CISPR TR 16-4-1:2003

TECHNICAL CISPR
REPORT 16-4-1
First edition
2003-11
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
Specification for radio disturbance and immunity
measuring apparatus and methods –

Part 4-1:
Uncertainties, statistics and limit modelling –
Uncertainties in standardized EMC tests

Reference number
CISPR 16-4-1/TR:2003(E)
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TECHNICAL CISPR
REPORT 16-4-1
First edition
2003-11
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
Specification for radio disturbance and immunity
measuring apparatus and methods –

Part 4-1:
Uncertainties, statistics and limit modelling –
Uncertainties in standardized EMC tests

© IEC 2003 ⎯ Copyright - all rights reserved
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For price, see current catalogue

– 2 – CISPR 16-4-1/TR © IEC:2003(E)

CONTENTS
FOREWORD.3

INTRODUCTION.5

TABLE RECAPITULATING CROSS-REFERENCES .8

1 General.9

1.1 Scope.9

1.2 Structure of clauses related to standards compliance uncertainties .9
2 Normative references.10
3 Terms and definitions .11
4 Basic considerations on uncertainties in emission measurements.14
4.1 Introduction.14
4.2 Types of uncertainties in emission measurements .15
4.3 Relation between standards compliance uncertainty and interference
probability .23
4.4 Assessment of uncertainties in a standardized emission measurement .25
4.5 Verification of the uncertainty budget .29
4.6 Reporting of the uncertainty .33
4.7 Application of uncertainties in the compliance criterion.35
5 Basic considerations on uncertainties in immunity testing.38
6 Voltage measurements.38
6.1 Introduction.38
6.2 Voltage measurements (general).38
6.3 Voltage measurements using a voltage probe .42
6.4 Voltage measurement using a V-terminal Artificial Mains Network .43
6.5 Bibliography.50
7 Absorbing clamp measurements .57
8 Radiated emission measurements .57
9 Conducted immunity measurements .57
10 Radiated immunity measurements .57

Annex A (informative) Compliance uncertainty and interference probability.58

A.1 Introduction.58
A.2 Application to radiated emissions, an example .58
A.3 Reducing the compliance uncertainty .59
Annex B (informative) Analysis method of results of an inter-laboratory test .60

Bibliography.61

CISPR 16-4-1/TR © IEC:2003(E) – 3 –

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
SPECIFICATION FOR RADIO DISTURBANCE AND IMMUNITY

MEASURING APPARATUS AND METHODS –

Part 4-1: Uncertainties, statistics and limit modelling –

Uncertainties in standardized EMC tests

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
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
CISPR 16-4-1, which is a technical report, has been prepared by CISPR subcommittee A:
Radio interference measurements and statistical methods.
This first edition of CISPR 16-4-1, together with CISPR 16-4-3, CISPR 16-4-4 and the second
edition of CISPR 16-3, cancels and replaces the first edition of CISPR 16-3, published in
2000, and its amendment 1 (2002). It contains the relevant clauses of CISPR 16-3 without
technical changes.
– 4 – CISPR 16-4-1/TR © IEC:2003(E)

The text of this technical report is based on the first edition of CISPR 16-3 and on the
following documents:
Enquiry draft Report on voting

CISPR/A/450/DTR CISPR/A/466/RVC

Full information on the voting for the approval of this technical report 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.

A bilingual version of this publication may be issued at a later date.
The committee has decided that the contents of this publication will remain unchanged until
2004. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
CISPR 16-4-1/TR © IEC:2003(E) – 5 –

INTRODUCTION
CISPR 16-1, CISPR 16-2, CISPR 16-3 and CISPR 16-4 have been reorganised into 14 parts,

to accommodate growth and easier maintenance. The new parts have also been renumbered.

