Ultrasonics - Power measurement - High intensity therapeutic ultrasound (HITU) transducers and systems

IEC 62555:2013 establishes general principles relevant to HITU fields for the use of radiation force balances in which an obstacle (target) intercepts the sound field to be measured; specifies a calorimetric method of determining the total emitted acoustic power of ultrasonic transducers based on the measurement of thermal expansion of a fluid-filled target; specifies requirements related to the statement of electrical power characteristics of ultrasonic transducers; provides guidance related to the avoidance of acoustic cavitation during measurement; provides guidance related to the measurement of HITU transducers of different construction and geometry, including collimated, diverging and convergent transducers, and multi-element transducers; provides guidance on the choice of the most appropriate measurement method; and provides information on assessment of overall measurement uncertainties. This International Standard is applicable to the measurement of ultrasonic power generated by HITU equipment up to 500 W in the frequency range from 0,5 MHz to 5 MHz. HITU equipment may generate convergent, collimated or divergent fields. For frequencies less than 500 kHz, no validations exist and the user should assess the uncertainties of the power measurement and measurement system at the frequencies of operation. This International Standard does not apply to ultrasound equipment used for physiotherapy, for lithotripsy for general pain relief.

Ultraschall - Leistungsmessung - Hochintensive, therapeutische Ultraschallwandler und -systeme (HITU)

Ultrasons - Mesurage de puissance - Transducteurs et systèmes ultrasonores thérapeutiques de haute intensité (HITU)

La IEC 62555:2013 établit les principes généraux, applicables aux champs HITU, permettant d'utiliser les balances de forces de rayonnement dans lesquelles un obstacle (cible) intercepte le champ acoustique à mesurer; spécifie une méthode calorimétrique de détermination de la puissance acoustique totale émise par des transducteurs ultrasonores, en se fondant sur le mesurage de la dilatation thermique d'un fluide cible; spécifie les exigences relatives à la déclaration des caractéristiques de la puissance électrique des transducteurs ultrasonores; fournit des recommandations permettant d'éviter la cavitation acoustique au cours du mesurage; donne des lignes directrices pour le mesurage des transducteurs HITU de différentes constructions et géométries, y compris les transducteurs non focalisants, divergents et focalisants ainsi que les transducteurs à éléments multiples; fournit des recommandations quant au choix de la méthode de mesurage la plus appropriée; et fournit des informations concernant l'évaluation des incertitudes de mesure globales. La présente Norme Internationale s'applique au mesurage de la puissance ultrasonore générée par des appareils HITU, atteignant jusqu'à 500 W, dans la gamme des fréquences de 0,5 MHz à 5 MHz. Les appareils HITU peuvent générer des champs focalisés, non focalisés ou divergents. Il n'existe aucune validation pour les fréquences inférieures à 500 kHz. Il convient que l'utilisateur évalue les incertitudes de mesure de la puissance et du système de mesure aux fréquences de fonctionnement utilisées. La présente Norme internationale ne s'applique pas aux appareils à ultrasons utilisés pour la physiothérapie, pour la lithotritie ou pour soulager la douleur de manière générale.

Ultrazvok - Merjenje moči - Merjenje izhodne moči visokointenzivnih terapevtskih ultrazvočnih (HITU) pretvornikov in sistemov (IEC 62555:2013)

