EN 50357:2001

SLOVENSKI STANDARD
01-januar-2002
Evaluation of human exposure to electromagnetic fields from devices used in
Electronic Article Surveillance (EAS), Radio Frequency Identification (RFID) and
similar applications
Evaluation of human exposure to electromagnetic fields from devices used in Electronic
Article Surveillance (EAS), Radio Frequency Identification (RFID) and similar
applications
Ermittlung der Exposition von Personen gegenüber elektromagnetischen Feldern von
Geräten, die in der elektronischen Artikelüberwachung (en: EAS), Hochfrequenz-
Identifizierung (en: RFID) und ähnlichen Anwendungen verwendet werden
Evaluation de l'exposition humaine aux champs électromagnétiques (EMFs) émis par les
dispositifs utilisés pour la surveillance électronique des objets (EAS), l'identification par
radiofréquence (RFID) et les applications similaires
Ta slovenski standard je istoveten z: EN 50357:2001
ICS:
13.280 Varstvo pred sevanjem Radiation protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50357
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2001
ICS 13.280; 33.100.01
English version
Evaluation of human exposure to electromagnetic fields
from devices used in Electronic Article Surveillance (EAS),
Radio Frequency Identification (RFID) and similar applications
Evaluation de l'exposition humaine aux Ermittlung der Exposition von Personen
champs électromagnétiques (EMFs) gegenüber elektromagnetischen Feldern
émis par les dispositifs utilisés pour la von Geräten, die in der elektronischen
surveillance électronique des objets Artikelüberwachung (en: EAS),
(EAS), l'identification par radiofréquence Hochfrequenz-Identifizierung (en: RFID)
(RFID) et les applications similaires und ähnlichen Anwendungen verwendet
werden
This European Standard was approved by CENELEC on 2001-07-03. 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
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, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
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
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50357:2001 E
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 106X (former TC 211),
Electromagnetic fields in the human environment.
The text of the draft was submitted to the Unique Acceptance Procedure and was approved by CENELEC as
EN 50357 on 2001-07-03.
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) 2002-07-01
- latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-07-01
Annexes designated "informative" are given for information only.
In this standard, annexes A and B are informative.
__________
– 3 – EN 50357:2001
Contents
Foreword. 1
Introduction . 4
1 Scope . 5
2 Physical quantities, units and constants. 5
2.1 Quantities . 5
2.2 Constants . 6
3 Terms and definitions. 6
3.1 General . 6
3.2 Specific for EAS, RFID and similar applications. 11
4 Measurements and calculations for equipment compliance . 14
4.1 Simple measurements to show compliance with derived reference levels. 14
4.2 Measurements and analysis to show compliance with basic restrictions . 23
4.3 Numerical modelling to show compliance with basic restrictions. 27
4.4 Measurement of limb and contact currents. 29
5 Measurements for field monitoring. 29
5.1 Field measurements . 29
5.2 Additional evaluation. 30
6 Exposure from sources with multiple frequencies or complex waveforms. 30
7 Uncertainty. 30
7.1 Evaluating uncertainties. 31
7.2 Examples of typical uncertainties . 31
7.3 Overall uncertainties . 32
Annex A (informative) Characteristics of equipment . 35
A.1 EAS Equipment . 35
A.2 EAS desktop and activation/deactivation equipment. 39
A.3 RFID equipment. 39
Annex B (informative) Information for numerical modelling. 45
B.1 Introduction. 45
B.2 Anatomical models. 45
B.3 Electrical properties of tissue. 46
B.4 Comparison of induced currents, modelled using different sizes of prolate spheroid . 49

