平成 18 年 1 月
社団法人

ビジネス機械・情報システム産業協会

技術委員会 安全小委員会・電磁環境小委員会 合同
EN50371 対応 WG

電磁界人体ばく露制限規格(EN50371)対応方法の検討結果報告

１．はじめにEU において、低電圧指令（LVD）と通信端末指令（R&TTED）適合評価対象規格として 2004 年に EN50371:2002（Generic standard to demonstrate the compliance of low
power electronic and electrical apparatus with the basic restrictions related to human
exposure to electromagnetic fields (10 MHz - 300 GHz) - General public）が発効し、当該製品においては従来規格に加え EN50371 が適合評価対象規格となった。
しかし、EN50371 では、機器からの無線周波放射電力の評価を行なうことを規定しているが、非意図的放射機器（JBMIA 対象品目）に関しては、具体的な放射電力の測定・評価方法の規定はなく、評価者による 放射電力を決定した方法と根拠 を記録に残すとの規定しかない。
この状況を踏まえ、低電圧指令（LVD）の JBMIA 対象品目（非意図的放射機器）の要求範囲に限定し、当該規格の適切な適合確認手法を見出す為、当 WG を設立し調査研究を行ない、EMI の測定結果を用いて放射電力推定方法を検討したので、ここに審議結果を報告する。
本報告書により、EN50371 対応を理解する一助にしていただきたい。
２．WG メンバー（敬称略）
委員：

水野(主査/リコー)、関澤(副主査/富士写真フイルム)、
竹牟禮(東芝テック)、田路(カシオ計算機)、
杉山(キヤノン)、鈴木(コニカミノルタビジネステクノロジーズ)、
海老塚(富士ゼロックス)、吉岡(松下電器)

オブザーバー： 中丸(リコー)、久保田(コスモス・コーポレイション)、前野(ユーエル エーペックス)
事務局：

漆田(JBMIA)

３．活動期間平成 17 年 4 月〜平成 18 年 1 月

1

４．調査項目(1) EN50371 の検討
EN50371 は、意図的放射、非意図的放射にかかわらず機器からの放射電力等が次の条件を満たしていれば、公衆への電磁界ばく露に関する基本制限を満足すると規定されているが、非意図的機器に関しては、放射電力の評価法について、具体的な記載は何もない。
＜放射電力等の条件＞
平均放射電力：20mW 以下
20×prf ｍＷ未満（300MHz から 10GHz で 30μs 未満のパルス）
prf（パルスの繰返し周波数）：単位時間あたりの発振数(2) EN50371 の適合確認方法（技術ガイドライン）の検討
ドイツから適合確認方法に関する技術ガイドライン ”Technical guideline on theassessment of the Human exposure to electromagnetic fields for Low power electronicand electrical apparatus according to the Standard EN50371:2002”（EN50371 に基づく人体の電磁波ばく露に関する低出力電子電気機器の評価についての技術ガイドライン）が CENELEC/TC106X 委員会に提案されたが、近磁界および垂直方向に対する測定方法の不備等の理由で否決された。本 WG は否決されたことを理解した上で、当該ガイドラインを調査した。
CENELEC/TC106X：EN 規格の制定機関である欧州電気標準化委員会の傘下にある技術委員会で、電磁界の人体ばく露を扱っている。
(3) 関連規格の検討
EN50392:2004(Generic standard to demonstrate the compliance of electronic andelectrical apparatus with the basic restrictions related to human exposure toelectromagnetic fields (0 Hz - 300 GHz))、等

５．検討結果(1) EN50371 の検討結果
EN50371 で宣言するための適用可否判定フローを図１に示す。
＜図１の内容＞① 放出電力測定は可能か？
② ①の測定が可能な場合は EN50371 に適合しているか？
③ EN50371 で評価し、調和規格として適合宣言書に EN50371 を記載する。
④ ①の測定が不可能な場合または EN50371 に不適合の場合は、適合宣言をしない。

2

(2) 技術ガイドラインの検討結果
1) 技術ガイドラインに従って測定する場合のフローを図２に示す。
＜図２の内容＞① 次の規格で、EUT のエミッション測定を行ない、適合しているか？
10MHz−30MHz ：EN55011
30MHz−1GHz ：EN55022
1GHz 以上：FCC Part15, Subpart B（上限は、EUT のクロックに依存）② EN50371 の対象製品である。
③ 置換法もしくは簡易置換法による放射電力の計算値の合計が 20mW 未満であるか？
置換法：