Standard EN-IEC 62555 uvaja splošna načela, pomembna za polja HITU, za uporabo ravnotežij sil sevanja, pri katerih ovira (tarča) prestreže zvočno polje, ki je predmet meritve; - določa kalorimetrično metodo za določanje skupne oddane akustične moči ultrazvočnih pretvornikov glede na merjenje toplotnega raztezanja tarč, napolnjenih s tekočino; - določa zahteve, povezane z izjavo o lastnostih električne moči ultrazvočnih pretvornikov; - nudi navodila, povezana s preprečevanjem akustične kavitacije med meritvijo; - nudi navodila, povezana z meritvijo pretvornikov HITU različnih oblik in sestavljenih na različne načine, vključno s kolimiranimi, divergentnimi in konvergentnimi pretvorniki; - nudi navodila glede izbire najbolj primerne meritvene metode; - nudi informacije glede ocenjevanja merilnih negotovosti. Ta mednarodni standard velja za merjenje ultrazvočne moči do 500 W v frekvenčnem območju od 0,5 MHz do 5 MHz, ki jo proizvaja oprema HITU. Oprema HITU lahko proizvaja konvergentna, divergentna ali kolimirana polja. Za frekvence, nižje od 500 kHz, ni preverjenih meritev, in uporabnik mora oceniti merilne negotovosti postopka merjenja moči in meritvenega sistema pri delovnih frekvencah. Ta mednarodni standard se ne uporablja za: - ultrazvočno opremo, ki se jo uporablja pri fizioterapiji za postopek litotripsije, ki blaži bolečine.

General Information

Status
Published
Publication Date
24-Apr-2014
Technical Committee
Drafting Committee
Current Stage
6060 - Document made available
Due Date
24-Mar-2014
Completion Date
25-Apr-2014

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SLOVENSKI STANDARD
SIST EN 62555:2014
01-junij-2014
8OWUD]YRN0HUMHQMHPRþL0HUMHQMHL]KRGQHPRþLYLVRNRLQWHQ]LYQLKWHUDSHYWVNLK
XOWUD]YRþQLK +,78 SUHWYRUQLNRYLQVLVWHPRY ,(&
Ultrasonics - Power measurement - Output power measurement for high intensity
therapeutic ultrasound (HITU) transducers and systems
Ultrasons - Mesurage de puissance - Transducteurs et systèmes ultrasonores
thérapeutiques de haute intensité (HITU)
Ta slovenski standard je istoveten z: EN 62555:2014
ICS:
17.140.50 Elektroakustika Electroacoustics
SIST EN 62555:2014 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 62555:2014
---------------------- Page: 2 ----------------------
SIST EN 62555:2014
EUROPEAN STANDARD
EN 62555
NORME EUROPÉENNE
April 2014
EUROPÄISCHE NORM
ICS 17.140.50
English version
Ultrasonics -
Power measurement -
High intensity therapeutic ultrasound (HITU) transducers and systems
(IEC 62555:2013)
Ultrasons - Ultraschall -
Mesurage de puissance - Leistungsmessung -
Transducteurs et systèmes ultrasonores Messung der Ausgangsleistung für
thérapeutiques de haute intensité (HITU) hochintensive, therapeutische
(CEI 62555:2013) Ultraschallwandler und -systeme
(IEC 62555:2013)

This European Standard was approved by CENELEC on 2013-12-24. 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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,

the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,

Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2014 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 62555:2014 E
---------------------- Page: 3 ----------------------
SIST EN 62555:2014
EN 62555:2014 - 2 -
Foreword

The text of document 87/538/FDIS, future edition 1 of IEC 62555, prepared by IEC TC 87 "Ultrasonics"

was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 62555:2014.

The following dates are fixed:
• latest date by which the document has (dop) 2014-10-25
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2016-12-24
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent

rights.
Endorsement notice

The text of the International Standard IEC 62555:2013 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 62127-2 NOTE Harmonized as EN 62127-2
IEC 60601-2-62 NOTE Harmonized as EN 60601-2-62
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SIST EN 62555:2014
- 3 - EN 62555:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 61161 2013 Ultrasonics - Power measurement - Radiation EN 61161 2013
force balances and performance requirements
IEC/TR 62781 Ultrasonics - Conditioning of water for - -
ultrasonic measurements
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SIST EN 62555:2014
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SIST EN 62555:2014
IEC 62555
Edition 1.0 2013-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Ultrasonics – Power measurement – High intensity therapeutic ultrasound (HITU)
transducers and systems
Ultrasons – Mesurage de puissance – Transducteurs et systèmes ultrasonores
thérapeutiques de haute intensité (HITU)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XA
ICS 17.140.50 ISBN 978-2-8322-1163-2

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN 62555:2014
– 2 – 62555 © IEC:2013
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 8

