6 – IEC GUIDE 115:2023 © IEC 2023
APPLICATION OF MEASUREMENT UNCERTAINTY TO CONFORMITY
ASSESSMENT ACTIVITIES IN THE ELECTROTECHNICAL SECTOR



1 Scope
This document presents a practical approach to the application of measurement uncertainty to
electrical safety testing conducted within 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. It describes the application of measurement uncertainty
principles.
This document provides guidance on making measurement uncertainty calculations and gives
some examples relating to measurement uncertainty calculations for product conformity
assessment testing.
NOTE The IEC Standardization Management Board (SMB) has decided that Guides such as this one can have
mandatory requirements which shall be followed by all IEC committees developing technical work that falls within the
scope of the Guide, as well as guidance which may or may not be followed. The mandatory requirements in this
Guide are identified by the use of "shall". Statements that are only for guidance are identified by using the verb
"should". (See ISO/IEC Directives, IEC Supplement:2021, A.1.1.)
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.
ISO/IEC 17025:2017, General requirements for the competence of testing and calibration
laboratories
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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
3.1.1
measurand
quantity intended to be measured
[SOURCE: ISO/IEC Guide 99:2007, 2.3, modified – NOTES and EXAMPLES have been
deleted.]

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IEC GUIDE 115:2023 © IEC 2023 – 7 –
3.1.2
measurement uncertainty
non-negative parameter characterizing the dispersion of the quantity values being attributed to
a measurand, based on the information used
[SOURCE: ISO/IEC Guide 99:2007, 2.26, modified – NOTES 1 to 4 have been deleted.]
3.1.3
decision rule
documented rule that describes how measurement uncertainty will be accounted for with regard
to accepting or rejecting an item, given a specified requirement and the result of a measurement
[SOURCE: ISO/IEC Guide 98-4:2012, 3.3.12]
3.1.4
simple acceptance
decision rule in which the producer and user of the measurement result agree, implicitly or
explicitly, to accept as conforming (and reject otherwise) an item whose property has a
measured value in the tolerance interval
Note 1 to entry: The definition is based on ISO/IEC Guide 98-4:2012, 8.2.1.
Note 2 to entry: Within the IECEE CB Scheme, the producer is the laboratory and the user is the Certification Body.
3.1.5
coverage factor
number larger than one by which a combined standard measurement uncertainty is multiplied
to obtain an expanded measurement uncertainty
Note 1 to entry: A coverage factor is usually symbolized k (see also ISO/IEC Guide 98-3:2008, 2.3.6).
[SOURCE: ISO/IEC Guide 99:2007, 2.38]
3.1.6
combined standard uncertainty
standard measurement uncertainty that is obtained using the individual standard measurement
uncertainties associated with the input quantities in a measurement model
[SOURCE: ISO/IEC Guide 99:2007, 2.31, modified – The NOTE has been deleted.]
3.1.7
measurement error
measured quantity value minus a reference quantity value
[SOURCE: ISO/IEC Guide 99:2007, 2.16, modified – NOTES 1 and 2 have been deleted.)
3.1.8
expanded measurement uncertainty
product of a combined standard measurement uncertainty and a factor larger than the number
one
Note 1 to entry: The factor depends upon the type of probability distribution of the output quantity in a measurement
model and on the selected coverage probability.
Note 2 to entry: The term "factor" in this definition refers to a coverage factor.
[SOURCE: ISO/IEC Guide 99:2007, 2.35, modified – NOTE 3 has been deleted.]

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– 8 – IEC GUIDE 115:2023 © IEC 2023
3.1.9
level of confidence
probability that the value of the measurand lies within the quoted range of measurement
uncertainty
3.1.10
standard deviation
positive square root of the variance
3.1.11
standard uncertainty
uncertainty of the result of a measurement expressed as a standard deviation
[SOURCE: ISO/IEC Guide 98-3:2008, 2.3.1]
3.1.12
Type A evaluation method
method of evaluation of measurement uncertainty by the statistical analysis of a series of
observations
3.1.13
Type B evaluation method
method of evaluation of measurement uncertainty by means other than the statistical analysis
of a series of observations (e.g. rectangular, triangular, distribution)
3.2 Symbols
X quantity input
i
x uncertainty contributor
i
4 Application of measurement uncertainty principles
4.1 General
4.1.1 Qualification and acceptance of CB test laboratories (CBTL) – for example, in the
IECEE – is performed in accordance with ISO/IEC 17025.