EUT を利得の既知なアンテナに置換え、測定値と同レベルになる
よう信号発生器の出力レベル調整し、その出力レベルから計算により求める。

簡易置換法：試験環境が自由空間の条件を満たす場合は測定値から計算によって求める。
④ ③で 20mW 未満であれば、②と同様。
⑤ ③で 20mW 以上の場合、EN50371 の適合宣言をしない。
2) EN50371 の測定方法の制限事項
技術ガイドライン検討の結果、下記のような測定手法の制限事項を定めないと適合確認が出来ないということが判明した。
＜制限事項＞① 10MHz〜300GHz の全周波数範囲の測定が必要。
② 周波数によって電界強度の測定限界（暗ノイズレベル等）があるので、暗ノイズレベルの規定が必要（これ以下は測定しないというレベル）。
③ 全方位測定（上下方向等）は EMI 試験では実施していないので、真の最大値測定が必要。
(3) EN50392 について
EN50371 に非対象の場合は、EN50392 で評価することになるが、まだ欧州官報に公告されていない。EN50392 でも EN50371 と同様に、非意図的放射機器に対して具体的な評価法の規定はない。

3

６．結

論

EN50371 による適合宣言について
EN50371 で適合宣言するために、当該規格の対象/非対象の判定法として、上記の制限事項があるなど課題は残っているが、現時点では、技術ガイドラインを用いることはできる。
ただし、EN50371 は低出力電子電気機器であれば、公衆への電磁界ばく露に関する基本
制限を満足すると規定しているだけで、適合を強制しているわけではない。
したがって、EN50371 における低出力電子電気機器かどうかが不明である場合は、当該規格の適合を宣言しないことで対応すれば、現時点では妥当であると考える。

７．おわりに
本活動のなかで、技術ガイドライン中の式および数値に関しては精査せず、基本的な考え方を引用した。
今後、EN50392 の官報公告日などの欧州動向を注視しながら、必要に応じて JBMIA
ガイドラインを提案したい。
IEC TC106 の NP（New Work Item Proposal）である 106/106/NP も EN50371 と同じ内容で規格化が検討されはじめたので、規格審議過程での意見提案ができるようになった。

4

LVD 対象機器

No① 放出電力測定
は可能か？
Yes

No

② EN50371 に適合しているか*1 判定条件
放出ピーク電力：
20W 未満平均放出電力：20mW 以下
20×prf mW 未満（300MHz から 10GHz で 30μs 未満のパルス）

Yes

prf（パルスの繰り返し周波数）：単位時間あたりの発振数④ 適合宣言をしない③ 調和規格として
EN50371 を記載する

図１．EN50371 適用可否判定フロー5

※

LVD 対象機器

10MHz−30MHz ：EN55011
30MHz−1GHz ：EN55022
1GHz 以上：FCC Part15 Subpart B

No①EUTYesの
エミッション規格に適合
しているか
Yes

No

③置換法
もしくは簡易置換法からの計算値<20mW

Yes②,④ EN50371 で適合宣言⑤ EN50371 で適合宣言をしない

図２．技術ガイドライン適用フロー

6

Technical Guideline

No.: 2005002

Standard / Regulation:

Subject:

Status:EN 50371:2002

Assessment method for EN 50371

Revision:

Sub-clause / Issue:

Key words:

EMF

EMF, Class A, Substitution Method, 20mW

Final of 2005-0511
1.0

CONTENT
Technical guideline on the assessment of the Human exposure toelectromagnetic fields for Low power electronic and electrical apparatus
according to the Standard EN 50371:2002
1.
2.
3.
3. 1
3.2
3.3
3.4
3.5
4
4.1
4.2
4.3
5
5.1
5.2
5.3
6
7