See the list given below.
Old CISPR 16 publications New CISPR 16 publications

CISPR 16-1-1 Measuring apparatus

CISPR 16-1-2 Ancillary equipment – Conducted disturbances
Radio disturbance
and immunity
CISPR 16-1-3 Ancillary equipment – Disturbance power

CISPR 16-1
measuring
apparatus
Ancillary equipment – Radiated disturbances
CISPR 16-1-4
Antenna calibration test sites for 30 MHz to
CISPR 16-1-5
1 000 MHz
CISPR 16-2-1 Conducted disturbance measurements
Methods of
Measurement of disturbance power
CISPR 16-2-2
measurement of
CISPR 16-2
disturbances and
CISPR 16-2-3 Radiated disturbance measurements
immunity
CISPR 16-2-4
Immunity measurements
CISPR 16-3 CISPR technical reports
Uncertainties in standardised EMC tests
CISPR 16-4-1
Reports and
Measurement instrumentation uncertainty
CISPR 16-3 recommendations CISPR 16-4-2
of CISPR
Statistical considerations in the
CISPR 16-4-3
determination of EMC compliance of mass-
produced products
Statistics of complaints and a model for the
Uncertainty in EMC
CISPR 16-4 CISPR 16-4-4
calculation of limits
measurements
More specific information on the relation between the ‘old’ CISPR 16-3 and the present ‘new’
CISPR 16-4-1 is given in the table after this introduction (TABLE RECAPITULATING CROSS
REFERENCES).
Measurement instrumentation specifications are given in five new parts of CISPR 16-1, while
the methods of measurement are covered now in four new parts of CISPR 16-2. Various
reports with further information and background on CISPR and radio disturbances in general
are given in CISPR 16-3. CISPR 16-4 contains information related to uncertainties, statistics
and limit modelling.
CISPR 16-4 consists of the following parts, under the general title Specification for radio
disturbance and immunity measuring apparatus and methods - Uncertainties, statistics and

limit modelling:
• Part 4-1: Uncertainties in standardised EMC tests,
• Part 4-2: Uncertainty in EMC measurements,
• Part 4-3: Statistical considerations in the determination of EMC compliance of mass-
produced products,
• Part 4-4: Statistics of complaints and a model for the calculation of limits.
For practical reasons, standardised EMC tests are drastic simplifications of all possible EMI
scenarios that a product may encounter in practice. Consequently, in an EMC standard the
measurand, the limit, measurement instruments, set-up, measurement procedure and
measurement conditions shall be simplified but still meaningful. Meaningful means that there
is a statistical correlation between compliance of the product with a standardized EMC test
and a high probability of actual EMC of the same product during its life cycle. Part 4-4
provides statistical based methods to derive meaningful disturbance limits to protect the radio
services.
– 6 – CISPR 16-4-1/TR © IEC:2003(E)

In general, a standardized EMC test must be developed such that reproducible results are

obtained if different parties perform the same test with the same product. However, various

uncertainty sources and influence quantities cause that the reproducibility of a standardized

EMC test is limited. Part 4-1 consists of a collection of informative reports that deal with all

relevant uncertainty sources that may be encountered during EMC compliance tests. Typical

examples of uncertainty sources are the product itself, the measurement instrumentation, the

set-up of the product, the test procedures and the environmental conditions.

Part 4-2, deals with a limited and specific category of uncertainties (i.e. the measurement

instrumentation uncertainties). In Part 4-2, examples of measurement instrumentation
uncertainty budgets are given for most of the CISPR test methods. In this part also

requirements are given on how to incorporate the measurement instrumentation uncertainty in

the compliance criterion.
If a compliance test is performed using different samples of the same product, then the
spread of the EMC performance of the product samples shall be incorporated also in the
compliance criterion. Part 4-3 deals with the statistical treatment of test results in case
compliance test are performed using samples of mass-produced products. This treatment is
well known as the 80 %-80 % rule.
Many important decisions are based on the results of EMC tests. The results are used, for
example, to judge compliance against specifications or statutory requirements. Whenever
decisions are based on EMC tests, it is important to have some indication of the quality of the
results, that is, the extent to which they can be relied on for the purpose in hand. Confidence
in test results obtained outside the user’s own organisation is a prerequisite to meeting this
objective. In the sector of EMC it is often times a formal (frequently legislative) requirement
for test laboratories to introduce quality assurance measures to ensure that they are capable
of and are providing results of the required quality. Such measures include: the valid use of
standardized test methods; the use of defined internal quality control procedures; participation
in proficiency testing schemes; accreditation to ISO 17025; and establishing traceability of the
results of the tests.
As a consequence of these requirements, EMC test laboratories are, for their part, coming
under increasing pressure to demonstrate the quality of their test results. This includes the
degree to which a test result would be expected to agree with other test results
(reproducibility using the same test method), normally irrespective of the methods used
(reproducibility using alternative test methods). A useful means to demonstrate the quality of
standardized EMC tests is the evaluation of the associated uncertainty.
Although the concept of measurement uncertainty has been recognised by EMC specialists
for many years, it was the publication of the ‘Guide to the Expression of Uncertainty in
Measurement’ (the GUM) by ISO in 1993, and the publication of the EMC specific NAMAS
publication NIS 81 on ‘The treatment of Uncertainty in EMC measurements’ in 1994, which

