EN 50413 ENG SRP

EUROPEAN STANDARD

_{EN 50413}

NORME EUROPEENNE

EUROPAlSCHE NORM

December 2008

ICS 17.220.20; 33.100.01

English version

Basic standard on measurement and calculation

procedures for human exposure to electric, magnetic and

electromagnetic fields

(0 Hz - 300 GHz)

Norme de base

pour les procedures de mesures

et de calculs pour I'exposition

des personnes aux champs

electriques,

magnetiques et

electromagnetiques

(0 Hz - 300 GHz)

Grundnorm zu Mess- und

Berechnungsverfahren der

Exposition von Personen in

elektrischen, magnetischen und

elektromagnetischen Feldern (0

Hz bis 300 GHz)

This European Standard was approved by CENELEC on 2008-09-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Ovaj Evrposki standard je odobren od CENELEC 2008-09-01. Članovi CENELECa su obavezni da se pridržavaju internih propisa CEN/CENELEC koji pe za davanje ovih Evropskih standarda statusa nacionalnih standarda bez ikakvih izmena.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.

European Committee for Electrotechnical Standardization Comite

Europeen de Normalisation Electrotechnique Europaisches Komitee fur

Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B -1050 Brussels

EN 50413:2008

© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members

Ref. No. EN 50413:2008 E

Foreword

This European Standard was prepared by the Technical Committee CENELEC TC 106X, Electromagnetic fields in the human environment. The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50413 on 2008-09-01.

The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical

national standard or by endorsement (dop) 2009-09-01

latest date by which the national standards conflicting

with the EN have to be withdrawn (dow) 2011 -09-01

Contents

1

Scope 5

2

Normative references 5

3

Definitions 5

4

Introduction..., 9

41General remarks

9

42Static fields

10

43Low frequency range

10

44High frequency range

10

45Multiple frequency fields and multiple sources

11

46Exposure scenario

11

5 Assessment of human exposure by measurement 11

51General remarks 11

52EM field measuremen 12

53Body current measuremen 16

54Specific Absorption Rate (SAR)

17

55Uncertaint 19

56Calibratio 19

6 Assessment of human exposure by calculation • 20

61General aspects

20

62SAR calculation

20

63Uncertainty of calculations

20

7

Phantoms for measurement and computation 21

8

Assessment report 21

81General

21

- 2

-EN 50413:2008

82Items to be recorded in the assessment report

21

9 References 22

Annex A (informative) Analytical models for validation of calculation methods 24 Annex B (informative) Numerical methods 35

Annex C (informative) Uncertainty assessment for the measurement of EMF ... 38

Annex D (informative) Consideration of different types of radio transmission (modulation) ... 43 Bibliography ... 48 Figures

Figure A. 1 - Scheme of the spheroid

... 28

Figure A.2 - k_: versus parameter UR

... Error! Bookmark not defined.

Figure A.3 - Current density induced by an electric field of strength equal to 1 kV/m, 50 Hz versus

parameter UR ... 31 Figure A.4 - Scheme of the spheroid simulating a human being standing on a zero potential plane

... 31

Figure A.5 - Scheme of the spheroid

... 32

Figure A.6 - k_B

versus coordinate y (at z = 0) for different values of the ratio UR

... 33

Figure A.7- k_B versus coordinate z (at y = 0) for different values of the ratio UR

... 34

Tables

Table 1 - Evaluation parameters

... 11

Table D.1 - Characters used to define the class of emission, based on information given in the Radio

Regulations of the International Telecommunication Union (ITU)

... 44

Table D.2 - Relationship between carrier, mean and peak power for the most usual modulation types

in the case of maximum modulated signal

... 46

1

Scope

OBIM

This European Standard gives elements to establish methods for measurement and calculation of quantities associated with the assessment of human exposure to electric,

- 3

-EN 50413:2008

magnetic and electromagnetic fields (EMF) in the frequency range from 0 Hz to 300 GHz. The major intention of this Basic Standard is to give the common background and information to relevant EMF standards. This Basic Standard cannot go into details extensively due to the broad frequency range and the huge amount of possible applications. Therefore it is not possible to specify detailed calculation or measurement procedures in this Basic Standard. This standard provides general procedures only for those product and workplace categories for which there do not exist any relevant assessment procedures in any existing European EMF basic standard.

Овај европски стандард даје елементе за успостављање метода за мерење и обрачун veličina u вези са проценом људске изложености , ( ) електричним магнетним и електромагнетним пољима ЕМФ у 0 300 . фреквенцијском опсегу од Хз до ГХз Главни Намера овог Основног стандарда је да пружи заједничко osnovu и информације релевантним . стандардима ЕМФ Овај стандард не може ићи у детаље potpuno због широког опсега фреквенција и великог broja могућих апликација Због . тога није могуће навести детаљан прорачун или мерне процедуре у овом Основном стандардu. Овај стандард даје опште поступке само за оне производе и на категорије prostora за које не постоје никакве одговарајуће процедуре оцењивања у било коm постојећеm европскom ЕМФ основнom стандардu.

If there exists an applicable European EMF standard focused on specific product or workplace categories then the assessment shall follow that standard. If an applicable European EMF standard does not exist, but an applicable assessment procedure in another European EMF standard does exist, then that assessment procedure shall be used. odgovaraju Ако постоји ći Европски стандард ЕМФ za одређени производ или околину тада ће процена пратити тај стандард примењује се та ( ). , стандард Ако не постоји примењив европски ЕМС стандард али постоји , применљив поступак у другом европском стандарду ЕМФ онда се тај . поступак користи

This standard deals with quantities that can be measured or calculated in free space, notably electric and magnetic field strength or power density, and includes the measurement and calculation of quantities inside the body that forms the basis for protection guidelines.

In particular the standard provides information on • definitions and terminology,

• characteristics of electric, magnetic and electromagnetic fields,

» measurement of exposure quantities,

•instrumentation requirements,

•methods of calibration,

•measurement techniques and procedures for evaluating exposure,

•calculation methods for exposure assessment.