Introduction.................................................................................... 2
Scope of the guideline .................................................................. 2
Assessment methods.................................................................... 2
Assessment of total input power ................................................. 3
Assessment of average power of pulses .................................... 3
Assessment of Peak power (to be < 20 W) .................................. 3
Assessment of emitted power through reference
to other product standards ........................................................ 3
Assessment of the total of emitted power in the formof Electromagnetic fields (to be < 20 mW) .................................. 3
Determination of the Radiated power of the EUT by using theSubstitution Method ...................................................................... 4
Principle of setup........................................................................... 4
Principle of substitution measurement..................................... 4
Determination of the Radiated power of the EUT by using
Simplified Substitution method.................................................... 7
Application of the Substitution method to determine the total
emitted power ................................................................................ 10
Determination of the emitted power between
10 MHz and 30 MHz........................................................................ 18
Determination of the emitted power between
30 MHz and 1 GHz.......................................................................... 21
Determination of the emitted power > 1 GHZ ......................... 21
Consideration of measurement uncertainties............................. 23
Annex: example assessment........................................................ 23
Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 1 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

1

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Introduction
With the publication of the Council recommendation
1999/519/EC, aiming to attain a high level of health protection,
basic restrictions and reference levels for electric, magnetic andelectromagnetic fields are proposed which are based on theinternationally recognized ICNIRP recommendations.
In the subsequent standardisation mandate M/305 Sept. 2000
addressed to CEN, CENELEC and ETSI, the development foradequate harmonised standards for purpose of presumptionof conformity was initiated. This mandate stipulates : “in case of
Products likely to emit very weak EMF, a description of simpler
and less accurate measurement methods and/or measurement
equipment can be made providing the uncertainties by using
such equipment or measurement method are fully taken into
account.
Based on above principles the Generic standard EN 50371:2002
addresses such products.
This document is intended to provide adequate guidance for
product design, manufacturing and test-laboratories forpractical assessment methods to demonstrate the complianceand evaluation of uncertainties.

2

Scope of the guideline
the Guideline is addressing the technical assessment for EMF
according to the CENELCE standard EN 50371 for Low power
emitting devices with a total of max 20mW radiated power.
For technical reasons, the measurement methods are divided in
3 groups:a) 10 MHz – 30 MHzb) 30 MHz – 1 GHZc) > 1 GHz

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

3 Assessment methods

3. 1 Assessment of total input power= to be amended =3.2 Assessment of average power of pulses= to be amended =3.3 Assessment of Peak power (to be < 20 W)= to be amended =3.4 Assessment of emitted power through reference
to other product standards= to be amended =3.5 Assessment of the total of emitted power in the formof Electromagnetic fields (to be < 20 mW)
The following chapter 4 details the assessment method which will
provide evidence that the apparatus under evaluation will not emit a
total of radiated power above 20 mW.
The practical assessment of an low power apparatus will include 2
steps, where in the 1st step the radiated Power will be evaluated bya field strength measured followed in a 2nd step by the application of
the substitution method where necessary.

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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Form guide2004-1.

Technical Guideline
EN 50371:2002;

4

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Determination of the radiated power of the EUT by using
Substitution Method

4.1 Principle of

the

setup

Anechoic
Chamber
1. EUT
2. Substitution
Antenna

Receiving
Antenna

Receiver
ShieldedRoomIN

4.2 Principle of substitution

SignalGenerator
OUT

measurementa) Measure each significant emission (maximising emission levelby rotating turntable, moving receiving antenna 1m -4m in height(where applicable ) of the EUT and record the receiver reading. An
Emission is classified as “significant” taking into account thefollowing criteria:
quantity and amplitude of Emissions is assessedagainst the values in table 1 and leads to the conclusion that the total
radiated power may exceed 10 mW
Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mWb) Replace the EUT by an antenna with known gain and adjust thesignal generator output level to the same receiver level for each
emission as previously determined in a)c) The radiated power of the EUT is then determined by the formulasin c1) and c2):c1) Measurement of EUT
Transmission Path loss

Receiver/Spectrum
analyser

EUT

D (3m, 10m)

EIRP
A

=

Att Path

EIRP
AttPath:Effective Isotropic Radiated Power of the EUT

Gri

:
:

Acr
Pr

:
:

Path loss of the transmission distance (3m or 10m)
Gain of the receiving antenna (calibrated as isotropic
gain )
Attenuation of coaxial receiving signal cable
Received power at the input of the Receiver/Spectrum
Analyser

+

-

Gri

+

P

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 5 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mWc2) Substitution of the EUT
After measuring the emissions of the EUT, the EUT is removed anda substitute antenna is placed instead of the EUT at the same heightand same distance from receiving antenna. For each frequency
under measurement the signal Generator level is adjusted to obtain thesame reading level as recorded before as EUT emission level.

