EN 50413:2008

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Grundnorm zu Mess- und Berechnungsverfahren der Exposition von Personen in elektrischen, magnetischen und elektromagnetischen Feldern (0 Hz bis 300 GHz)Norme de base pour les procédures de mesures et de calculs pour l'exposition des personnes aux champs électriques, magnétiques et électromagnétiques (0 Hz - 300 GHz)Basic standard on measurement and calculation procedures for human exposure to electric, magnetic and electromagnetic fields (0 Hz - 300 GHz)33.100.01Elektromagnetna združljivost na splošnoElectromagnetic compatibility in general17.220.20Measurement of electrical and magnetic quantitiesICS:Ta slovenski standard je istoveten z:EN 50413:2008SIST EN 50413:2009en,fr,de01-marec-2009SIST EN 50413:2009SLOVENSKI
STANDARD
EUROPEAN STANDARD EN 50413 NORME EUROPÉENNE
EUROPÄISCHE NORM December 2008
CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2008 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50413:2008 E
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 procédures de mesures
et de calculs pour l'exposition
des personnes aux champs électriques, magnétiques et électromagnétiques
(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.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on applica-tion 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 lan-guage 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.
(dop)
2009-09-01 – latest date by which the national standards conflicting with the EN have to be withdrawn
(dow)
2011-09-01
__________
– 3 – EN 50413:2008 Contents 1 Scope . 5 2 Normative references. 5 3 Definitions . 5 4 Introduction . 9 4.1 General remarks . 9 4.2 Static fields . 10 4.3 Low frequency range . 10 4.4 High frequency range. 10 4.5 Multiple frequency fields and multiple sources . 11 4.6 Exposure scenario . 11 5 Assessment of human exposure by measurement . 11 5.1 General remarks . 11 5.2 EM field measurement . 12 5.3 Body current measurement . 16 5.4 Specific Absorption Rate (SAR) . 17 5.5 Uncertainty . 19 5.6 Calibration . 19 6 Assessment of human exposure by calculation . 20 6.1 General aspects . 20 6.2 SAR calculation . 20 6.3 Uncertainty of calculations . 20 7 Phantoms for measurement and computation . 21 8 Assessment report . 21 8.1 General . 21 8.2 Items 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 – kE versus parameter L/R . 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 L/R . 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 – kB versus coordinate y (at z = 0) for different values of the ratio L/R . 33 Figure A.7– kB versus coordinate z (at y = 0) for different values of the ratio L/R . 34 SIST EN 50413:2009

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
– 5 – EN 50413:2008 1 Scope This European Standard gives elements to establish methods for measurement and calculation of quantities associated with the assessment of human exposure to electric, 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. 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. 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. 2 Normative references Void. 3 Definitions 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 (B) 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) 3.2 antenna device that serves as a transducer between a guided wave for example in a coaxial cable and a free space wave, or vice versa 3.3 basic restriction restrictions on exposure to time-varying electric, magnetic, and electromagnetic fields that are based directly on established health effects (from ICNIRP guidelines) 3.4 contact current 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) SIST EN 50413:2009

– 7 – EN 50413:2008 3.13 induced current (I) 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 maximum deviation over the measurement range of the measured quantity from the closest linear reference curve defined over a given interval 3.15 magnetic flux density (B) the field vector in a point that results in a force (F) on a charge (q) moving with the velocity (v) F
= q (v × B) The magnitude of the magnetic flux density is expressed in the unit tesla (T) 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 µ0:
MBH−µ=0 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 / µ0 3.17 modulation is the process of modifying the amplitude, phase and/or frequency of a periodic waveform in order to convey information 3.18 near-field region 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 3.19 peak value 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 xyzVVtVtVt=++222Pmax()()() SIST EN 50413:2009

µ0 is the permeability of free space. The permeability is expressed in units of henry per metre (H/m) 3.21 permittivity (ε) property of a dielectric material, e.g., biological tissue, defined by the electric flux density D divided by the electric field strength E DEεε=ε=r0 where 0r is the relative permittivity of the material 00 is the permittivity of free space. The permittivity is expressed in units of farads per metre (F/m) 3.22 phantom simplified model of the human body or body part composed of materials with dielectric properties close to the organic tissue 3.23 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 (E) and magnetic field strength (H) are related by the impedance of free space Z0 2002HEHES⋅==⋅=ZZ 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 input device of a measuring instrument, generally made as a separate unit, which transforms the measured input value to a suitable output value 3.25 reference level 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) 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 SIST EN 50413:2009

– 9 – EN 50413:2008 3.26 root-mean-square (r.m.s.) 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 3.27 root-sum-square (rss) 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 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 (ρ) ==VWtmWtddddddddSARρ SAR is expressed in units of watts per kilogram (W/kg) NOTE SAR can be calculated by: ρσ2iSARE=,
0iatddttTcSAR= where Ei r.m.s. value of the electric field strength in the tissue in V/m; 1 conductivity of body tissue in S/m; ρ density of body tissue in kg/m3; ci heat capacity of body tissue in J/kg K; dT / dt time derivative of temperature in body tissue in K/s. 3.29 unperturbed field 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 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. Special attention should be paid to the rationale and to the special requirements of the protection guidelines which are used for exposure assessment. SIST EN 50413:2009

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]. 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. Exposure 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 necessary to measure both E and H. SIST EN 50413:2009

– 11 – EN 50413:2008 Table 1 – Evaluation parameters
Reactive near fieldRadiating near fieldFar fieldDistance a r r <
< r < 2D² /
2D² /
< r E,H ~ 1/r
No No Yes Z = E/H ≠ Z0 ≈ Z0 = Z0 To measure E and H E or H E or H a Strongly depending on type of
radiating structure (D: biggest dimension of the radiating structure; i.e. diameter of a parabolic antenna). If the EM field is modulated, Annex D gives some guidance on how to determine the required values for the exposure assessment. 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 manner (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. B, 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. SIST EN 50413:2009

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; SIST EN 50413:2009

– 13 – EN 50413:2008 • 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. • Response to ionising radiation, light 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. SIST EN 50413:2009

– 15 – 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 should 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 HES⋅=. 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 0Z⋅=HE; • the magnetic field strength by measuring the electric field strength and conversion with the equation EH=0;Z • power density S. SIST EN 50413:2009
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