Introduction
This document presents procedures for the evaluation of human exposure to electromagnetic fields (EMF’s)
from Devices used in electronic article surveillance (EAS), radio frequency identification (RFID) and similar
applications. The work has been carried out in response to:
1)
� The ICNIRP Guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic
fields (up to 300 GHz) [1];
� European Council Recommendation 1999/519/EC on the limitation of exposure of the general public to
electromagnetic fields 0-300 GHz (the EC Recommendation) [2];
� European Council Directive 73/23/EEC on the harmonisation of the laws of member states relating to
electrical equipment designed for use within certain voltage limits (the LV Directive) [3];
� European Council Directive 1999/5/EC on radio equipment and telecommunications terminal equipment
and the mutual recognition of their conformity (the R&TTE Directive) [4].
The techniques presented in this document may also be used to demonstrate compliance to other National
or International requirements.
Electromagnetic fields interact with the human body and other biological systems through a number of
physical mechanisms. The main mechanisms of interaction are based on nervous system effects and
heating. These effects are dependent on frequency and are defined by biologically relevant quantities such
as magnetic flux density, induced current density and specific absorption rate. These quantities are not
directly measurable so they must be determined either, by calculation for each case, or by measuring a
reference quantity which has a pre-derived relationship to them.
The examples used in this document are taken from the EC Recommendation and from the ICNIRP
Guidelines. They each contain a series of Basic Restrictions for magnetic flux density, induced current
density, power density and specific absorption rate as well as a series of derived Reference Levels
In any particular exposure situation, measured or calculated values can be compared to the appropriate
reference level. The reference levels are generally obtained from the basic restriction by mathematical
modelling and laboratory experimentation at specific frequencies. They reflect maximum coupling of the fields
to the exposed human being, thereby providing maximum protection. Respect of the reference level will
ensure respect of the relevant basic restriction. If the measured value exceeds the reference level, it does not
necessarily follow that the basic restriction is also exceeded. Under those circumstances, more detailed
evaluation techniques will be necessary which are specific to that type of equipment and exposure.
This document adopts a staged approach to compliance assessment. The first stage is a simple measurement
against the appropriate derived Reference Levels. If the device meets these, there is no requirement for further
assessment. Stage 2 is a more complex series of measurements, coupled with analysis techniques. Again, if
the device meets the appropriate levels, there is no requirement for further assessment. Stage 3 requires
detailed modelling and analysis to show compliance with the Basic Restrictions. Device compliance can be
shown using any one of the stages; it is not necessary to use more than one, unless an assessment using
Stages 1 or 2 fails to demonstrate compliance.
The devices covered by this document normally have non-uniform field patterns. Often these devices have a
very rapid reduction of field strength with distance and operate under near-field conditions where the
relationship between electric and magnetic fields is not constant. This, together with typical exposure
conditions for different device types, is detailed in annex A.
Measurements and methods are derived with reference to:
1. Work carried out within CENELEC
2. Notes and explanatory text from the EC Recommendation and the ICNIRP Guidelines
2)
3. Similar techniques proposed or adopted by IEC , especially in the case of desktop equipment [5].
4. Other, specifically referenced techniques.

1)
International Commission on Non-Ionising Radiation Protection
2)
International Electrotechnical Committee