Овај стандард се бави величинама које могу мерити или

,

израчунати у слободном простору као електричним и магнетним

,

пољима густина снаге и укључује мерење и обрачун интензитета

ових величина унутар тела које се

израчунавају на основу

смерница.

:

Посебно стандард пружа информације о следећем

•

дефиницијама и терминологији,

•

карактеристике електричних магнетних и електромагнетна

,

,

поља

•

Мерењу величина која указују на изложености

•

мерни захтевима,

•

методама калибрације

,

•

мерним техникама и процедурама за процену изложености

,

•

методама за обрачун за процену изложености

.

- 4

-EN 50413:2008

2

Normative references

Void.

3 Definitions

ДЕФИНИЦИЈЕ

For the purpose of this document, the following terms and definitions apply.

3.1 action values

magnitude of directly measurable parameters, provided in terms of electric field strength (E), magnetic field strength (H), magnetic flux density (Б) and power density (S), at which one or more of the specified measures in Directive 2004/40/EC must be undertaken. Compliance with these values will ensure compliance with the relevant exposure limit values (from 2004/40/EC)

, . За потребе овог документа примењују се следећи термини и дефиниције 3.1 акционе вредности ( ) Интензитет јаина директно мерљивих величина, као јачина електричног ( ), ( ), ( ) поља јачине Е јачина магнетног поља Х густину магнетног флукса Б ( ), 2004 / 40/ . и густина снаге С на које се примењују мера из Директиве ЕЦ Коришћење овако дефинисаних вредностима ће обезбедити усклађеност ( 2004/40/ ) са одговарајућим вредностима изложености из ЕЦ 3.2 antanna АНТЕНА

device that serves as a transducer between a guided wave for example in a coaxial cable and a free space wave, or vice versa

Уређај који служи као прелазни медијум између система вођења таласа на пример у коаксијалном каблу и слободног простора простирања , таласа или обрнуто 3.3 basic restriction ОСНОВНА ОГРАНИЧЕЊА

restrictions on exposure to time-varying electric, magnetic, and electromagnetic fields that are based directly on established health effects (from ICNIRP guidelines)

ограничења о излагању временски променљивим електричним , , магнетним електромагнетним и поља која су заснована непосредно на ( ) утврђеним здравственим ефектима из ИЦНИРП смерница 3.4 contact current КОНТАКТНА СТРУЈА

current flowing into the body resulting from contact with a conductive object in an electromagnetic field. This is the localised current flow into the body (usually the hand, for a light brushing contact)

Струја која протиче у телу услед контакта са проводним објекта у . електромагнетног поља Ово је локализован тренутни проток у ( , телу обично рука за лагани контакт) 3.5 current density (J)Густина Струје

current per unit cross-sectional area flowing inside the human body as a result of direct exposure to electromagnetic fields, expressed in the unit ampere per square m (A/m ) Струја по јединици попречног пресека унутар лјудског тела условљена

(A/m ). дејством електромагнетног пољаѕ на тело изражена јединицом

3.6

electric flux density (D) ЕЛЕКТРИЧНА ИНДУКЦИЈА

vector quantity obtained at a given point by adding the electric polarization P to the product of the electric field strength Е and the permittivity of free space

ε

0_:

0

D

r

=

ε

E P

r

+

r

Electric flux density is expressed in units of coulombs per square m (C/m2_).

NOTE In vacuum, the electric flux density is at all points equal to the product of the electric field strength and the permittivity of free space: D = to

E

r e w Векторска величина (тренутна вредност добијена вектрорским збиром ) вектора електричне поларизације Pr на производ вектроа електричног поља и пропустљивост слободног простора

ε

0_: 0

D

r

=

ε

E P

r

+

r

3.7

electric field strength (E )

% ^ vector quantity obtained at a given point that represents the force (F) on an infinitely small charge (q) divided

o_W by the charge: E = F

-q

Electric field strength is expressed in the unit volt per m (V/m) - 5

-EN 50413:2008 3.8 exposure

exposure occurs when there is an electric, magnetic or electromagnetic field at the same location as the person from an external source

( ) , Изложеност експозиција се јавља када постоји електрично магнетнo или електромагнетно поље из спољног извора на истој локацији као и . особа 3.9

exposure limit values ГРАНИЧНЕ ВРЕДНОСТИ ИЗЛОЖЕНОСТИ

limits on exposure to electromagnetic fields which are based directly on established health effects and biological considerations. Compliance with these limits will ensure that workers exposed to electromagnetic fields are protected against all known adverse health effects (from 2004/40/EC)

Ограничења о излагању електромагнетним пољима која су заснована . директно на утврђеним здравственим ефектима и биолошким разлозима Поштовање ових граница ће осигурати да су радници изложени електромагнетним пољима заштићени од свих познатих штетних ефеката ( 2004/40/ ) по здравље од ЕЦ 3.10 far-field region ДАЛЕКА ЗОНА ИЗЛОЖЕНОСТИ

region of the field of an antenna where the radial field distribution is essentially dependent inversely on the distance from the antenna. In this region the field has a predominantly plane-wave character, i.e. locally uniform distribution of electric field and magnetic field in planes transverse to the direction of propagation

NOTE In the far-field region the vectors of the electric field Е and the magnetic field H are perpendicular to each other and the quotient between the value of the electric field strength E and the magnetic field strength H is constant and equals the impedance of free space Zo.