established general and EMC specific rules for evaluating and expressing uncertainty of EMC
measurements.
In contrast to classical metrology problems, in EMC there has been great emphasis on
precision of results obtained using a specified and standardized method, rather than on their
traceability to a defined standard or SI unit. This has led to the use of standardized test
methods, such as the CISPR standards, to fulfil legislative and trading requirements.
Furthermore, in EMC tests the magnitude of the intrinsic uncertainty (mainly due to
reproducibility problems of the set-up of products and their cabling) is large compared to the
uncertainties induced by the measurement instrumentation and test procedure. These two
important differences between EMC test methods and classical metrology tests, makes it
necessary to give specific guidance for evaluating uncertainties of EMC tests, in addition to
the generic uncertainty guides like the aforementioned ISO Guide (GUM) on measurement
uncertainties.
CISPR 16-4-1/TR © IEC:2003(E) – 7 –

CISPR 16-4-1 consists of a collection of informative reports that deal with all relevant

uncertainty sources that may be encountered during EMC compliance tests. Typical examples

of uncertainty sources are the product itself, the measurement instrumentation, the product

set-up, the test procedures and the environmental conditions. This CISPR document shows

how the concepts given in the ISO Guide may be applied in standardised EMC tests. The

EMC-specific basic uncertainty aspects of both emission and immunity tests are outlined in

Clauses 4 and 5 respectively. These basic concepts include the introduction of the different
types of uncertainties relevant in EMC tests and also the various typical categories of

uncertainty sources encountered. This is followed by a description of the steps involved in the

evaluation and application of uncertainties in EMC tests.

– 8 – CISPR 16-4-1/TR © IEC:2003(E)

TABLE RECAPITULATING CROSS-REFERENCES

First edition of CISPR 16-4-1 First edition of CISPR 16-3
Clauses Clauses
1 1 (of document CISPR/A/450/DTR)

2 2 (of document CISPR/A/450/DTR)

3 3 (of document CISPR/A/450/DTR)

4 4 (of document CISPR/A/450/DTR)
5 Reserved
6 6.3
7 Reserved
8 Reserved
9 Reserved
10 Reserved
Annexes Annexes
A A (of document CISPR/A/450/DTR)
B B (of document CISPR/A/450/DTR)

CISPR 16-4-1/TR © IEC:2003(E) – 9 –

SPECIFICATION FOR RADIO DISTURBANCE AND IMMUNITY

MEASURING APPARATUS AND METHODS –

Part 4-1: Uncertainties, statistics and limit modelling –

Uncertainties in standardized EMC tests

1 General
1.1 Scope
This part of CISPR 16-4 gives guidance on the treatment of uncertainties to those who are
involved in the development or modification of CISPR electromagnetic compatibility (EMC)
standards. In addition, this part provides useful background information for those who apply
the standards and the uncertainty aspects in practice.
The objectives of this part are:
a) to identify the parameters or sources governing the uncertainty associated with the
statement that a given product complies with the requirement specified in a
CISPR recommendation. This uncertainty will be called ‘standards compliance uncertainty’
(abbreviated as SCU, see 3.16);
b) to give guidance on the estimation of the magnitude of the standards compliance
uncertainty;
c) to give guidance for the implementation of the standards compliance uncertainty into the
compliance criterion of a CISPR standardised compliance test.
As such, this part can be considered as a handbook that can be used by standards writers to
incorporate and harmonise uncertainty considerations in existing and future CISPR standards.
This part also gives guidance to regulatory authorities, accreditation bodies and test
engineers to judge the performance quality of an EMC test-laboratory carrying out
CISPR standardised compliance tests. The uncertainty considerations given in this part can
also be used as guidance when comparing test results (and its uncertainties) obtained by
using different alternative test methods.
The uncertainty of a compliance test also relates to the probability of occurrence of an
electromagnetic interference (EMI) problem in practice. This aspect is recognized and
introduced briefly in this part. However, the problem of relating uncertainties of a compliance
test to the occurrence of EMI in practice is not considered within the scope of this part.