– 5 – EN 50357:2001
1 Scope
This European Standard applies to devices used in Electronic Article Surveillance (EAS), Radio Frequency
Identification (RFID) and similar applications. The objective of the Standard is to specify, for such equipment,
the methods for demonstration of compliance with basic restrictions or reference levels related to human
exposure to electromagnetic fields.
The Council Directive 1999/5/EC [4], Article 3.1(a), defines essential requirements for equipment that is
either radio equipment or telecommunications equipment or both; with regard to the protection of the health
and safety of the user and any other person. This document may be used for demonstration of compliance
to the Council Directive with reference to human exposure to electromagnetic fields (EMF’s). There are
additional requirements covered by Article 3.1(a), which are not included in this document.
The Council Directive 73/23/EEC [3], Article 2, stipulates that the Member States take all appropriate
measures to ensure that electrical equipment may be placed on the market only if, having been constructed
in accordance with good engineering practice in safety matters in force in the Community, it does not
endanger the safety of persons, domestic animals or property when properly installed and maintained and
used in applications for which it was made. The principal elements of those safety objectives are listed in
annex I clause 2b. This document may be used for demonstration of compliance to the Council Directive
only with reference to human exposure to electromagnetic fields (EMF’s). There are additional requirements
covered by Article 2 and annex I clause 2b, which are not included in this document.
The Council Recommendation 1999/519/EC [2] provides Basic Restrictions and derived Reference Levels
for exposure of the general public in the areas where they spend significant time. This document may be
used for demonstration of equipment compliance to the Council Recommendation on this basis, but there
may be additional specific National or International requirements which are not included.
The ICNIRP Guidelines [1] provide Basic Restrictions and derived Reference Levels for both occupational
and general public exposure. This document may be used for demonstration of equipment compliance to
ICNIRP Guidelines on this basis, but there may be additional specific National or International requirements
which are not included.
Other Standards can apply to products covered by this document. In particular this document is not
designed to assess the electromagnetic compatibility with other equipment, medical or otherwise. It does not
reflect any product safety requirements other than those specifically related to human exposure to
electromagnetic fields.
It is also possible to use this document as a basis to demonstrate compliance to other National and
International Guidelines or Requirements with regard to human exposure from EMF’s. In these cases, other
Restrictions and Levels may be used.
2 Physical quantities, units and constants
2.1 Quantities
The internationally accepted SI units are used throughout this document
Quantity Symbol Unit Dimension
-2
Current density J ampere per square metre Am
-1
Electric field strength E volt per metre Vm
-2
Electric flux density D coulomb per square metre Cm
-1
Electric conductivity siemens per metre Sm
�
Frequency f hertz Hz
-1
Magnetic field strength H ampere per metre Am
Magnetic flux density B tesla  (Vs/m)T
-3
Mass density kilogram per cubic metre kgm
�
-1
Permeability henry per metre Hm
�
-1
Permittivity farad per metre Fm
�
-2
Power density S watt per square metre Wm
-1
Specific absorption rate SAR watt per kilogram Wkg
Wavelength metre m
�
Temperature T kelvin K
2.2 Constants
Physical Constant Symbol Magnitude
8 -1
Velocity of light c 2,997 x 10 ms
-12 -1
Permittivity of free space 8,854 x 10 Fm
�
-7 -1
Permeability of free space
� 4� x 10 Hm
Impedance of free space Z 120� (or 377) �
3 Terms and definitions
3.1 General
3.1.1
average (temporal) absorbed power (P )
avg
the time – averaged rate of energy transfer defined by:
t 2
P � P(t)dt
avg
�
t �t
2 1 t1
where t and t are the start and stop time of the exposure (the period t – t is the exposure duration)
1 2 2 1
3.1.2
averaging time (t )
avg
the appropriate time over which exposure is averaged for purposes of determining compliance
3.1.3
Basic Restrictions
restrictions are the restrictions on exposure to time-varying electric, magnetic, and electromagnetic fields that
are based directly on established health effects
3.1.4
conductivity (�)
the ratio of the conduction – current density in a medium to the electric field strength

– 7 – EN 50357:2001
3.1.5
contact current
current flowing into the body by touching a conductive object in an electromagnetic field
3.1.6
current density (J)
the electromagnetic field induced current per unit area inside the body
3.1.7
dielectric constant (�)
see permittivity
3.1.8
duty factor (or duty cycle)
the ratio of pulse duration to the pulse period of a periodic pulse train. Also, may be a measure of the
temporal transmission characteristic of an intermittently transmitting RF source such as a paging antenna
by dividing average transmission duration by the average period for transmissions. A duty factor of 1,0
corresponds to continuous operation
3.1.9
electric field strength (E)
the magnitude of a field vector at a point that represents the force (F) on an infinitely small charge (q) divided
by the charge
F
E �
q
3.1.10
electric flux density (D)
the magnitude of a field vector that is equal to the electric field strength (E) multiplied by the permittivity (�)
D��E
3.1.11
energy density
the energy impinging per unit area normal to the direction of the electromagnetic wave propagation
3.1.12
exposure
exposure occurs whenever and wherever a person is subjected to electric, magnetic or electromagnetic
fields or to contact current other than those originating from physiological processes in the body and other
natural phenomena
3.1.13
exposure level
The value of the quantity used when a person is exposed to electromagnetic fields or contact currents
3.1.14
exposure, direct effect of
result of a direct interaction in the exposed human body from exposure to electromagnetic fields
3.1.15
exposure, partial body
partial body exposure results when fields are substantially non-uniform over the body. Fields that are non-
uniform over volumes comparable to the human body may occur due to highly directional sources, standing
waves, re-radiating sources or in the near field