Област од антене где постоји радијална компонента поље а . интензитет је у реципрочно сразмерн удаљености од антене У , овом региону поље има претежно карактер раванског таласа односно постоји електричног поље и магнетног поље сунормални један на други и нормалани на правац простирања. НАПОМЕНА У крајње поља региону вектори електричног поља фунти и магнетног поља Х су нормала једни на друге и количник између вредности електричног поља Е снаге и јачине магнетног поља Х је константна и износи представља импедансу слободног простора

Z

0_. 3.11

impedance of free space

the impedance of free space Z₀ is defined as the square root of the free space permeability u.₀ divided by the permittivity of free space e₀

3.12 Isotropic ИЗОТРОПНОСТ

qualifies a physical medium or technical device where the relevant properties are independent of the direction

- 6

P

EN 50413:2008 ( ) , Карактеристика физичког медијума средине или техничких уређаја где су релевантне . особине независне правца 3.13 induced current (/) ИНДУКОВАНА СТРУЈА

current induced inside the body as a result of direct exposure to electromagnetic fields, expressed in the unit ampere (A)

3.14

linearity of measurement instrument ЛИНЕАРНОСТ МЕРНОГ ИНСТРУМЕНТА

maximum deviation over the measurement range of the measured quantity from the closest linear reference curve defined over a given interval

Максимално одступање из мерног опсега измерене количине у односу на линеарну

референтну криву дефинисана у одређеном интервалу.

3.15

magnetic flux density (B) МАГНЕТНА ИНДУКЦИЈА

the field vector in a point that results in a force (F) on a charge (q) moving with the velocity (v) F = q ( v x B ) The magnitude of the magnetic flux density is expressed in the unit tesla (T)

је векторска величина која као резултат има постојање силе на тачкасто

наелектрисанје које се креће брзином рпоље

Магнетногиндукција се изразава јединицомТесла Т ( ) 3,16

3.16

magnetic field strength (H)

vector quantity obtained at a given point by subtracting the magnetization M from the magnetic flux density B divided by the permeability of free space u₀:

вектор јачине магнетног поља ( )Х

вектор количина добијене у датом тренутку одузимањемвекторамагнетизације М од

магнетн е индукције подељен маг. пропустљивости слободног простора:

Magnetic field strength is expressed in the unit ampere per metre (A/m)

NOTE In vacuum, the magnetic field strength is at all points equal to the magnetic flux density divided by the permeability of free space: H = B I u₀

3.17 modulation МОДУЛАЦИЈА

is the process of modifying the amplitude, phase and/or frequency of a periodic waveform in order to convey information , , је процес модификације амплитуде фазе или фреквенције периодичног таласног . сигнала како би се пренела информација 3.18 near-field region БЛИСКА ЗОНА ЗРАЧЕНЈА

Region generally in proximity to an antenna or other radiating structure, in which the electric and magnetic fields do not have a substantially plane-wave character, but vary considerably from point to point. The near-field region is further subdivided into the reactive near-field region, which is closest to the radiating structure and that contains most or nearly all of the stored energy, and the radiating near-field region where the radiation field predominates over the reactive field, but lacks substantial plane-wave character and is complex in structure

, Област у близини антене или друге зрачече структуре у којој су електрично и магнетна поља немају особине раванског таласа и интензитет им се значајно мења од тачке до тачке. , Блиска зона зрачења се даље дели на реактивну блиску зону која је најближа зрачечој структури и садржи највећи део енергије електромагнетног таласа извора и зрачећу ( ) блиску зону зрачења где радијационо полје пропагациони талас доминира у односу на , . реактивно поље али зачетак раванског таласа је комплексне структуре 3.19 peak value ВРШНА МАКСИМАЛНА ВРЕДНОСТ ( )

the peak value of the electric or magnetic field strength or magnetic flux density represents the maximum magnitude of the field vector. It is built up out of three individual components of the electric or magnetic field strength or magnetic flux density, which are instantaneous values in three mutually orthogonal directions

EN 50413:2008

вршна вредност електричног или магнетног поља јачине или магнетне индукције

.

представља максималну величину поља вектора Сачињена је од три компоненте по три

.

ортогонална правца

3.20 permeability

property of a material which defines the relationship between magnetic flux density B and magnetic field strength H. It is commonly used as the combination of the permeability of free space (u₀) and the relative permeability for specific materials (/v_r) B

M = Wo = — where

u,

is the relative permeability of the material u₀ is the permeability of free space. The permeability is expressed in units of henry per metre (H/m)

- 7

P

EN 50413:2008 3.21 permittivity (£)

property of a dielectric material, e.g., biological tissue, defined by the electric flux density D divided by the electric field strength E

where

i, is the relative permittivity of the material Eo is the permittivity of free space. The permittivity is expressed in units of farads per metre (F/m)

3.22

phantom ФАНТОМ

simplified mode! of the human body or body part composed of materials with dielectric properties close to the organic tissue Упрошћени модел људског тела или дела тела сачињен од материјала који је сличних . диелектричних карактрериситка као и биолошко ткиво power density (S)

power per unit area normal to the direction of electromagnetic wave propagation. The power density is expressed in units of watts per square m (W/m2₎

NOTE 1 For plane waves the power density (S), electric field strength (£) and magnetic field strength (H) are related by the impedance of free space Zo

NOTE 2 Although many survey instruments indicate power density units, the actual quantities measured are E or H, or the square of those quantities

3.24 probe СОНДА

input device of a measuring instrument, generally made as a separate unit, which transforms the measured input value to a suitable output value

, Улазни уређај мерног инструмента уопђтено направлјен да раздвојни уређај који . трансформише мерену улазну величину у одговарајућу излазну вредност 3.25 reference level РЕФЕРЕНТНИ НИВОИ

these levels are provided for practical exposure assessment purposes to determine whether the basic restrictions are likely to be exceeded. Some reference levels are derived from relevant basic restrictions using measurement and/or computational techniques, and some address perception and adverse indirect effects of exposure to EMF (from ICNIRP guidelines) Ови нивои су предвиђени у сврху практичне процене изложености када се утврди да основна . ограничења вероватно могу бити премашена Неки референтни нивои су изведени из / одговарајућих основних ограничења помоћу мерења и или рачунарских метода, или неких уочених ефеката и нежељених индиректних ефекта изложености ЕМФ по ИЦНИРП смерницама ( ) NOTE In any particular exposure, situation, measured or calculated values can be compared with the appropriate reference level. Compliance with the reference level will ensure compliance with the relevant basic restriction. If the measured or calculated value exceeds the reference level, it does not necessarily follow that the basic restriction will be exceeded. However, whenever a reference level is exceeded it is necessary to test compliance with the relevant basic restriction and to determine whether additional protective measures are necessary