The scope of this part is limited to all the relevant uncertainty considerations of a
standardized EMC compliance test.
1.2 Structure of clauses related to standards compliance uncertainties
The result of the application of basic considerations (Clauses 4 and 5) in this part to existing
or new CISPR standards will lead to proposals to improve and harmonise the uncertainty
aspects of those CISPR standards. Such proposals will also be published as a report within
this part and will give the background and rationale for improvement of certain
CISPR standards. Clause 6 is an example of such a report.
The structure of clauses related to the CISPR standards compliance uncertainty work is
depicted in Table 1. Clause 3 deals with the basic considerations of standards compliance
uncertainties in emission measurements. Clause 6 contains the uncertainty considerations

– 10 – CISPR 16-4-1/TR © IEC:2003(E)

related to voltage measurements. Clauses 7 and 8 are reserved for SCU considerations of

absorbing clamp and radiated emission measurements, respectively.

Uncertainty work is also considered for immunity compliance tests in the future. Clauses 5, 9

and 10 are reserved for this material. SCU considerations of immunity tests differ from the

emission SCU considerations in particular points. For instance, in an immunity test, the

measurand is often a functional attribute of the EUT and not an isolated quantity. This may

cause additional specific SCU considerations. Priority is given to the uncertainty evaluations

for emission measurements at this stage of the work.

Table 1 – Structure of clauses related to the subject of standards compliance

uncertainty
STANDARDS COMPLIANCE UNCERTAINTY
Clause 1, 2 and 3: General
EMISSION IMMUNITY
Clause 4 Basic considerations Clause 5 Basic considerations
Clause 6 Voltage measurements Clause 9 Conducted immunity tests
Clause 7 Absorbing clamp measurements Clause 10 Radiated immunity tests
Clause 8 Radiated emission measurements

2 Normative references
The following referenced documents are indispensable for the application 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 60050-161:1990, International Electrotechnical Vocabulary (IEV) – Chapter 161:
Electromagnetic Compatibility
Amendment 1 (1997)
Amendment 2 (1998)
IEC 60050-300:2001, International Electrotechnical Vocabulary (IEV) – Electrical and
electronic measurements and measuring instruments – Part 311: General terms relating to
measurements – Part 312: General terms relating to electrical measurements – Part 313:
Types of electrical measuring instruments – Part 314: Specific terms according to the type of
instrument
IEC 60359:2001, Electrical and electronic measurement equipment – Expression of
performance
CISPR 16-1 (all parts), Specification for radio disturbance and immunity measuring apparatus
and methods – Radio disturbance and immunity measuring apparatus
CISPR 16-2 (all parts), Specification for radio disturbance and immunity measuring apparatus
and methods – Methods of measurement of disturbances and immunity
CISPR 16-3:2003, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 3: CISPR technical reports
CISPR 16-4-2:2003, Specification for radio disturbance and immunity measuring apparatus
and methods – Part 4-2: Uncertainties, statistics and limit modelling – Measurement
instrumentation uncertainties
CISPR 16-4-1/TR © IEC:2003(E) – 11 –

CISPR 16-4-3:2003, Specification for radio disturbance and immunity measuring apparatus

and methods – Part 4-3: Uncertainties, statistics and limit modelling – Statistical

considerations in the determination of EMC compliance of mass-produced products

CISPR 16-4-4:2003, Specification for radio disturbance and immunity measuring apparatus

and methods – Part 4-4: Uncertainties, statistics and limit modelling – Statistics of complaints

and a model for the calculation of limits

ISO/IEC 17025:1999, General requirements for the competence of testing and calibration

laboratories
ISO Guide:1995, Guide to the expression of uncertainty in measurement (GUM)
ISO:1993, International vocabulary of basic and general terms in metrology, 1993 (the VIM)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE 1 Wherever possible, existing terminology, from the normative standards of Clause 2 is used. Additional
terms and definitions not included in those standards are listed below.
NOTE 2 Terms shown in bold are defined in this clause.
3.1
electromagnetic (EM) disturbance
any electromagnetic phenomenon which may degrade the performance of a device,
equipment or system, or adversely affect living or inert matter
[IEV 161-01-05]
3.2
emission level
the level of a given EM disturbance emitted from a particular device, equipment or system,
measured in a specified way
[IEV 161-03-11]
3.3
emission limit
the specified maximum emission level of a source of EM disturbance