3.1.16
exposure, non-uniform
non-uniform exposure levels result when fields are non-uniform over volumes comparable to the whole
human body. This may occur due to standing waves, scattered radiation or in the near field. See “exposure,
partial body”
3.1.17
far-field region
that region of the field of an antenna where the angular field distribution is essentially independent of the
distance from the antenna. In this region (also called the free space region), the field has a predominantly
plane-wave character, i.e. locally uniform distribution of electric field strength and magnetic field strength in
planes transverse to the direction of propagation
3.1.18
induced current
current induced inside the body as a result of direct exposure to electromagnetic fields
3.1.19
intrinsic impedance of free space (Z )
the ratio of the electric field strength to the magnetic field strength of a propagating electromagnetic wave in
free space. This does not apply in the near-field region
3.1.20
magnetic flux density (B)
the magnitude of a field vector that is equal to the magnetic field H multiplied by the permeability (µ) of the
medium
B��H
3.1.21
magnetic field strength (H)
the magnitude of a field vector in a point that results in a force (F) on a charge (q) moving with velocity (v)
F � q�� � �H �
[or magnetic flux density divided by permeability of the medium, see “magnetic flux density”]
3.1.22
multiple frequency fields
the superposition of two or more electromagnetic fields of differing frequency
3.1.23
near-field region
a 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 two sub-regions. The reactive near-field region is closest to the
radiating structure and contains most or nearly all of the stored energy. The radiating near-field region is
where the radiation field predominates over the reactive field, but lacks substantial plane-wave character and
is complicated in structure
3.1.24
permeability (µ)
the 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 and the relative
permeability for specific dielectric materials
µ = µ µ = B/H
R 0
-1
where µ is the permeability of the medium expressed in henry per metre (Hm )