4 List of symbols .............................................................................................................. 11

5 Power measurement for HITU equipment....................................................................... 12

6 Radiation force on a target ............................................................................................ 13

6.1 General ............................................................................................................ 13

6.2 Requirements for equipment ............................................................................ 14

6.2.1 Target type ..................................................................................... 14

6.2.2 Target diameter .............................................................................. 15

6.2.3 Balance / force measuring system .................................................. 15

6.2.4 System tank .................................................................................... 15

6.2.5 Target support structures ................................................................ 15

6.2.6 Transducer positioning ................................................................... 15

6.2.7 Anti-streaming foils ......................................................................... 15

6.2.8 Transducer coupling ....................................................................... 16

6.2.9 Calibration and stability .................................................................. 16

6.3 Requirements for measuring conditions ........................................................... 16

6.3.1 Lateral target position ..................................................................... 16

6.3.2 Transducer/target separation .......................................................... 16

6.3.3 Water ............................................................................................. 16

6.3.4 Water contact ................................................................................. 17

6.3.5 Environmental conditions ................................................................ 17

6.3.6 Thermal drifts ................................................................................. 17

6.4 Measurement uncertainty ................................................................................. 17

6.4.1 General .......................................................................................... 17

6.4.2 Non-planar ultrasound field ............................................................. 17

6.4.3 Balance system with target suspension........................................... 17

6.4.4 Linearity and resolution of the balance system ................................ 17

6.4.5 Extrapolation to the moment of switching the ultrasonic

transducer ...................................................................................... 18

6.4.6 Target imperfections ....................................................................... 18

6.4.7 Reflecting target geometry .............................................................. 18

6.4.8 Lateral absorbers in the case of reflecting target

measurements ................................................................................ 18

6.4.9 Target misalignment ....................................................................... 18

6.4.10 Ultrasonic transducer misalignment ................................................ 18

6.4.11 Water temperature .......................................................................... 18

6.4.12 Ultrasonic attenuation and acoustic streaming ................................ 19

6.4.13 Foil properties ................................................................................ 19

6.4.14 Finite target size ............................................................................. 19

6.4.15 Environmental influences ................................................................ 19

6.4.16 Excitation voltage measurement ..................................................... 19

6.4.17 Ultrasonic transducer temperature .................................................. 19

6.4.18 Nonlinearity .................................................................................... 19

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SIST EN 62555:2014
62555 © IEC:2013 – 3 –

6.4.19 Other sources ................................................................................. 19

6.5 Calculation of output power .............................................................................. 20

7 Buoyancy change of a target ......................................................................................... 20

7.1 General ............................................................................................................ 20

7.2 Requirements for equipment ............................................................................ 21

7.2.1 Target type ..................................................................................... 21

7.2.2 Entry window diameter .................................................................... 22

7.2.3 Balance / force measuring system .................................................. 22

7.2.4 System tank .................................................................................... 22

7.2.5 Target support structures ................................................................ 22

7.2.6 Transducer positioning ................................................................... 22

7.2.7 Anti-streaming foils ......................................................................... 22

7.2.8 Transducer coupling ....................................................................... 23

7.2.9 Calibration ...................................................................................... 23

7.3 Requirements for measuring conditions ........................................................... 23

7.3.1 Lateral target position ..................................................................... 23

7.3.2 Transducer/Target separation ......................................................... 23

7.3.3 Water ............................................................................................. 23

7.3.4 Water contact ................................................................................. 24

7.3.5 Environmental conditions ................................................................ 24

7.3.6 Thermal drifts ................................................................................. 24

7.4 Measurement uncertainty ................................................................................. 24

7.4.1 General .......................................................................................... 24

7.4.2 Buoyancy sensitivity ....................................................................... 24

7.4.3 Non-planar ultrasound field ............................................................. 24

7.4.4 Balance system including target suspension ................................... 24

7.4.5 Linearity and resolution of the balance system ................................ 24

7.4.6 Curve-fitting and extrapolation ........................................................ 25

7.4.7 Water temperature .......................................................................... 25

7.4.8 Ultrasonic attenuation and acoustic streaming ................................ 25

7.4.9 Foil properties ................................................................................ 25

7.4.10 Finite target size ............................................................................. 25

7.4.11 Environmental influences ................................................................ 25

7.4.12 Excitation voltage measurement ..................................................... 25

7.4.13 Ultrasonic transducer temperature .................................................. 26

7.4.14 Nonlinearity .................................................................................... 26

7.4.15 Other sources ................................................................................. 26

7.5 Calculation of output power .............................................................................. 26

8 Electrical characteristics ................................................................................................ 26