NOTE In IEC this limit has been defined as ‘the maximum permissible emission level’
[IEV 161-03-12]
3.4
influence quantity
quantity that is not the measurand but that affects the result of the measurement
NOTE 1 In a standardised compliance test an influence quantity may be specified or non-specified. Specified
influence quantities preferably include tolerance data.
NOTE 2 An example of a specified influence quantity is the measurement impedance of an artificial mains
network. An example of a non-specified influence quantity is the internal impedance of an EM disturbance source.
[ISO GUM, B.2.10]
– 12 – CISPR 16-4-1/TR © IEC:2003(E)

3.5
interference probability
the probability that a product complying with the EMC requirements will function satisfactorily

(from an EMC point of view) in its normal use electromagnetic environment

3.6
intrinsic uncertainty of the measurand

minimum uncertainty that can be assigned in the description of a measured quantity. In

theory, the intrinsic uncertainty of the measurand would be obtained if the measurand was

measured using a measurement system having a negligible measurement instrumentation
uncertainty
NOTE 1 No quantity can be measured with continually lower uncertainty, inasmuch as any given quantity is
defined or identified at a given level of detail. If one tries to measure a given quantity at an uncertainty lower than
its own intrinsic uncertainty one is compelled to redefine it with higher detail, so that one is actually measuring
another quantity. See also GUM D.1.1.
NOTE 2 The result of a measurement carried out with the intrinsic uncertainty of the measurand may be called the
best measurement of the quantity in question.
[IEC 60359, definition 3.1.11]
3.7
intrinsic uncertainty of the measurement instrumentation
uncertainty of a measurement instrumentation when used under reference conditions. In
theory, the intrinsic uncertainty of the measurement instrumentation would be obtained if the
intrinsic uncertainty of the measurand would be negligible
NOTE Application of a reference EUT is a means to create reference conditions in order to obtain the intrinsic
uncertainty of the measurement instrumentation (4.5.5)
[IEC 60359, definition 3.2.10, modified]
3.8
level
value of a quantity, such as a power or a field quantity, measured and/or evaluated in a
specified manner during a specified time interval
NOTE The level may be expressed in logarithmic units, for example in decibels with respect to a reference value.
[IEV 161-03-01]
3.9
measurand
particular quantity subject to measurement
EXAMPLE –Electric field, measured at a distance of 3 m, of a given sample.

NOTE The specification of a measurand may require statements about influence quantities (see GUM, B.2.9)
[ISO VIM 2.6]
3.10
measurement instrumentation uncertainty
MIU
parameter, associated with the result of a measurement which characterises the dispersion of
the values that could reasonably be attributed to the measurand, induced by all relevant
influence quantities that are related to the measurement instrumentation
[ISO VIM 3.9 and IEC 60359, definition 3.1.4, modified]
3.11
measuring chain
series of elements of a measuring instrument or system that constitutes the path of the
measuring signal from input to the output

CISPR 16-4-1/TR © IEC:2003(E) – 13 –

[ISO VIM 4.4, IEV 311-03-07]
3.12
measurement compatibility
property satisfied by all the results of measurement of the same measurand, characterized by

an adequate overlap of their intervals

[IEV 311-01-14]
3.13
reference conditions
set of specified values and/or ranges of values of influence quantities under which the
uncertainties, or limits of error, admissible for the measurement system are smallest
[IEV 311-06-02]
3.14
reproducibility of results of EMC measurements
closeness of the agreement between the results of successive measurements of the same
measurand carried out under changed conditions as determined by one or more specified
influence quantities.
NOTE In general, this reproducibility is also determined by non-specified influence quantities, hence the
closeness of the agreement can only be stated in terms of probability.
[ISO VIM 3.7, ISO GUM B.2.16]
3.15
sensitivity coefficient
coefficient used to relate the change of a physical quantity due to a variation of one of the
specified or non-specified influence quantities.
NOTE 1 In mathematical form, the sensitivity coefficient is, in general, the partial derivative of the physical
quantity with respect to the varying influence quantity.
NOTE 2 This term and definition is based on the definitions of sensitivity coefficient given in the GUM and the
1)
description given in [5] .
3.16
standards compliance uncertainty – SCU
parameter, associated with the result of a compliance measurement as described in a
standard, that characterises the dispersion of the values that could reasonably be attributed
to the measurand
[based on the ISO GUM B.2.18 and ISO VIM 3.9]

3.17
tolerance
maximum variation of a value permitted by specifications, regulations, etc. for a given
specified influence quantity
[this definition deviates from that given in ISO VIM 5.21]
3.18
true value (of a quantity)
value consistent with the definition of a particular quantity
[ISO GUM B.2.3, ISO VIM 1.19]
———————
1) Figures in brackets refer to the bibliography.