– 9 – EN 50357:2001
3.1.25
permittivity, (�)
the property of a dielectric material (e.g. biological tissue) which defines the relationship between electrical
flux density D and electrical field strength E. It is commonly used as the combination of the permittivity of
free space and the relative permittivity (or dielectric constant) for specific dielectric materials
ε = µ µ = D/H
R 0
-1
where � is the permittivity of the medium expressed in farads per metre (Fm )
3.1.26
polarisation
that property of electromagnetic fields describing the time-varying direction and amplitude of the electric field
vector: specifically, the figure traced as a function of time by the extremity of the E-Field vector at a fixed
location in space, as observed along the direction of propagation. In general, the figure is elliptical and it is
traced in a clockwise or counter clockwise sense. The commonly referenced circular and linear polarisations
are obtained when the ellipse becomes a circle or a straight line, respectively. Clockwise sense rotation of
the electric vector is designated right – hand polarisation and counter clockwise sense rotation is designated
left-hand polarisation
3.1.27
power density (S)
power per unit area normal to the direction of electromagnetic wave propagation. For plane waves the
power density (S), electric field strength (E) and magnetic field strength (H) are related by the impedance of
free space, i.e. 377 ohms
NOTE  Although many survey instruments indicate power density units, the actual quantities measured are E or H, or the square of
those quantities.
E
S � � 377H � EH
-1 -1 -2
In particular where E and H are expressed in units of Vm and Am , respectively, and S in Wm .
It should be noted that the value of 377 � is only valid for free space, far field measurement conditions (and does not apply for inductive
devices operating in the reactive near field).
3.1.28
power density, average (temporal)
the instantaneous power density integrated over a source repetition period. This averaging is not to be
confused with the measurement averaging time
3.1.29
power density, plane-wave equivalent
commonly used term associated with any electromagnetic wave, equal in magnitude to the power density of
a plane wave having the same electric (E) or magnetic (H) field strength
3.1.30
root-mean-square (rms)
the effective value or the value associated with joule heating, of a periodic electromagnetic wave. The rms
value is obtained by taking the square root of the mean of the squared value of a function
NOTE  Although many survey instruments indicate rms, the actual quantity measured is root-sum-square (rss) (equivalent field
strength). The value rss is obtained from three individual rms field strength values, measured in three orthogonal directions combined
disregarding the phases. The measured rss value is the maximum possible (worse case) and can be quite different from the true root-
mean-square (rms) value.
3.1.31
root-sum-square (rss)
the effective value or the value associated with joule heating, of a periodic electromagnetic wave. The rss
value is obtained by taking the square root of the sum of the squared value of a function
n
X � ��X
� n
3.1.32
scattered radiation
an electromagnetic field resulting from currents induced in a secondary, conducting or dielectric object by
electromagnetic waves incident on that object from one or more primary sources. The scattering object is
sometimes called a “re-radiator” or “secondary radiator”
3.1.33
specific absorption rate (SAR)
the 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 (� )
d dW d � dW �
� �
SAR � � � �
� �
� �
dt dm dt �dV
� �
� �
–1
SAR is expressed in units of watts per kilogram (Wkg ).
NOTE  SAR can be calculated by:
� E
i
SAR �
�
dT
SAR �c
i
dt
at t
where
E : rms value of the electric field strength in the tissue in V/m
i
� : conductivity of body tissue in S/m
� : density of body tissue in kg/m
c : heat capacity of body tissue in J/kg K
i
dT
: initial time derivative of temperature in body tissue in K/s
dt
3.1.34
wavelength
the wavelength (�) of an electromagnetic wave is related to the frequency (f) and velocity (c) by the
expression
c
� �
f
– 11 – EN 50357:2001
3.2 Specific for EAS, RFID and similar applications
3.2.1
active tags
tags which use batteries as a partial or complete source of power. They are further differentiated by
separating them into those with replaceable batteries and those with batteries that are sealed for life as an
integral part of the tag
3.2.2
activator
a device which changes inactive transponders so that they are able to transpond
3.2.3
air interface
the conductor-free medium, usually air, between a transponder and the reader through which data
communication is achieved by means of a modulated inductive, capacitive or propagated electromagnetic
field
3.2.4
antenna
antennas are conductive elements that radiate, and/or receive energy in the radio frequency spectrum
3.2.5
bandwidth
the range or band of frequencies in the electromagnetic spectrum within which a system is capable of
receiving and transmitting
3.2.6
capacitive coupling
systems using electric fields as a means of transferring data or power are said to use capacitive coupling.
This is sometimes also referred to as electrostatic coupling
3.2.7
carrier
the frequency used to carry data by appropriate modulation of the carrier waveform
3.2.8
CEPT
Conférence Européenne des Postes et des Télécommunication. The body responsible for European (not
only EC) efficient utilisation of spectrum and regulatory matters
3.2.9
deactivator
a device which changes transponders so that they no longer transpond
3.2.10
electromagnetic coupling
systems using electromagnetic waves (hertzian waves) as a means of transferring data or power are said to
use electromagnetic coupling
3.2.11
electronic article surveillance (EAS)
a system which detects the presence of transponders, which is often used for anti-theft purposes
3.2.12
electrostatic coupling
systems using the induced voltage on a plate as a means of transferring data or power are said to use
electrostatic coupling
3.2.13
ERP
effective radiated power (normally expressed in watts.) is the product of the power supplied to the antenna
and its gain relative to a half-wave dipole in a given direction
3.2.14
EIRP
equivalent isotropic radiated power (normally expressed in watts) is the product of the power supplied to the
antenna and the antenna gain in a given direction relative to an isotropic antenna (absolute or isotropic gain)
3.2.15
frequency
the number of times per second that a signal executes a complete cycle
3.2.16
harmonics
multiples of a principal frequency, invariably exhibiting lower amplitudes
3.2.17
inductive coupling
systems using magnetic fields as a means of transferring data or power are said to use inductive coupling
3.2.18
ITU
International Telecommunication Union. The body responsible for world-wide utilisation of the spectrum
3.2.19
memory card
a read/write or re-programmable tag with the size of a credit card
3.2.20
modulation, amplitude (AM)
data superimposed on a carrier by means of changes in its amplitude
3.2.21
modulation, phase (PM)
data superimposed on a carrier by means of changes in its phase
3.2.22
modulation, frequency (FM)
data superimposed on a carrier by means of changes in its frequency
3.2.23
modulation, frequency shift keyed (FSK)
the transmission of data by switching between two frequencies of carrier
3.2.24
modulation, pulse duration (PDM)
the transmission of data by means of the duration of pulses of a carrier
3.2.25
modulation, pulse position (PPM)
the transmission of data by the position of pulses relative to a reference point
3.2.26
nominal range
the range at which a system will provide reliable operation, taking account of the normal variability of the
environment in which it is used

