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Not for reproduction CISPR/A (Cape Town – Netherlands)
Original: English October 2005
INTERNATIONAL ELECTROTECHNICAL COMMISSION
INTERNATIONAL SPECIAL COMMITTEE
ON RADIO INTERFERENCE (CISPR)
Sub-Committee A: Radio Interference Measurements and Statistical Methods
Ref CISPR A projects: Agenda item 11
Subject: On basic terms used without proper definitions
Recently several discussions took place between members of the CISPR A community on definitions. Table 1 gives a list of examples of basic terms that need more specific definition for use within the EMC standardization community. Before CISPR starts to define complex terms such as „alternative test method‟ it is necessary to have a common understanding and an agreed definition of basic terms such as „test‟ and „measurement‟.
This paper provides some considerations on basic terms and definitions that are used within the EMC community. Recommendations are given for adoption of a generic process to support some basic terms and definitions. Adoption of the recommendations may be starting point for agreement on definitions of more complex terms.
2 Present implicit situation within EMC standards
Presently, within EMC standards the terms „test‟, „testing‟ and „measurement‟ are often interchanged. However, „testing‟ refers more often to immunity (usually a go/no-go test) and
„measurement‟ is likely to refer to emission (normally the emission level is measured and recorded as a function of frequency). IEC 61000-1-1 does not address the basic terms „test‟
and „measurement‟ explicitly.
Some people believe it is correct to make a clear distinction between 'test' and measurement'. The difference is sometimes explained as follows. A 'test' always has a go-no go outcome, while a 'measurement' only returns one or more figures. With the latter interpretation the „test‟ could be considered as a generic process that comprises two basic steps (see Figure 1). The first process step may be a measurement of an emission level or the measurement of the audio quality of a DVD player while the player was subject to a certain electromagnetic stress level. The second step is considered always a judgement of the determined properties of that test article. This may be a judgement whether the emission level is below a certain limit or whether the audio quality satisfies certain performance conditions or not. Consequently an immunity test may include either a „measurement‟ of quantitative performance properties of the test article, or it may include the „determination‟ of the qualitative properties. Table 2 gives
some more examples of EMC-related tests and how this fits in the scheme of Figure 1. It is concluded is that the present implicit (or non-defined) situation within EMC standards and the EMC standardisation community is that a „measurement‟ is considered as process step as
part of a „test‟. Furthermore, a „test‟ is always considered to include a pass/fail judgement, while a „measurement‟ does not include a pass/fail judgement.
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Table 1 List of examples of basic terms that need definition for use within EMC
test testing measurement
test procedure testing procedure measurement procedure test method testing method measurement method test technique testing technique measurement technique test protocol testing process measurement process test uncertainty testing laboratory measurement laboratory alternative test method measurement uncertainty established test method etc etc experiment
etc etc etc etc
Figure 1 Generic process of a test: present implicit interpretation within EMC
performance of the specified properties Determination of Judgement of the Test article in question specified determined properties of the properties of the
test article test article
Table 2 Examples of the present use of ‘test’ and ‘measurement’ in the EMC community
using the basic process of Figure 1 Brief description of the aim of Includes process step 1 Includes process step 2 the standard
Emission test Measurement of the emission level Judgement of measurement result against a specified emission limit Conducted immunity test of a Determination of the proper Judgement of the measurement product functioning of the product results against pass/fail criteria Evaluation test of a FAR Measurement of the NSA Judgement of the NSA results against a compliance criterion Antenna calibration Measurement of the antenna factor Not applicable
Antenna performance test Measurement of the cross-polar Judgement cross-polar performance performance against pass/fail criterion
Measurement of the balance Judgement balance performance against pass/fail criterion
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3 Present definitions of ‘test’ and ‘measurement’ within IEC standards
Table 3 provides definitions of „test‟, „testing‟ and „measurement‟ that can be found in existing IEC/ISO standards. If we look carefully at the existing definitions of „test‟ and „testing‟ in Table 3, then we see that „test‟ or „testing‟ does not include a pass/fail judgement.