– 14 – CISPR 16-4-1/TR © IEC:2003(E)

3.19
uncertainty source
a source (descriptive, not quantitative) that contributes to the uncertainty of the value of a

measurand, and that shall be divided into one or more relevant influence quantities

NOTE An uncertainty source can be defined also as a qualitative description of a source of uncertainty. In

practice the uncertainty of a result may arise from many possible categories of sources, including examples such

as test personnel, sampling, environmental conditions, measurement instrumentation, measurement standard,
approximations and assumptions incorporated in the measurement method and procedure. Relevant uncertainty
sources are ‘translated’ into one or more influence quantities.

[see 4.2.2 and K3 of [9]]
3.20
variability of results of EMC measurements
closeness of the agreement between the results of successive measurements of the same
measurand carried out under changed conditions as determined by one or more non-
specified influence quantities
NOTE 1 This term and definition is based on ISO VIM 3.7.
NOTE 2 The closeness of the agreement can only be stated in terms of probability.
4 Basic considerations on uncertainties in emission measurements
4.1 Introduction
In a standardised emission compliance measurement, the emission level of an electrical or
electronic product is measured, after which compliance with the associated limit is
determined. The measured level only approximates the true level to be measured, due to
uncertainties induced by the ‘influence quantities’ (3.4). In classical metrology, all relevant
influence quantities are known and the uncertainty arises mainly from the classical
‘measurement instrumentation uncertainty’ because the ‘intrinsic uncertainty of the
measurand’ (3.6) is generally very small. In EMC compliance testing however, major relevant
influence quantities related to the EUT happen to be non-specified [1] and no quantitative
information is available about their values. Hence, for EMC measurements, the intrinsic
uncertainty related to the quantity to be measured may be significant compared to the
uncertainty due to the measurement instrumentation. Therefore, the term ‘standards
compliance uncertainty’ (SCU) has been introduced to distinguish all uncertainties
encountered during an actual EMC compliance test from the measurement instrumentation
uncertainty (MIU), which is a subpart of the SCU. For classical metrology problems it is
generally sufficient to consider only the MIU. Definition of standards compliance uncertainty
(SCU) and other related EMC and uncertainty specific terms are given in Clause 3. Figure 1
illustrates the relation between overall uncertainty of the measurand and the measurement
instrumentation uncertainty and the intrinsic uncertainty of the measurand for the different
situations explained above. It should be noted that the summation operator in Figure 1 (Σ ) is
a symbolic operator. The method to ‘sum’ these uncertainties depends on the probability

distributions and on the correlation of the two uncertainty sources involved.
NOTE It is possible that in the future, classical metrology and EMC disciplines will merge to such an extent that
different terminology and approaches will no longer be needed. For example, the results of the CISPR studies on
measurement instrumentation uncertainty [3] and standards compliance uncertainty shall merge directly, wherever
possible.
The various categories of uncertainties that can be encountered during EMC testing and the
distinction between ‘standards compliance uncertainty’, ‘intrinsic uncertainty of the
measurand’ and ‘measurement instrumentation uncertainty’ is addressed in more detail in 4.2.
Subclause 4.3 discusses briefly the relation between uncertainties of a compliance test and
the risk of interference in practice. Subclause 4.4 describes the steps to be taken to perform
an uncertainty analysis for a standardised emission measurement. Subclause 4.5 gives
methods to verify the validity of the uncertainty budget. Subclause 4.6 gives information on
how to report uncertainty estimates and on how to express the result of a measurement and
its uncertainty. Subclause 4.7 provides some general guidance on the application of the
uncertainties in the compliance criterion. More specific guidance on the application of
uncertainties in pass/fail criteria is under consideration.

CISPR 16-4-1/TR © IEC:2003(E) – 15 –

overall
uncertainty
of the measurand
SCU
measurement
instrumentation
uncertainty
Figure 1a – Typical emission measurement
overall uncertainty =
measurement
instrumentation
uncertainty
MIU
measurement
instrumentation
uncertainty
Figure 1b – An emission measurement with a negligible intrinsic uncertainty of the
measurand
negligible
measurement
instrumentation
uncertainty
Figure 1c – An emission measurement with negligible measurement instrumentation
uncertainty
Figure 1 – Illustration of the relation between the overall uncertainty of a measurand
due to contributions from the measurement instrumentation uncertainty and the
intrinsic uncertainty of the measurand

4.2 Types of uncertainties in emission measurements
In this clause, the different purposes of uncertainty considerations in emission measurements
are discussed first. Depending on the purpose, a different type of uncertainty analysis is
required, and the compliance criterion may be incorporated in different ways depending on
this purpose. Further, the uncertainty sources associated with an emission measurement and
also the corresponding influence quantities are introduced. Finally, different categories of
uncertainties in emission measurements are defined and discussed in more detail as well.

– 16 – CISPR 16-4-1/TR © IEC:2003(E)

4.2.1 Purpose of uncertainty considerations

The measurement result of an EMC emission measurement is subject to uncertainties, and

there may be different reasons to consider the uncertainties in a quantitative way. The

following cases can be considered:

a) qualification of the technical measurement capabilities of a test laboratory;

b) judgement of compliance of a measurement result with respect to the limit;

c) comparison of the measurement results obtained from different test laboratories;

d) comparison of different emission measurement methods;

e) sampled testing of the emission performance of mass-produced products.
The type of uncertainties to be considered differ in each of these cases, as discussed in the
following.
In case a), it may be sufficient to consider the uncertainties of the measuring chain (3.11) and
the uncertainties due to the implementation of the measurement procedures. For instance,
one can consider the technical performance of the measurement equipment, such as the test
site, the measurement receiver and receive antenna. The measurement procedures as carried
out by the personnel and/or by the software can also be evaluated. Application of a calculable
EUT or a reference EUT is a means to evaluate the uncertainty due to the measurement
instrumentation (see Figure 1b).
In case b), the result of an emission compliance test is judged against a given limit. The
resulting uncertainty will include the uncertainties due to the measuring chain and the
measurement procedure, but also the intrinsic uncertainties due to the set up of the EUT or
the operation of the EUT. Compared to a classical metrology measurement, the intrinsic
uncertainty of an EMC emission measurement may have relatively large values. It is a matter
of EMI risk assessment how this overall uncertainty is incorporated in the pass/fail criterion.
One property of the intrinsic uncertainty is that this uncertainty contribution depends not only
on the specification of the measurand, and the class of products, but also on the specification
of the EUT set-up, including the layout and termination of the cables. In first order
approximation, the intrinsic uncertainty is independent of the measurement instrumentation
uncertainty. It is the responsibility of the authors of standards to reduce the intrinsic
uncertainty to an acceptable low level. The magnitude of the intrinsic uncertainty is beyond
the control of the test laboratory and also beyond control of the manufacturer of the product.
Consequently, a manufacturer of a product should not be punished by requiring that the value
of the intrinsic uncertainty shall be taken into account in the pass/fail criterion, i.e. subtracted
from the limit.
NOTE 1 The first edition of CISPR 16-4-2 specifies only MIU for the determination of compliance. However, it was
noted during the development of CISPR 16-4-2 that other uncertainty categories besides MIU affect compliance
determination to some extent. That was the reason to use the more specific title Measurement Instrumentation

Uncertainty in CISPR 16-4-2. Because CISPR 16-4-2 includes CISPR 16-3, per reference, this discrepancy must
be resolved (although CISPR 16-4-2 is a normative document, CISPR16-3 is an informative document). Therefore,
for reasons of consistency, a future amendment of CISPR 16-4-2 may be considered.
An example of case c), is market control by an authority of a certain product. In this case both
test laboratories (manufacturer and authority) judge compliance of the measurement result
against the applicable limit. Also, the two results can be compared with each other directly.
Different samples of the same product may be used by the auditing authority and by the
manufacturer of the product. In this case, the emission performance of the same type of
product may be subject to spread due to tolerances in production and performance of
components. This means that the product itself is a source of uncertainty. Again in this case
an intrinsic uncertainty is present, i.e. differences in set up of the EUT and layout and
termination of the EUT cables may cause significant differences in the outcome of
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