– 13 – EN 50357:2001
3.2.27
omni-directional
capability of a tag to operate in any orientation
3.2.28
orientation
see alignment
3.2.29
orientation sensitivity
the extent to which range is reduced by non-optimal orientation
3.2.30
passive tags
tags that contain no internal power source. Typically, they derive their power from the carrier signal radiated
by the scanner
3.2.31
penetration
term used to indicate the ability of electromagnetic waves to propagate into or through the body or materials
3.2.32
proximity sensor
a device that detects and signals the presence of a tag at or near the sensor's location
3.2.33
RFID
radio frequency identification
3.2.34
range
the distance at which successful reading and/or writing can be accomplished
3.2.35
read
the decoding, extraction and presentation of data from formatting, control and error management bits sent
from a tag
3.2.36
read rate
the rate at which data is read from a tag expressed in bits or bytes per second
3.2.37
read/write
tags that are capable of having their data repeatedly modified are called read/write tags
3.2.38
reader
a device that activates an adjacent tag and then receives, decodes and verifies the returned data. The
verified data may then be passed via an interface to a host system
3.2.39
tag
the transmitter/receiver pair and data storage contained within a single package is referred to as a tag,
transponder, electronic label, code plate and various other terms
3.2.40
transponder
see tag
4 Measurements and calculations for equipment compliance
This clause provides a three-stage method of emission assessment. It is only necessary to use one of the
three stages (4.1 to 4.3) to demonstrate equipment compliance. The stages vary in complexity and the one
most suitable for the equipment concerned should be used.
Assessments are made either against Basic Restrictions or against derived Reference Levels. Reference
Level parameters are directly measurable and so are used for the simplest assessment method in 4.1. Basic
Restriction parameters provide a more fundamental evaluation of exposure but are difficult or impossible to
measure directly, so calculation, and numerical modelling techniques are required. Assessments against
Basic Restrictions are provided in 4.2 and 4.3, with increasing levels of sophistication and complexity. In 4.2,
the modelling takes account of the non-uniformity of the fields, but not of human tissue. In 4.3, the modelling
also takes account of the non-uniformity of the human tissue and its properties.
Subclause 4.4 contains a method to demonstrate compliance for contact and limb currents. This shall be
used in all cases.
The assessment report shall detail all relevant parameters, which may include:
� ambient temperature and humidity,
� diagram of the measurement points,
� measured levels,
� measured frequencies,
� power adjustment (if applicable),
� measurement uncertainty,
� modulation type,
� ancillary equipment,
� measurement instrumentation,
� modelling parameters.
The concept of “shared error budget” shall apply to measurements and calculations. This means that in all
cases, the actual measured or calculated values shall be used for comparison with appropriate exposure
guidelines. Uncertainty values shall be recorded but shall not be included in the comparison.
Measurement protocols in this standard are defined with respect to the dimensions of a standard person in a
standing position. Measurement protocols for subsets of the population are not defined, as these would
significantly increase the complexity of compliance demonstrations. In addition, many guidelines already
take account of variability associated with more susceptible members of the population, and thus offer
sufficient protection to all members of a population under worst case exposure conditions
4.1 Simple measurements to show compliance with derived reference levels
This subclause describes the method for determining compliance of a system to field strength reference
levels.
Instrumentation used to measure exposure levels should be similar or identical to that defined by IEC 61786
(0-9 kHz) [6] and IEC 61983 (> 9 kHz) [7], where possible. The measuring instrumentation must cover the
frequency range of emissions from the unit under test. In the event that broadband instruments are used the
bandwidth of the instrumentation must cover the range of frequencies emitted. The measuring
instrumentation may have a frequency dependent response that correlates with the limits.
In order to fully characterise the exposure conditions it may be necessary to use several instruments
including broadband meters, oscilloscope or spectrum analyser. If more than one instrument is used, then
care must be taken to ensure that the ranges of the instruments do not overlap resulting in an over
assessment of the levels.
– 15 – EN 50357:2001
Spectral information is required to determine compliance with frequency dependent levels. Measurements
shall be performed using instrumentation capable of measuring relevant frequency domain and time domain
characteristics of the signal. In the case of time domain measurements, it may be necessary to determine
the frequency content to compare with the reference levels
It is necessary to consider the frequency range of the emissions and any time varying modulation. These
must be considered where time averaging of exposure is allowed. It may be necessary to calculate the
instantaneous maximum field strength for comparison with limits for pulsed sources. It may also be
necessary to sum the field level at each frequency in accordance with the appropriate exposure guidelines.
It is important to consider the wavelength of the emissions with respect to the position of the person to
determine whether separate electric and magnetic field measurements are necessary. In the near field, for
example, it may only be necessary to measure magnetic fields.
The measurements shall be carried out to determine the unperturbed field strengths. For electric field
measurements, the presence of the human body can significantly affect the field and the instrumentation
should be mounted on a non-conductive support. It may also be appropriate to use a fibre-optic coupled
remote read-out unit (or similar means of distancing the body of the operator) for some electric field
measurements.
If a power adjustment is available on the unit under test then this should be set to maximum or adjusted
according to the manufacturers setting up instructions. The unit under test should be located at sufficient
distance from nearby objects to ensure that the field is not perturbed.
4.1.1 Direct Measurement to show compliance with Derived Reference Levels
The field strengths shall be measured all around the unit under test at a distance, X, as defined in Table 1.
A preliminary scan may be performed to determine the positions of maximum electromagnetic field at this
distance. The field strength shall be determined either by a vector sum over three orthogonal measurement
axes or by measuring the magnitude from a single measurement aligned to give the maximum reading. The
electromagnetic field at the maximum field positions shall be recorded.
If the emissions from the unit under test comply with derived reference levels at all positions then the
equipment is compliant and no further tests or assessments are necessary, other than those in 4.4.
4.1.2 Spatially Averaged Measurements to show compliance with Derived Reference Levels
In some guidelines, the derived reference levels are based on spatially averaged values over the entire body
of the exposed individual. The following subclause describes a method of deriving an equivalent value for
comparison against such levels.
For the types of equipment covered by this document, the torso is the most appropriate area of the body to
be assessed and the grid in Figure 1a shall be used. The position of the grid in relation to the unit under test
can vary according to the typical usage of the unit. The layout and dimensions of the grid shall remain
identical. In the exceptional cases where the exposure is predominately to the head, then the grid in
Figure 1b must be used. This ensures that a more conservative result is obtained.
The measurement methods as described in the previous subclause shall apply and measurements taken
over the grid patterns defined in Figure 2. The actual grid position used, in relation to the unit under test,
depends on the typical equipment configuration. Other grid positions than those described can be used
provided that the position used is representative of the normal use of the unit.
The measured values at each of the grid points shall be recorded. The arithmetic average of the measured
values should be calculated and compared with the appropriate derived reference levels. This result shall be
recorded also.
For frequencies above 300 MHz and when the measurement is substantially in the far field, measurements
can be taken of E-Field as above.