, , НАПОМЕНА У било којој ситуацији при изложености измерене или израчунате вредности могу се . поредити са одговарајућим референтним нивоима Усклађеност са референтним нивоима ће . обезбедити усклађеност са одговарајућим основним ограничења Ако измерена или израчуната , вредност премашује референтну ниво то не мора нужно да значи да основна ограничење ће бити . , премашена Међутим кад год референтни ниво је премашен неопходно је тестирати усклађеност са основним ограничења и да се утврди да ли додатне заштитне мере су неопходне 3.26 root-mean-square (r.m.s.) Efektivna vrednost – koren srednjeg kvadrata

the r.m.s. value is obtained by taking the square root of the average of the square of the value of the time-varying function taken throughout a suitable period of time

NOTE For periodic functions a suitable time interval is any multiple of the period of the function For non-periodic functions the time interval used must be recorded

. . . kvadratnih vredosti р м с вредност се добија тако што квадратни корен просека током одговарајућег периода НАПОМЕНА За периодичне функције погодан временски интервал је више периода koji se функције За апериодичне функција временски интервал користи мора бити . забележен

3.27 root-sum-square (rss) Koren sume kvadrata

the value rss is the square root of the sum of three field quantities squared, measured in mutually orthogonal directions

NOTE Any phase information is disregarded 3.28 Вредност РСС је квадратни корен збира три vrednпоља количине квадрата мерено , међусобно ортогонална правца 3.28 НАПОМЕНА Свака фаза информације занемарује - 8

P

EN 50413:2008

specific absorption rate (SAR)

time derivative of the incremental electromagnetic energy (dW ) absorbed by (dissipated in) an incremental mass (dm) contained in a volume element (dV ) of given mass density (p)

where

r.m.s. value of the electric field strength in the tissue in V/m; conductivity of body tissue in Sim; density of body tissue in kg/m3_:

heat capacity of body tissue in J/kg K;

time derivative of temperature in body tissue in K/s. 3.29

unperturbed field NEPERTURBOVANO POLJE (neuznemireno)

field that exists in a space in the absence of a person or an object that could influence the field NOTE The field measured or calculated with a person or object present may differ considerably

Поље које постоји у простору у одсуству лица или предмет који би могао утицати на

поље

НАПОМЕНА Поље koje se iz

мери или израчунаa

са неком особом или објектom

може se

значајно разликовати

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-EN 50413:2008

4 Introduction

4.1

General remarks

Electric, magnetic and electromagnetic fields can have direct and indirect effects on the human body. Depending on the frequency of the fields these effects can be stimulation of central nervous system in the low frequency range and thermal effects in the high frequency range. Besides these direct effects there exist several indirect effects such as the occurrence of contact currents or the possible influence on the intended operation of active medical implants. Also the type (continuous wave, pulsed, single/multi-frequency, low/high frequency range), the distribution (single/multiple sources) and the localisation (whole body, head and trunk, limbs) of the electric, magnetic and electromagnetic fields greatly influence the basic concepts or principles that can be used and the field quantities which have to be assessed.

Електричнa, магнетна и електромагнетна поља могу имати директне и индиректне ефекте на . , људско тело У зависности од фреквенције поља ови ефекти могу бити od стимулацијe централног нервног система у ниском фреквентном опсегу do термалних ефеката у високом фреквентном . опсегу Поред ових директних ефеката постоји неколико индиректни ефекти као што су појаве контактних струја или могућег утицаја на предвиђену funkciju активних медицинских импланта. , ( , , mono

Такође тип континуирани талас пулсирајући hromatski talas/ polihromatski tаlas, нискo / високo

),

фреквенцијски опсег raspodela polja (iz jednog ili више извора и локализација цело тело главу и ) ( ,

, ) ,

труп екстремитети од електричних магнетних и електромагнетна поља у великој мери утиче на

основне концепте или принципе који се могу користити и pri sagledavanju veličina које се процеnjuju.

Special attention should be paid to the rationale and to the special requirements of the protection guidelines which are used for exposure assessment.

-phis standard is intended to be used for the assessment of emissions from products and comparison of these with the exposure levels for the general public given in Council Recommendation 1999/519/EC [9], _and with exposure assessments in the workplace to determine compliance with the requirements of Council pirective 2004/40/EC [10]. The Council Recommendation 1999/519/EC [9] provides basic restrictions and derived reference levels for _e)<posure of the general public in the areas where they spend significant time.

-phe Council Directive 2004/40/EC [10] provides exposure limit values and action values for exposures in the w0rkplace. This document may be used for demonstration of compliance with National implementation of the pirective. The basic restrictions given in the Recommendation, and the exposure limit values given in the Directive, _are in both cases the actual limits which are expressed in terms of quantities that are mostly not measurable: including induced currents for low frequency, specific absorption rate (SAR) for higher frequency and power density for the highest frequencies. The values are the same as the basic restrictions for general public and occupational exposures respectively given in the ICNIRP guidelines (1998) [7], [8].