8.1 Electrical impedance ........................................................................................ 26

8.2 Radiation conductance ..................................................................................... 26

8.3 Efficiency ......................................................................................................... 27

Annex A (informative) Other measurement methods ............................................................ 28

Annex B (informative) Target size ........................................................................................ 29

Annex C (informative) Formulae for radiation force .............................................................. 31

Annex D (informative) Expansion method ............................................................................ 36

Annex E (informative) Influence of attenuation and acoustic streaming on determining

incident and output powers ................................................................................................... 42

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SIST EN 62555:2014
– 4 – 62555 © IEC:2013

Annex F (informative) Avoidance of cavitation ...................................................................... 45

Annex G (informative) Transducer efficiency ........................................................................ 46

Bibliography .......................................................................................................................... 54

Figure 1 – Linearity check: balance readout as a function of the input quantity ..................... 20

Figure C.1 – Correction factor of plane wave for the acoustic field of a circular plane

piston ultrasonic transducer as a function of the product of the circular wavenumber

and transducer radius ........................................................................................................... 33

Figure D.1 – Schematic diagram of an expansion target. ...................................................... 36

Figure D.2 – Example of weight vs time sequence ................................................................ 37

Figure D.3 – Time history of the apparent mass of the castor oil target at different

frequencies following an insonation of approximately 1 W acoustic power for a period

of 10 s .................................................................................................................................. 40

Figure G.1 – Electrical voltage source under different loading conditions .............................. 52

Figure G.2 – Electrical voltage source and electrical matching network and transducer

equivalent circuit ................................................................................................................... 52

Figure G.3 – Diagram illustrating electrical loss. ................................................................... 53

Table D.1 – Selected properties of Acros® Organics castor oil in the range 10 °C to

60 °C .................................................................................................................................... 39

Table D.2 – Absorption coefficient of castor oil as a function of temperature ......................... 41

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SIST EN 62555:2014
62555 © IEC:2013 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – POWER MEASUREMENT –
HIGH INTENSITY THERAPEUTIC ULTRASOUND (HITU)
TRANSDUCERS AND SYSTEMS
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62555 has been prepared by IEC technical committee
87: Ultrasonics
The text of this standard is based on the following documents:
FDIS Report on voting
87/538/FDIS 87/543/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

NOTE The following print types are used:
• Requirements: roman type
• Notes: in small roman type
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SIST EN 62555:2014
– 6 – 62555 © IEC:2013
• Words in bold in the text are defined in Clause 3.

• The numbers in square brackets refer to references given in the Bibliography which follows Annex G.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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SIST EN 62555:2014
62555 © IEC:2013 – 7 –
INTRODUCTION

In ultrasound fields at megahertz frequencies, output power is typically determined by

measuring the force on a target using a radiation force balance [1],[2],[3]. However, the

relationship between the radiation force and the output power is affected by the focusing or

other geometrical aspects of the field, by the type and shape of the target, by the distance of

the target from the transducer, by absorption (including ‘shock-loss’) in the water path, and by

acoustic streaming currents. Whilst many of these effects are small for typical diagnostic or

physiotherapy ultrasound fields, they cannot generally be ignored for HITU fields (particularly

for those often referred to as high intensity focused ultrasound HIFU) [4]. Furthermore, in

HITU, the quantity of interest is the power incident on the patient rather than the output power

at the transducer face. Since it is common to have a water stand-off between the transducer

and the patient, attenuation and shock-loss in the water path may be significant and will vary

depending upon the chosen distance.