For both near and far field assessments at microwave frequencies, it is acceptable to use calculated fields
for comparison to reference levels. Several suitable commercial packages are available for modelling field
patterns. The model should initially be validated by one or more comparative field measurements and the
comparison should be within reasonable measurement and modelling uncertainties (see clause 7).
Table 1 – Dimensions and distances for Figures 1 and 2
Figure Normative dimensions Informative dimensions
1)
(cm) (cm)
a/b/c X Z Height Width Depth
General torso grid 1a 15 - 85 - - -
General head grid 1b 10 - 145 - - -
Single floor standing unit 2a 15 20 85 120-160 - 40-80
Dual floor standing units 2b 15 20 85 120-160 70-200 40-80
6)
Single unit in the floor 2c 15 - 85 - 60-100 40-80
Single unit in the ceiling 2d 15 - 85 210-250 60-100 40-80
6)
Dual floor/ceiling units 2e 15 - 85 210-250 60-100 40-80
6)
“Walk- through” unit 2f 15 20 85 210-300 70-300 0,5-50
3)
Counter mounted unit  2g 15 30 85 70-90 20-40 20-40
Wall mounted unit 2h 15 20 - 60-160 20-100 20-50
4) 2
Hand-held unit 2i 15 10 - 70-140 Area: 100-200 cm
1) These dimensions represent the range over which the majority of equipment falls. Some may fall outside the range.
2) The total sum of the size of the head grid, torso grid and Z dimension is 175 cm, which is approximately the height for a standard
person.
3) The X distance represents a typical distance when mounted in a counter top. If operated at closer distances, occupational levels
are most likely to apply.
4) The X distance takes into account the possibility that a hand held device could be used to scan a human body.
5) In the case of equipment not falling into the above categories, it is permissible to use the nearest appropriate category or use a new
configuration using similar principles to those above.
6) Some units are buried a minimum distance below the top surface of the floor. This distance can be added to the Z dimension,
provided the requirement is clearly stated in the installation documentation.
7) The grid positions and dimensions reflect the position of the centre of the probe. The grey circle shows an example of the probe
position with respect to the grid.
8) Some units are circular or oval but approximate dimensions would reflect the rectangular sizes given

– 17 – EN 50357:2001
Figure 1a – Torso measurement grid
Figure 1b – Head measurement grid

Figure 2a – Single floor standing antenna
Figure 2b – Dual floor standing antennae

– 19 – EN 50357:2001
Figure 2c – Single floor antenna
Figure 2d – Single ceiling antenna

Figure 2e – Combined floor & ceiling antennae
Figure 2f – “Walk-through” loop antenna

– 21 – EN 50357:2001
Figure 2g – Horizontal, desk or counter top mounted antenna
Figure 2h – Vertical, wall or frame mounted antenna

Figure 2I – Hand-held antenna
– 23 – EN 50357:2001
4.2 Measurements and analysis to show compliance with basic restrictions
In cases where measured values exceed derived reference levels, compliance may be demonstrated by
comparison against basic restrictions. This can be achieved by simple analytical or numerical modelling as
outlined in the following subclauses.
In assessing compliance, it is important to take into account the spatial non-uniformity of the magnetic fields,
and whether exposure is in the near or far fields.
4.2.1 Modelling and analysis of field non-uniformity up to 30 MHz
This subclause takes account of the non-uniform fields that are normal for the types of equipment covered by
this document at these frequencies. The near field extends for some metres away from the unit so all
assessments are made in the near field.
The fields may be measured using a finer grid than that used in 4.1. The grid size should be commensurate
with the spatial variation of the field, thus allowing realistic interpolation between measurement points.
Field modelling is also an acceptable way to determine complex field patterns. Several suitable commercial
packages are available for this. The model should initially be validated by one or more comparative field
measurements and the comparison should be within reasonable m
...