Посебна пажња треба да се обрати на образложење и посебним захтевима заштите смерница које . се користе за процену изложености -ЈЗУ стандард је намењен да се користи за процену емисија из производа и поређењем ових са 1999/519/ [9], нивоима изложености за јавност дате у Препоруци Савета ЕЦ и са оценама изложености на радном месту за утврђивање усаглашености са захтевима Савета пирецтиве 2004/40/ЕЦ [10]. 1999/519/ [9] ) Препорука Савета ЕЦ даје основне ограничења и изведених референтних нивоа за е <посуре опште јавности у областима у којима проводе доста времена . -Директива Савета 2004/40/ЕЦ феномен [10] пружа таласима граничне вредности и акционе 0 . вредности изложености за у в ркплаце Овај документ може да се користи за демонстрацију . складу са Националном спровођење пирецтиве , , Основни ограничења дата у препоруци а граничне вредности излагања дате у Директиви су у оба : случаја стварне границе које су изражене у смислу количине које углавном нису мерљиви , ( ) укључујући индукованих струја за ниске фреквенције специфична стопа апсорпције САР за . веће фреквенције и снаге густине за највиших фреквенција Вредности су исти као основних , ограничења за опште јавне и професионалне изложености односно наведених у ИЦНИРП (1998) [7], [8]. смерницама

The reference levels given in the Recommendation, and the action values given in the Directive, are in both cases derived from the actual limits and are expressed in terms of quantities that are measurable: including electric field strength, magnetic field strength and contact current. The values are the same as the reference levels for general public and occupational exposures respectively given in the ICNIRP guidelines (1998) [7], [8]. The ICNIRP Guidelines [7], [8] provide basic restrictions and derived reference levels for both occupational and general public exposure. E=xp°sure _{assessments may be based either on the reference levels (action values), or on the basic restriction} (exposure limit value) taking account of specific characteristics of the particular field source or device being assessed. In general, either calculation or measurement procedures can be used for the assessment of field quantities. In specific circumstances there may be advantages of using one or the other of these. If both are suitable, then one may be used to validate the results of the other. Which ever is used, it must be applied for realistic exposure scenarios. For any assessment procedure a maximum allowable uncertainty should be chosen. The level of this maximum allowable uncertainty will depend on which assessment procedure is used. For any procedure it shall be as low as is reasonable. The actual uncertainty for each procedure shall be below the maximum.

The following paragraphs give some special guidance for several of the topics mentioned above. 4.2 Static fields

Static electric and magnetic fields are independent from each other and shall - if necessary - both be assessed. 4.3 Low frequency range

In the low frequency range (up to 100 kHz) the electric and magnetic fields are mainly independent from each other and shall - if necessary - both be assessed. For a given exposure scenario the electric field strength depends only on the voltage used; the magnetic field strength or magnetic flux density depends only on the electric currents.

4.4 High frequency range

There exist several field types which should be assessed differently depending on the distance r from and the dimension D of the radiating source. Table 1 indicates whether to measure E or H or both at different distances from the field source

For unintentional radiators, if it is not known whether the conditions for far field or radiating near field apply, then it is -

EN 50413:2008

necessary to measure both £ and H.

4.5 Multiple frequency fields and multiple sources

In performing exposure evaluation all relevant frequency components and field sources have to be taken into account. Proper summation procedures given in ICNIRP Guidelines [7], ICNIRP Statement [8], EU Council Recommendation [9] and EU Workers Directive [10] have to be used. In order to get a more precise exposure evaluation in addition it may be necessary to take into account not only the amplitudes of electric and magnetic fields but also the phases of individual field components.

In the low frequency range (stimulation effects) current densities, electric and magnetic field strengths shall be superposed in a linear manner (weighted). In the high frequency range (thermal effects) power densities shall be superposed also in a linear manner, whereas electric and magnetic field strengths have to be superposed in a squared mariner (weighted).

4.6 Exposure scenario

Depending on the field geometry, exposure evaluation has to be performed accordingly. That may require whole body or partial body exposure evaluation.

In the low-frequency range basic restrictions and exposure limit values are given for central nervous system (CNS) tissue only. For the assessment of inhomogeneous or highly- localized exposure situations (i.e. small sources used close to the body) this has to be taken into account.

5 Assessment of human exposure by measurement

Subclause 5.1 gives an overview of which measurements are necessary to assess human exposure to electric, magnetic and electromagnetic fields.

5.1 General remarks

Measurements of human exposure to electric, magnetic and electromagnetic fields can be classified as follows:

•measurement of electric, magnetic or electromagnetic field quantities (i.e. S, E, H, S);

•measurement of the limb induced current;

•measurement of the contact current;

•measurement of the Specific Absorption Rate (SAR);

•measurement of the temperature.

To make meaningful measurements, the behaviour and characteristics (for example frequency, time-variability of emission, input power) of the source of exposure (field or current) shall be determined and the operation of the measurement equipment understood. Irrespective of the type of signal, time domain measurement may be used. This can be especially helpful for non-sinusoidal, very fast, and pulsed signals. Also, the exposure quantities measured should include all those needed to assess the extent of human exposure arising from the operation of the source. What shall be measured is the maximum level to which someone is exposed under the operating conditions of the source that are used when a person is permitted access.

The expected emission characteristics of the source should be understood, and it should be confirmed that these match the results of measurements. Sometimes the source will be well documented, in which case the predicted emissions may be comparatively simple to establish. Sometimes the source will be undocumented and its characteristics must be determined mostly by measurement. There will also be influences on the behaviour of the source, such as ground conductivity, presence of reflecting objects etc. and these shall be considered.

Measurement equipment should be calibrated and suitable for the measurements to be made. The uncertainties associated with its use for the measurement undertaken shall be established.

Sometimes the exposure position is well defined, but often it may be necessary to determine the location at which maximum exposure will occur. This may be achieved by either a preliminary survey of the areas around a source or by the setting up a spatial 2D/3D-measurement matrix. Measurements should be made at all positions on the matrix. When the position of maximum exposure has been identified then detailed measurements should be made. The distances between different measurement points will depend e.g. on the kind of chosen measurement method and on frequency.

The assessment of internal electromagnetic field quantities in general can be difficult or impossible since internal quantities in real organisms cannot be measured directly. Consequently, studies to assess them are carried out using physical or numerical models of the human body referred to as phantoms. The physical and electric characteristics (dielectric properties) of experimental phantoms are manufactured to represent as closely as possible the response of a person to an incident electromagnetic field.

5.2 EM field measurement

5.2.1 General remarks

The field to be measured shall be the unperturbed field (without presence of a person).

EM field measurements have to differentiate between low- and high-frequency field measurements.

The range for low frequency measurements is from 0 Hz up to 100 kHz and the range for high frequency measurements is from 100 kHz up to 300 GHz.