Transmission Path loss

Receiver/Spectrum
analyserSG

D (3m, 10m)

SG
+

-

Atr

A

+
+

Gtr

=

Att Path

-

Gri

P

SG
Atr

:

Signal Generator output level

:

Gtr

:

AttPath:Attenuation of the cable between SG and transmit
antennaGain of the transmitting antenna (calibrated as
isotropic gain )Path attenuation of the transmission distance (3m or
10m)Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Gri

:

Acr
Pr

:
:

Gain of the receiving antenna (calibrated as isotropic
gain )
Attenuation of coaxial receiving signal cable
received power at the input of the Receiver/Spectrum
Analyser

The resulting value for the EIRP for each individual emitted frequency
can be calculated by the following formula:
EIRP = SG - Atr + Gtr [ Eq 1]
If ERP (Reference is λ/2 dipol as transmit antenna) is being used as
reference:
ERP = EIRP- 2.15 dB.

[ Eq 2]Further details on the substitution method can be found in 7.2.3 of ETSITR 102273-2 V1.2.1 (2001-12) and ETSI TR 102273-3 V1.2.1 (2001-12)
4.3 Determination of the radiated power of the EUT by using
simplified substitution method

theNote: The simplified substitution method can only be applied, when thefollowing conditions are fulfilled:••

The measurement environment (Fully Anechoic Chamber) must provide
free space environment in terms of electromagnetic radio wave
propagation
The measurement distance d must meet far field conditions: d ≥λ/2π

When the simplified substitution method is applied, the EIRP can be
determined by calculation only , when path loss, gain of the receiving
Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

antenna, and cable loss of the Coaxial cable between receiving antenna
and Receiver /Spectrum Analyser are known.
The EIRP can then be calculated as follows:
EIRP

Gri

+

4.3.1 Determination of free space path attenuation(Att Path)A=

Att PathP+-[ Eq 3]

The free space path attenuation is defined at the ratio between thetransmitted power and the power received at a distance (d):PtPr

= ( 4( Cπ df) 2) ⇒ 10 log Prt = 20 log( C4 π0 ) + 20 log d + 20 log f [Eq 4]
0
2P

this equals if distanced is in [ m ] and frequency f is in [ MHz ]Att path = − 27 ,56 + 20 log d + 20 log f:[ Eq 5]and if distance is in [ m ] and frequency f is in [ GHz ]Att path = 32 , 44 + 20 log d + 20 log f[ Eq 6]

For a measurement distances of 3 m and 10 m the resulting pathattenuation is:
Frequency/GHz

Path attenuation/ dB
distance d = 3m

Path attenuation/dB
Distance d = 10m

0.03

11.52

21.98

0.05

15.96

26.42

0.1

21.98

32.44

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

0.2

28.00

38.46

0.3

31.52

41,98

0.6

37.54

48,00

0.8

40.04

50.50

1.0

41.98

52,44

2.0

48.00

58,46

3.0

51.52

61.98

4.0

54.02

64,48

6.0

57.54

68.00

8.0

60.04

70.50

10.0

61.98

72,44

12.0

63.56

74,02

15.0

65.50

75,96

20.0

68.00

78.46

25.0

69.94

80.40

30.0

71.52

81.98

Example:The EUT emission is measured at 200 MHz,the Receiver input signal is indicated as -57 dBm, the measurement
distance is 3 m.
Pr :- 57 dBm
Acr:
2.5 dB
3.5 dBGri:
Att Path:
28 dB
EIRP
A

=
+

Att Path
P

-

Gri

+

EIRP = -30dBm

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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EN 50371:2002;

5

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Application of the substitution method to determine the total
emitted power

As worst case condition it is assumed that the EUT is emitting it’sradiated power throughout the frequency range as considered in EN
50371 between 10 MHz and 300 GHz as broadband spectrum continuous
wave exactly on the limits (Class A) as given in the relevant EMC
standards :Fieldstength [dBµV/m] limits for the assessment of Radiated Interference
Emissions according to commonly used EMC standards Class A limits
80
dB
µV/
m