The purpose of this International Standard is to establish standard methods of measurement

of ultrasonic power of HITU devices in liquids in the lower megahertz frequency range based

on the measurement of the radiation force using a gravimetric balance, and calorimetry

(based on the measurement of thermal expansion). This standard identifies the sources of

errors and describes a systematic step-by-step procedure to assess overall measurement

uncertainty as well as the precautions that should be undertaken and uncertainties that should

be taken into account while performing power measurements. Practical guidance is given for

the determination of acoustic power from the very wide range of transducer geometries used

for HITU. Unlike radiation force approaches in IEC 61161 that deal with “time average power,”

other power measurement methods are described in this document.

The structure and content of parts of this International Standard are largely based on

IEC 61161:2013 but there are differences that are summarised below. In this standard the

prime measurand is considered to be the incident power, and not the output power. Output

power is always the quantity of interest in IEC 61161, which specifies that measurements are

made with the target placed close to the transducer. However, this may not always be

possible for strongly convergent transducers and there are cases where it is more relevant to

measure the incident power which reaches a specified surface at some substantial distance

from the transducer (this surface may represent the skin surface of the patient, for instance).

This extra distance may result in significant nonlinear loss in the water path even at low

megahertz frequencies. Consequently, in this International Standard the prime measurand is

considered to be the incident power, and not the output power. The incident power may of

course be the basis for determining the output power using an appropriate model with its own

uncertainties.
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SIST EN 62555:2014
– 8 – 62555 © IEC:2013
ULTRASONICS – POWER MEASUREMENT –
HIGH INTENSITY THERAPEUTIC ULTRASOUND (HITU)
TRANSDUCERS AND SYSTEMS
1 Scope
This International Standard

• establishes general principles relevant to HITU fields for the use of radiation force

balances in which an obstacle (target) intercepts the sound field to be measured;

• specifies a calorimetric method of determining the total emitted acoustic power of

ultrasonic transducers based on the measurement of thermal expansion of a fluid-filled

target;

• specifies requirements related to the statement of electrical power characteristics of

ultrasonic transducers;

• provides guidance related to the avoidance of acoustic cavitation during measurement;

• provides guidance related to the measurement of HITU transducers of different

construction and geometry, including collimated, diverging and convergent transducers,

and multi-element transducers;
• provides guidance on the choice of the most appropriate measurement method;
• provides information on assessment of overall measurement uncertainties.

This International Standard is applicable to the measurement of ultrasonic power generated

by HITU equipment up to 500 W in the frequency range from 0,5 MHz to 5 MHz. HITU
equipment may generate convergent, collimated or divergent fields.

For frequencies less than 500 kHz, no validations exist and the user should assess the

uncertainties of the power measurement and measurement system at the frequencies of

operation.
This International Standard does not apply to:

• ultrasound equipment used for physiotherapy, for lithotripsy for general pain relief.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61161:2013, Ultrasonics – Power measurement – Radiation force balances and
performance requirements
IEC/TR 62781, Ultrasonics – Conditioning of water for ultrasonic measurements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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SIST EN 62555:2014
62555 © IEC:2013 – 9 –
3.1
acoustical efficiency

ratio of the acoustic output power from an ultrasonic transducer to the transducer

electrical power
Note 1 to entry: Acoustical efficiency is unitless.
3.2
acoustic streaming
bulk fluid motion initiated by a sound field
[SOURCE: IEC 61161:2013, 3.1]
3.3
buoyancy sensitivity

ratio of the increase in the buoyancy force on an expansion target to the amount of absorbed

energy in the absence of thermal losses
Note 1 to entry: This ratio may be temperature dependent.

Note 2 to entry: The buoyancy sensitivity for a fluid filled expansion target immersed in water is most

conveniently and most accurately determined by calibration using electrical heating (see 7.2.9). It can also be

calculated from the product of the expansion ratio, the density of the water and the acceleration due to gravity

but, in practice, this leads to higher uncertainties.

Note 3 to entry: Since most sensitive balances display weight in grams or millig

...

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