NOTE The underlying physiological effects of electromagnetic fields on the human body have no sharp frequency limit value to distinguish between stimulation and thermal effects; this also shows up in the selection of the measurement equipment necessary.

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EN 50413:2008

For meaningful EM field measurements to be carried out the following information needs to be known:

-the type of field source, e.g. supply current and voltage, radiated power;

-the characteristics of the source of fieid e.g. frequency, operational behaviour, modulation, duty cycle;

-the measuring instruments and their characteristics e.g. measurement principle;

-the evaluation bases such as standards, limit values etc.;

-the uncertainty of the measurements.

Once these are known the most appropriate method of field measurement can be chosen. 5.2.2

Measurement equipment

EM field measurement equipment consists of two parts, the probe or field sensing element, and the measuring instrument, which processes the signal from the probe and indicates the value of the EM field quantity with an analogue or digital display.

The measuring equipment should be suitable for the desired application. The characteristics of the relevant sources, the environmental conditions of the locations where persons can be present and the characteristics of the measuring system should be taken into account.

The following aspects of measuring equipment should be considered:

•the equipment should have sufficient dynamic and frequency range for the particular application. The measurement

equipment should be designed for practical use in rough industrial environment and for outdoor use, e.g. broadcasting towers, where this is appropriate;

•generally, field measurement equipment can be differentiated into broadband and narrowband (frequency selective)

instrumentation;

• frequency selective measurement equipment can provide information on field strength and also information about the spectral characteristics of the measured fields. Typically spectrum analysers, tuned receivers or pass-band filters are used for this purpose. Narrow band instrumentation could be used if frequency resolution and higher sensitivity is needed or where the signal to be measured is discontinuous (e.g. pulse-modulated with a low pulse repetition frequency);

• broadband measurement equipment normally indicates field strengths independent of signal frequency. 5.2.3 Measuring instrumentation

In most cases, measuring instruments should respond to, and indicate, r.m.s. values, but for some purposes, instruments responding to peak values should be used. This may apply, for example, if the peak value is well-defined but the r.m.s. value varies considerably with time and with the averaging time of an r.m.s. measurement.

Several factors may influence the measurement results and should be observed carefully. A non-exhaustive list of such factors is given below:

• Power supply

The instrument shall not be influenced by fields from its own power supply. It shall also be unaffected by any interaction of external fields with its power supply or mains connection. It is often preferable for the equipment to be operated from batteries.

• Measurement range

The measurement range of the instrumentation is required to be in accordance with the field strengths to be measured.

The sensitivity should be sufficient to determine the lowest level to be measured within the accuracy at that level as stated by the instrument's manufacturer.

• Frequency range

The frequency range of the measuring equipment should be sufficient to cover the frequencies of the EM field sources to be characterised.

• Sampling rate

The sampling rate of the measuring instrument shall be higher than twice the highest signal frequency. • Integration time

The integration time for an r.m.s. measurement shall exceed the period of the lowest frequency, or modulation frequency, present in the signal. In some cases, a much longer time is required in order to obtain a stable and repeatable measured value.

• Readability of display

In order for the operator to be far enough away from the meter to avoid perturbation of the EM field, the display shall be easy to read from a distance. Alternatively, the use of remote displays is recommended.

» Uncertainty

The uncertainty of the measuring equipment shall be known and has to be considered in the final assessment. • Environmental conditions

The measuring equipment shall be appropriate to the environmental conditions (e.g. temperature, humidity, vibration, EMC-phenomena) existing at the time of measurement.

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EN 50413:2008

• Response to ionising radiation, iight and out-of-band electromagnetic fields

The response of the measuring equipment to ionising radiation, artificial light, sunlight or corona discharge should be considered. The response of the instrument to out-of-band fields should be specified for both magnetic and electric fields.

• Overload and failure levels

Overload and failure levels of the instruments including the probes shall be specified for continuous wave (CW) and pulsed signals within the frequency range of the probe.

- 13

EN 50413:2008

5.2.4 EM field probes

Electric and magnetic field probes shall be designed in such a way that the probe does not significantly affect the field to be measured.

The electric field strength probe used for measurements in accordance with this standard shall respond primarily to the electric field component of an electromagnetic field at the frequencies of emission of the device under test.

The magnetic field probe used for measurements in accordance with this standard shall respond primarily to the magnetic field component of an electromagnetic field at the frequencies of emission of the device under test.

In addition, the following shall be taken into account: • Single-axis and multiple (isotropic) probes

Usually probes are designed either to indicate a single spatial field component or the resultant of all spatial field components. A probe with a single-axis sensor responds only to one field component and, consequently it should be oriented to read the maximum value, or alternatively it should be aligned in three mutually orthogonal directions to measure separately the three spatial components of the field.

Multiple sensor arrangements can be used in suitable configurations to combine the spatial field components and to enable isotropic measurements independent of polarisation and direction of incidence. Three orthogonally arranged elements are required for an isotropic probe that can be used in any orientation with respect to the field. These probes usually measure the resultant field strength as the root sum-square (rss);

• Broadband and narrowband probes

Selective instrumentation can provide information on field strength and also information about the spectral characteristics of the measured fields.

Broadband instrumentation normally indicates field strength independent of signal frequency. For the assessment of human exposure to electromagnetic fields (EMF), frequency-dependent limits have to be taken into account, and this can be achieved by using a filter with a corresponding frequency characteristic (shaped frequency response) or by carrying out a Fast Fourier Transform (FFT) and then comparing the calculated values with the frequency-dependent limits. It is also possible to make a simple broadband field strength measurement and to measure separately the spectral content of the field e.g. with a spectrum analyser. The spectrum analyser data can be used to weight the broadband measurement. This is particularly useful when making repetitive field strength measurements around an emitter with a constant spectrum;

• Size of the probe

The size of the probe shall be appropriate to the spatial variation of the field that is measured and to the specific requirements of the applied measurement and assessment methods.