79.5
dBµV/m

70

d)

dB
µV/
m

57

a1)
50
a2)

dBµV/mdBµV/m
c)

b)

10

30

230

1000 MHz

Frequency

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

300 GHz
Page 10 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

The frequency band to be considered in EN 50371 is not covered by theradiated emission requirement of a single EMC standard. The above limits
are a combination of the following commonly applied EMC standards:a) EN 55011:2003 +A1:2004 Table 5a : measurement distance: 3m;
10 MHz to 20 MHz
limit:
D 80 [dbµV/m](a1)
20 MHz to 30 MHz
limit:
D 70 [dbµV/m](a2)b) and c) EN 55022:1998 Table 5:30 MHz to 230 MHz
limit:

measurement distance: 3m;
D 50 [dbµV/m](b)

230 MHz to 1000 MHZ

D 57[dbµV/m]

limit:(c)d) FCC Part 15 Subpart B (2003) measurement distance 3m class A limits> 1000 MHz:limit:
D79,5 [dbµV/m](d)Then the total of radiated power is assessed under the following
theoretical assumptions: The EUT radiates equally distant spectral lines
as follows:
Then the total of radiated power is assessed under the following
theoretical assumptions: The EUT radiates equally distant spectral
lines as follows:

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Spectral line distance ds

In Band a1) 10 MHz to 20 MHz the Receiver (CISPR) Resolution bandwidthof 9kHz and the spectral line distance ds = 6 kHz leads to a the following
maximum number of spectral lines:

20MHz − 10MHz= 1667[Spectral _ Lines ]6kHz

In Band a2) 20 MHz to 30 MHz the Receiver (CISPR) Resolution bandwidthof 9kHz and the spectral line distance ds = 6 kHz leads to a the following
maximum number of spectral lines:

30MHz − 20 MHz= 1667[Spectral _ Lines ]6kHzSony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 12 of 23

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EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

in the Bands b) and c) 30 MHz to 230 MHz and 230 MHz to 1000 MHz
measured with a Receiver (CISPR) Resolution bandwidth of 120kHz aspectral line distance ds =100 kHz
which results in a total of :230MHz − 30MHz= 2000[Spectral _ Lines ]100kHzand

1000MHz − 230MHz= 7700[Spectral _ Lines ]100kHzin the Bands d) 1GHz to 300 GHz measured with a Receiver (CISPR)
Resolution bandwidth of 1MHz a spectral line distance ds =700 kHz
which results in a total of :300GHz − 1GHz
= 427143[Spectral _ Lines ]700kHzUnder this assumption, over the whole frequency band from 10 MHz to
300 GHz the total power of 440377 Spectral lines has to be determined.
The radiated power is to be determined

as follows:n

PTotal = ∑ PSL[ Eq 7]1PSL=

EIRP of a single Spectral linen = total No of Spectral lines

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 13 of 23

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Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

EMC measurements provide electrical field strength measured at a given
distance from the source of radiation. The relationship between Field
strength and Source power is as follows:
E=

1
2r

Ps × Z 0 × 1.64π

[ Eq 8]The above equation is valid for far field free space conditions . The
electrical field strength Er is the field strength present in a distance r
from a RF power source.
Here the RF power is given as ERP through dissipation by a λ/2 Dipole
which has a numeric gain of 1.64.
When radiated EMC measurements are performed above a metallic
ground plane, both direct and reflected RF wave reach the receiving
antenna. By 360 deg. rotation of the EUT and positioning the Receiving
antenna between 1m and 4 m height, attempt is made to maximise fieldstrength. In Phase adding of both waves can lead to an increase of
Field strength of up to 6 dB compared to free space conditions.

For the further analysis this is neglected, which results in a positive
uncertainty margin.
Then the logarithmic equation for the determination of the substituted
ERP is:3
[ Eq 9]PERP = E r − 7.4 − 20 × log r

PERP as[ dBpW ], Er as [ dBµV/m], distance r in [ m]Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 14 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

And if reference is EIRP:[ Eq 2] in [ Eq 9]
3
PEIRP = E r − 5.25 − 20 × log r[ Eq 10]

The following table 1 shows the result at a given distance r of 3 m.
Table 1
Band a1)
10 – 20MHz
EMC limit(dBµV/m)PEIRP
perSpectral line
(dBpW)PEIRP
per
Spectral line(mW)
number ofspectral lines
Total Power
inside Band(mW)
Total Power
inside Band
(dBm)