Consequently the general process depicted in Figure 1 would not comply with the present ISO/IEC definitions. It would be very difficult to change these existing ISO/IEC definitions of „test‟ with to aim to have a better match with the present usage of „test‟ in the EMC community. Therefore it is proposed to adopt the IEC/ISO definitions of „test‟ and „measurement‟ as outlined in Table 3 and to solve the problem within the EMC community. The next section gives a proposal for that.
Table 3 Definitions of ‘test’, ‘testing’ and ‘measurement’ that can be found in existing
Term Definition Reference
Test Technical operation that consists of the determination of one or more ISO/IEC Guide 2: 1991 characteristics of a given product, process or service according to a specified procedure.
Measurement Process of experimentally obtaining information about the magnitude of VIM draft 3rd ed. (IEC a quantity 1/1940/DC)
1. Measurement implies a measurement procedure, based on a theoretical model.
2. In practice, measurement presupposes a calibrated measuring system, possibly subsequently verified.
Testing Determination of one or more characteristics of an object of conformity ISO/IEC 17000:2004 assessment, according to a procedure (3.2)
NOTE “Testing” typically applies to materials, products or processes.
Testing Action of carrying out one or more tests. ISO/IEC Guide 2: 1991
Test Determination of one or more characteristics according to a procedure. ISO 9000: 2000
4 Proposal for a generic process and some basic definitions to be used in the EMC community
The same two–step process as used in Figure 1, is used to define a new generic process that may be the basis in the future for definitions of „test‟ and „measurement‟ etc. Starting point is that the whole process can be designated as „conformity assessment‟. The term „conformity assessment‟ is defined in ISO/IEC 17000 (Table 4). Furthermore, the term „test‟ as defined by ISO/IEC 17000 is adopted, which does not include the process of pass/fail judgement. Next, the ISO/IEC 17000 term „inspection‟ is used to designate the second process step of „pass/fail judgement (Table 4). Using the generic process as outlined in Figure 2 and adopting the existing definitions in the Tables 3 and 4 also means that „measurement‟ must be considered
as a specific case of „testing‟. So „measurement‟ is (if applicable) one possible way of „testing‟.
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Table 4 Definition of ‘conformity assessment’ and ‘inspection’ (ISO/IEC 17000: 2004)
Conformity Demonstration that specified requirements relating to a product, process, system, person or assessment body are fulfilled
NOTE 1 The subject field of conformity assessment includes activities defined elsewhere in this International Standard, such as testing (4.2), inspection (4.3) and certification (5.5), as well as the accreditation (5.6) of conformity assessment bodies (2.5).
NOTE 2 The expression “object of conformity assessment” or “object” is used in this International Standard to encompass any particular material, product, installation, process, system, person or body to which conformity assessment is applied. A service is covered by the definition of a product (see Note 1 to 3.3).
Inspection Examination of a product design, product (3.3), process or installation and determination of its conformity with specific requirements or, on the basis of professional judgement, with general requirements
NOTE Inspection of a process may include inspection of persons, facilities, technology and methodology.
Figure 2 Proposal for generic process of conformity assessment using ISO/IEC 17000
Object of Determination of Determination of Conformity conformity one or more its conformity with conclusion assessment characteristics specific according to a requirements
5 Conclusions & recommendation
The present implicit (or non-defined) situation within EMC standards and the EMC standardisation community is that a „measurement‟ is considered as process step as part of a „test‟ and that a „test‟ is considered to include a pass/fail judgement.
This interpretation is not in compliance with the present ISO/IEC definitions of „test‟.
It is proposed to use the term „conformity assessment‟ as the generic process that we specify in different EMC standards. Furthermore it is proposed to adopt the basic terms „testing‟ and „inspection‟ as the two main steps of this generic process (see Figure 2).
Agreement on the generic process as outlined in Figure 2 and the associated existing ISO/IEC definitions of terms will open the way to agreement on more complex definitions such as „alternative test method‟.