5.2.5 Aspects during measurement 5.2.5.1 Measuring set up

Before the measurement, it has to be ensured that the exposure limits for the personnel doing the measurement will not be exceeded.

If the presence of the operator affects the measurement results, the measuring system or the probe shall be set up on a non-conductive stand or supported using a non-conductive pole.

The measurements should include a location of the probe in the centre of the exposed body volume, e.g. trunk or head.

5.2.5.2 Measuring equipment

The bandwidth of the instrument shall be appropriate to the frequency of the EM field being measured.

Broadband measuring equipment does not give spectral information on the measured field. Therefore the result, which is usually the total field strength of all spectral components within the measurement bandwidth, has to be compared with the lowest exposure limit. If the frequencies of the source (or sources) are known, it is appropriate to use the lowest exposure limit of those frequencies.

Perturbation from the environment (e.g. temperature, humidity, mechanical vibration, levels of EMC-Phenomena) should be avoided.

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EN 50413:2008

5.2.5.3 Precautions during measuring

A high-frequency incident electromagnetic field, where the wavelength is smaller than the size of the object, can induce surface currents on metallic objects, which can result in a scattering wave. The re-radiated field superimposes on the primary radiated field and reduces overall measurement accuracy. Probes operating very close to metallic surfaces can directly couple (capacitively or inductively) into the probe elements, despite their small size. There may also be influence on the probe performance from mains-frequency currents in metallic conductors, and for Radio Frequency (RF) measurement the mains power sensitivity shall be known. A minimum distance of the probe to metallic objects is necessary. Although this distance is usually comparable to several probe diameters, it is difficult to generalise the requirement. The documentation of the probe therefore shall include the minimum distance to the source or any metallic objects, which may depend on frequency as well as probe dimensions.

The electric field can couple into magnetic field probes and vice versa. The suppression ratio shall be specified by the manufacturer and shall be taken into account when measuring an electric field in the presence of a strong magnetic field (or vice versa). The suppression of the unwanted field shall be sufficient to allow reliable measurements to be made.

5.2.5.4 EM field

5.2.5.4.1 Static and low frequency fields

Electric and magnetic fields shall be considered separately.

The presence of a human body can influence the electric field being measured. To prevent this, the person making the measurement and anyone else shall be sufficiently far from the meter and the measuring system or the probe shall be set up on a non-conductive stand or supported using a non-conductive pole.

5.2.5.4.2 High frequency fields

The presence of a human body can influence the electric or magnetic field being measured. Proximity effects of the observer as well as others that may be in the vicinity of the probe should be avoided. Where it is necessary to prevent this, the person making the measurement and anyone else shall be sufficiently far from the meter and the measuring system or the probe shall be set up on a non-conductive stand or supported using a non-conductive pole. In the frequency range between 10 GHz and 300 GHz the estimation of the body exposure shouid be done on the basis of the power density.

5.2.5.4.3 Near-field

In the near field the electric and magnetic field components are not related to each other and depend on the EM field source. Therefore both electric and magnetic field components shall be considered.

To make meaningful near-field measurements, the following conditions should be taken into account:

•the dimensions of the probe should be much less than a wavelength at the highest frequency of the area of the

incident EM field;

•the probe should not produce significant scattering of the incident EM field.

Evaluation of power density in the near field region without knowledge of the phase relations between E and H should be done by measuring of the electric and magnetic field components and calculation by equation S = E H . This is a worst case estimation which assumes that the E and H fields are perpendicular and in phase with each other. If phase and direction information about the fields are available then a more exact assessment of S shall be made. 5.2.5.4.4 Far-field

In the far-field it is possible to determine

• the electric field strength by measuring the magnetic field strength and conversion with the equation

E = H Z

₀

;

• the magnetic field strength by measuring the electric field strength and conversion with the equation

H = ±;

Zo

• power density S.

NOTE The power density can also be determined by measurement of one field component (E- or H-field) and

E

2

calculation by equation S = — or S

= H~ ■ Z

₀.

5.2.6 Execution of EM field measurements

5.2.6.1 Identifications before the measurements

Before the measurements of EM field, the following identifications shall be made:

•determine the relevant EM field sources and tneir characteristics (e.g. frequency, power, modulation, radiation

characteristics, operating and worst case conditions);

•determine possible relevant influences on the field, such as ground conductivity, presence of reflecting objects, etc.;

•determine the location of the exposed persons and accessible areas;

•determine the time of exposure (high frequency only);

•make a rough assessment of the exposure to prevent overexposure of the person performing the measurement;

-

EN 50413:2008

•choose type of measurement (broadband or narrowband);

•select the adequate measurement system in compliance with the characteristics of the relevant EM field source;

•check the proper operation of the probe and measurement equipment.

The measuring instrument shall be selected taking into account:

•the type of field (£-, H- field);

•the frequency range of the EM field source;

•the measuring time (CW- or Pulsed field);

•the polarization of the EM field source.

5.2.6.2 Preliminary scan

A preliminary scan may be performed to determine the distribution of the field. The overall result of the scan shall be documented.

5.2.6.3 Detailed measurement

•Selection of the measuring procedure.

•The locations for a detailed scan should be chosen taking into account the preliminary scan result.

•Positioning the probes in accordance to the activities and the locations of the exposed persons (head, trunk, sit,

stand).

•Define the conditions of the relevant EM field sources during the measuring.

•Perform a plausibility check on the measurements.

5.3 Body current measurement

Body currents are defined in terms of

• induced current density in the CNS (below 10 MHz),

•limb induced currents (between 10 MHz and 110 MHz),

•contact current when touching/grasping an object (either the human body or the object or both may be located in an

electromagnetic field) (below 110 MHz).

If there is any possibility that the exposure limits will be exceeded for limb induced currents or contact currents then a human body should not be included in the measurement circuit.

5.3.1 Measurement of induced current densities

The induced current density in the CNS cannot be measured directly. Therefore induced body current densities are normally calculated.

5.3.2 Measurement devices for limb induced currents

The principal technique for assessing limb currents is the clamp-on current-transformer.