With [ Eq 7]Band a2)
20 –30MHzBand b)30 – 230
MHz

Band c)230-1000
MHzBand d)1 – 300
GHz

80

70

50

57

79.5

74.25

64,75

44.75

51.75074,25

0.02660.002990.0000299

0.0001496

0.0266

1666

1667

2000

7700

427143

44,32

4.977

0.0597

1.152

11365

16.47

6.97

-12.240.615

40.556the maximum total radiated power(P EIRP)

is:440177

PTotal = ∑ PSL = ∑ Pa ) + Pb ) + Pc ) + Pd ) = 11415.5 mW
1This is approximately 500 times the 20 mW limit. At first it seems notpossible to confirm that the ICNRP limits are met if the unintentionalradiation of an electronic apparatus meets the class A limit.

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 15 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

However the total Radiated power of approx 12 W is only reached under
the assumption that the Apparatus would emit 440177 Frequencies
exactly on the Class A Limit, which is a huge over estimation.
A more realistic approach would be as the worst-case assumption
follows:
In each of the 5 bands (a1, a2, b,c,d) there are 5 frequencies emitted which
would reach the Class A Limit:
The total emitted power would then sum up as shown in table 2

Table 2
Band a1)
10 – 20MHz
EMC limit(dBµV/m)PEIRP
perSpectral line
(dBpW)PEIRP
per
Spectral line(mW)
number ofspectral lines
Total Power
inside Band(mW)
Total Power
inside Band
(dBm)

With [ Eq 7]Band a2)
20 –30MHzBand b)30 – 230
MHz

Band c)230-1000
MHzBand d)1 – 300
GHz

80

70

50

57

79.5

74.25

64,75

44.75

51.75074,25

0.02660.002990.0000299

0.0001496

0.0266

20

20

20

20

20

0,532

0.05980.000598

0.00299

0.532

-2.74

-12.323-32.24-25.243-2.74

the maximum total radiated power(P EIRP)

is:440177

PTotal = ∑ PSL = ∑ Pa ) + Pb ) + Pc ) + Pd ) = 1.127 mW
1Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 16 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Under this more realistic Emission assumption the total radiated Power
would decrease to 1/20 of the EMF limit. Even this assumption is anoverestimation as all the frequencies are radiated in different directions
and will never reach at the same time any 10 g of human tissue.
Conclusion: for the demonstration of Compliance with EN 50371 it isnecessary to measure the Radiated Electromagnetic Emissions in thefrequency range between 10 MHz to 40 (300 at later stage) GHz and makean assessment to demonstrate that the total radiated power fulfils the 20
mW limits.
Based on above results a practical product assessment can be
performed in the following steps:
1) Assess the EUT radiated emissions by electric field strength
measurements and compare with the limits:
Fieldstength [dBµV/m] limits for the assessment of Radiated Interference
Emissions according to commonly used EMC standards Class A limits
80
dB
µV/
m8

0
dB
µV/
m

79.5
dBµV/m

70

d)

dB
µV/
m

57
50

a2)

a1)

dBµV/mdBµV/mc)b)Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 17 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

If all the frequencies measured are within the limits and anengineering analysis according to the number of measured
emissions shows that the total of radiated power is clearly below
the 20 mW limit, compliance with EN 50371 can be concluded
without the need of substitution measurements.
2) If the limits as shown above are exceeded, for thesefrequencies the radiated power has to be evaluated by thesubstitution (simplified substitution, if the site fulfils free spaceconditions). Then the total power of theses frequencies has to be
determined. If result shows total radiated Power is less than 20mW taking into account measurement uncertainties, compliancewith EN 50371 can be concluded.
3) If the total of radiated power is ≥ 20 mW
assessed according to EN 50392.

the product has to be

Details for the measurement method as applicable for therespective frequency bands are as follows:
5.1

Measurement method for the determination of the emitted power
between 10 MHz and 30 MHz (band a1, a2)•

The Measurement distance d must meet far field
conditions:c0λd≥[ Eq 11]=2×π
f × 2×π

as the lowest frequency is 10 MHz, the corresponding minimum
distance is: d ≥ 4.77 m (if level of emission is very low, a shorter
distance e.g. 3 m may be used to make the EUT emissions visible
out of the intrinsic system noise level)Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 18 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Then the limit for each spectral line in this band has to be adjusted
according to the distance of 4.77m:

E ( d ) = E ( 3m ) + 20 × log

Limit(4.77m) =

•
•

•

3m
d

[ Eq 12]50.47 dBµV/m

The Receiver Bandwidth is 9 kHz (acc. To CISPR 16,
using peak detector )The EUT has to be set up for table top equipment, floor
standing equipment and combinations of table top andfloor standing equipment according to the appropriate
applicable product standards e.g. EN 55022, EN 55013.
The maximum emission has to be detected by rotating
the table with the EUT or the floor standing equipmentby 360 degrees. The receiving loop antenna has to berotated as well to maximise the measured field strength foreach measured frequency respectively.
• In order to determine the substituted power according to
the procedure described in 4.1, the EUT has to be
replaced by a transmitting loop antenna at the same
distance d.

• The same procedure (field measurement andSubstitution) has to be repeated vertical polarisedradiation (transmitting and receiving loop antenna arepositioned parallel to the ground plane)

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 19 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Transmission Path loss

Receiver/Spectrum
analyserSG
1m above
grond
plane

80cm

D (4.77m)
SG
+

P

Atr

+

Gtr

=

Att Path

-

Gri

+

Acr

The EIRP can then be determined using [ Eq 1]:

EIRP = SG - Atr + Gtr
The isotropic gain Gtri of the transmitting antenna can be

determined from its E-field antenna factor by the following
formula:AFE = 20 × log f − Gtri − 29.78[ Eq 13]

if the H-Field antenna factor is provided, the E-Field antenna
factor can be determined by:
AFE = AFH + 20 × log(120π ) = AFH + 51.5dB[ Eq 14]

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 20 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

5.2

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Measurement method for the determination of the emitted power
between 30 MHz and 1GHz (band b, c):

•

•
•

•

•

•

5.3

No.: 2005002

The measurement distance is 3 m. If larger distances areused, the E-Field limit has to be adjusted by using[ Eq
12]
The receiver bandwidth is 120 kHz ( acc. to CISPR 16,
using Peak detector)
The EUT has to be set up for table top equipment, floor
standing equipment and combinations of table top andfloor standing equipment according to the appropriate
applicable product standards e.g. EN 55022, EN 55013.
The procedure to determine maximum of emission is torotate turntable be 360 deg and moving receiving
antenna between 1m and 4 m (horizontal and verticalpolarisation)
The determination of the Substitution power is done
following the procedures of 4.1
Usually EMC product standards require the assessmentof the radiated emissions between 30 and 1000 MHz .
And compliance with these limits has been demonstrated
by measurements. These results can be used also for
EMF assessment according to EN 50371 without theneed to repeat the measurements.

Measurement method for the determination of the emitted power
for frequencies above 1 GHz (band d):Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 21 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW•

The measurement distance is 3 m. If larger distances
are used, the E-Field limit has to be adjusted by using[ Eq 11]••••

The receiver bandwidth is 1 MHz ( acc. to CISPR 16,
using peak detector)
The EUT has to be set up for table top equipment, floor
standing equipment and combinations of table top andfloor standing equipment according to the appropriate
applicable product standards e.g. EN 55022, EN 55013.

The procedure to determine maximum of emission is torotate turntable be 360 deg and moving receiving
antenna between 1m and 4 m (horizontal and verticalpolarisation).
The determination of the Substitution power is done
following the procedures of 4.2

Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

Page 22 of 23

Form guide2004-1.

Technical Guideline
EN 50371:2002;

6

No.: 2005002

Assessment method for EN 50371; EMF, Class A, Substitution Method, 20mW

Consideration of measurement uncertainties

6.1
Uncertainties for field strength measurements using (broadband)receiving antennas and Spectrum Analyser/Receiver:

The above table is an example only and needs to be modified according to
the actual testing environment being used to perform the EMF
measurements.

6.2
Uncertainties for the substitution measurement where EUT is
replaced by calibrated transmit antenna=== to be amended===7

Annex: example assessment=== to be amended ===Sony Deutschland GmbH; PCE, Hedelfinger Strasse 61, D-70327 Stuttgart

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Form guide2004-1.