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IEC GUIDE 115:2023 © IEC 2023 – 9 –
ISO/IEC 17025:2017 states:
7.6 Evaluation of measurement uncertainty
7.6.1 Laboratories shall identify the contributions to measurement uncertainty. When
evaluating measurement uncertainty, all contributions that are of significance, including those
arising from sampling, shall be taken into account using appropriate methods of analysis.
7.6.2 A laboratory performing calibrations, including of its own equipment, shall evaluate
the measurement uncertainty for all calibrations.
7.6.3 A laboratory performing testing shall evaluate measurement uncertainty. Where the
test method precludes rigorous evaluation of measurement uncertainty, an estimation shall
be made based on an understanding of the theoretical principles or practical experience of
the performance of the method.
NOTE 1 In those cases where a well-recognized test method specifies limits to the values of the major sources
of measurement uncertainty and specifies the form of presentation of the calculated results, the laboratory is
considered to have satisfied 7.6.3 by following the test method and reporting instructions.
NOTE 2 For a particular method where the measurement uncertainty of the results has been established and
verified, there is no need to evaluate measurement uncertainty for each result if the laboratory can demonstrate
that the identified critical influencing factors are under control.

4.1.2 ISO/IEC 17025:2017, 7.8.3.1 states that the test report shall, where necessary for the
interpretation of the test results, include the following:
c) where applicable, the measurement uncertainty presented in the same unit as that of the
measurand or in a term relative to the measurand (e.g. percent) when:
– it is relevant to the validity or application of the test results;
– a customer's instruction so requires, or
– the measurement uncertainty affects conformity to a specification limit;

Guidance on evaluation of measurement uncertainty is given in Annex A.
4.2 Background
4.2.1 A challenge to applying measurement uncertainty principles to conformity assessment
activities is managing the cost, time and practical aspects of determining the various sources
of uncertainty. Some possible contributions are either unknown or would take considerable
effort, time and cost to establish. There are a number of proven techniques available to address
this challenge. These techniques include selecting those contributors which significantly
influence measurement uncertainty.
4.2.2 Test methods used under the IECEE Certification Body (CB) Scheme are in essence
consensus standards. Criteria used to determine conformance with requirements are most often
based on a consensus of judgment of the limits that are applicable to the test result. Exceeding
the limit by a small amount does not result in an imminent hazard. Test methods used can have
a statement expressing the maximum permissible measurement uncertainty expected to be
achieved when the method is used. Historically, and still today, test laboratories have used
state-of-the-art equipment and have not considered measurement uncertainty when comparing
test results to specification limits: the observed results were compared directly to the limits
stated in the standard. Safety standards have been developed in this environment and the
specification limits in the standards reflect this practice. This practice provides the basis for use
of the simple acceptance decision rule under the IECEE CB Scheme (see 4.3.3).

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– 10 – IEC GUIDE 115:2023 © IEC 2023
4.3 Measurement uncertainty principles – Application of procedures
4.3.1 When a test results in measurement of a variable, there is uncertainty associated with
the measured result obtained.
4.3.2 Measurement uncertainty is used for statements of conformity within the IECEE CB
Scheme in accordance with ISO/IEC 17025:2017, 7.6.1 and 7.6.3. The reporting of the
measurement uncertainty for measurements is not necessary unless the test standard or
customer requires it in accordance with ISO/IEC 17025:2017, 7.8.3.1 c).
NOTE Within the IECEE CB Scheme, the customer is understood to be the Certification Body.
4.3.3 When comparing the obtained measurement results with the applicable limits in
accordance with the specification in the IEC standards, the conformance decision is made
without applying the measurement uncertainty. Refer to Figure 1. This is often called "simple
acceptance" (see ISO/IEC Guide 98-4:2012, 8.3.1.2).
4.3.4 Simple acceptance anticipates the agreement of an acceptable level of measurement
uncertainty when applying the decision rule. For this purpose, the contributors to measurement
uncertainty can be limited to those related to the measuring equipment as noted below. Other
contributors can be considered by the laboratory.
a) Equipment accuracy: Meets the requirements of the test standard or, where not stated in
the test standard, the default values given in IECEE OD-5014.
b) Control of environment: Ambient temperature, humidity, power quality, etc. for use of the
measurement equipment are controlled. These are not considered as significant contributors
if they are within the equipment manufacturer's specifications for the stated accuracy
specification.
c) Resolution: It is not considered to be a significant contributor for conformance decision
purposes if it is the same, or better, than the least significant digit of the test method
specification or the conformance criteria provided by the test standard.

Figure 1 – Application of simple acceptance

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IEC GUIDE 115:2023 © IEC 2023 – 11 –
4.4 Reporting statements of conformity
In order to fulfil the requirement of ISO/IEC 17025:2017, 7.8.6.1, the test report should contain
a general statement such as: "Measurement uncertainty is not applied when providing
statements of conformity in accordance with IEC Guide 115:2023, 4.3.3."

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– 12 – IEC GUIDE 115:2023 © IEC 2023
Annex A
(informative)

Measurement uncertainty calculations for
product conformity assessment testing
A.1 Overview
This Annex A is meant to be a short and simplified summary of the steps to be taken by a
CB test laboratory (CBTL) when the need to estimate measurement uncertainties arises. It also
includes examples of how to perform the calculations. It is by no means a comprehensive
document about measurement uncertainty, the sources and estimation of measurement
uncertain
...