Current sensing in such units may be accomplished using either narrowband techniques, e.g. spectrum analysers or tuned receivers (which offer the advantage of being able to determine the frequency distribution of the induced current in multi-source environments, or broadband techniques using diode detection or thermal conversion.

NOTE 1 A phantom can be used to simulate the body's equivalent impedance.

NOTE 2 Parallel plate current meters can also be used to measure leg currents in some very specific situations but they are not recommended generally.

5.3.3 Measurement devices for contact current

The current measurement device can be inserted between the hand of the person and the conductive object. The measurement technique may consist of a metallic probe (definite contact area) to be held by hand at one end of the probe while the other end is touched to the conductive object. A clamp-on current sensor (current transformer) can be used to measure the contact current which is flowing into the hand in contact with the conductive object.

NOTE A phantom can be used to simulate the body's equivalent impedance. 5.3.4 Assessment of body current measurements

Leg current shall be assessed using one of the devices described in 5.3.2. Arm current shall be measured with a current transformer. Calibration of the device shall meet the requirements of 5.6 and uncertainties shall be addressed as specified in 5.5. The requirements of 5.1 shall also be met. Leg current shall be measured at the normal exposure position. If no such position is specified measurements shall be made at appropriate accessible positions. The leg current at each measurement position shall be recorded.

Arm current shall be measured at the normal exposure position. If no such position is specified then measurements shall be made at appropriate accessible positions. The arm current at each measurement position shall be recorded. Contact current shall be assessed using one of the devices described in 5.3.3. Calibration of the device shall meet the requirements of 5.6 and uncertainties shall be addressed as specified in 5.5. The requirements of 5.1. shall also be met. Contact current shall be measured at the normal exposure position. If no such position is specified then measurements shall be made at appropriate accessible positions. The contact current at each measurement position shall be recorded.

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EN 50413:2008

5.4 Specific Absorption Rate (SAR)

There are three main methods to directly measure SAR in human body phantoms:

•internal electric field strength measurements for assessment of localised SAR;

•internal temperature measurement for assessment of localised SAR;

•calorimetric measurement of heat transfer for assessment of whole-body-averaged SAR.

5.4.1 Internal electric field strength measurements

Assessment of SAR via E-field measurement is performed using a miniature probe that is positioned in a liquid-filled phantom model of the human body or a part of it (for example: the head), which is exposed to an electromagnetic fieid. From the measured E-field values, the SAR distribution and the maximum mass averaged SAR value can be calculated according to:

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EN 50413:2008

<

03 i—\

The £-field probe should have an isotropic response (within ± 1 dB). Because of the short wavelength in tissue and since the field may have large spatial gradients, the probe size should be as small as possible (for example: dipole length 2 mm to 4 mm). The probe should affect the field as little as possible. Care has to be taken to avoid significant influence on SAR measurements by any reflection from the environment (such as floor, positioner, etc.) or from unknown sources.

NOTE To obtain 3-dimensional SAR distributions in exposed human phantoms by the E-field-probe technique, it is preferable to use an automatic probe positioning system, for example an industrial robot.

The measurement equipment shall be calibrated according to 5.6 as a complete system. Sensitivity, linearity and isotropy of the probe system shall be determined in the tissue equivalent liquid. Uncertainties should be addressed as specified in 5.5. Measurements in close vicinity to media interfaces result in errors due to boundary effects. These effects depend on the probe size and can be quantified as a function of distance from the surface using a waveguide calibration set-up. After quantification these effects can be compensated in order to minimize errors.

5.4.2 Internal temperature measurements

Assessment of SAR via temperature measurement is performed using a temperature probe that is positioned in a liquid-filled phantom model of the human body or a part of it (for example: the head), which is exposed to an electromagnetic field. From the measured temperature increase, the local SAR distribution can be calculated using the formula:

SAR = c, — At

with the temperature rise AT" during the small time interval A / . The temperature-rise measurement has to start at a thermal balance. This equation is applicable under the condition that the heat diffusion effect can be disregarded. If the diffusion effect cannot be disregarded, an integral equation including the heat-diffusion factor has to be employed. Common types of available equipment for temperature measurements in exposed body models use probes consisting of a high-resistance thermistor or optical probes. Temperature probes have very small tips allowing high spatial resolution. The temperature resolution of these probes is typically 0,005 K to 0,1 K, which limits the sensitivity of SAR to about 0,03 W/kg. In order that the probe does not perturb the electromagnetic field, it is constructed using high-resistance thermistors connected to high-high-resistance leads or by using fibre optics.

NOTE To determine the three-dimensional SAR distribution or local peak SAR in a phantom model, the temperature probe has to be moved inside the phantom using a similar positioning system as for E-field probes.

Temperature rise in a phantom model (or even at the surface of a real human being) can also be assessed by infrared imaging devices. Hence, a thermographic camera may be used to determine the 2-dimensional temperature-rise and SAR distribution in solid phantom cross-sections or at surfaces. First the phantom has to reach uniform temperature. Directly after the exposure of a few seconds the phantom is placed in front of the thermographic camera and a thermographic image is immediately taken to map the temperature-rise profile. Temperature profiles inside the phantom may be taken by separating the phantom at specially prepared cuts.

The sensitivity of temperature sensors is relatively low in comparison to E-field probes. In order to achieve a reasonable sensitivity in SAR assessment via temperature measurement, in general, high-power exposure sources have to be applied to get a sufficient temperature increase in a short time interval. Low-power devices (e. g. hand-held mobile phone) have to be fed in the test with an additional (external) source.

Calibration of temperature-measurement equipment includes, beside the general probe calibration, a careful evaluation of heat diffusion processes.

5.4.3 Calorimetric measurements of heat transfer

Calorimeters allow the measurement of the whole-body averaged or partial-body averaged SAR for human body models, exposed to electromagnetic fields. Averaged SAR is derived according to the equation below by measuring the total energy absorbed in a body with the mass during the exposure time: