SIST EN ISO 32543-5:2026

Non-destructive testing - Characteristics of focal spots in industrial X-ray systems - Part 3: Measurement of the effective focal spot size of mini and micro focus X-ray tubes (ISO 32543-3:2026)

This document specifies a method for the measurement of focal spot sizes within the range of 5 µm to 300 µm of X-ray systems up to and including 225 kV tube voltage. This determination is based on the evaluation of an image with a dedicated focal spot that has been radiographically recorded using an edge and evaluated with a digital method.
The imaging quality and the resolution of X-ray images depend highly on the characteristics of the effective focal spot, in particular its size and the two-dimensional intensity distribution as seen from the detector plane.
For the characterization of commercial X-ray tube types (i.e. for advertising or trade), the nominal values of Annex A are preferred.
NOTE            The same procedure can be used at higher kilovoltages by agreement but the accuracy of the measurement can be poorer.

Zerstörungsfreie Prüfung - Charakterisierung von Brennflecken in Industrie-Röntgenanlagen - Teil 3: Messung der effektiven Brennfleckgröße von Mini- und Mikrofokus-Röntgenröhren (ISO 32543-3:2026)

Dieses Dokument legt ein Verfahren für die Messung von Brennfleckengrößen im Bereich von 5 µm bis 300 µm von Röntgensystemen bis einschließlich 225 kV Röhrenspannung fest. Diese Bestimmung basiert auf der Auswertung eines Bildes mit einem bestimmten Brennfleck, das mit einer Kante radiographisch aufgenommen und mit einem digitalen Verfahren ausgewertet wurde.
Die Bildgüte und die Auflösung von Röntgenbildern hängen in hohem Maße von den Eigenschaften des effektiven Brennflecks ab, insbesondere von seiner Größe und zweidimensionalen Intensitätsverteilung, wie von der Detektorebene aus gesehen.
Für die Charakterisierung handelsüblicher Röntgenröhrentypen (z. B. für Werbung oder Handel) werden die Nennwerte von Anhang A bevorzugt.
ANMERKUNG   Dasselbe Verfahren kann nach Absprache auch bei höheren Kilospannungen angewendet werden, aber die Messgenauigkeit kann schlechter sein.

Essais non destructifs - Caractéristiques des foyers émissifs des tubes radiogènes industriels - Partie 3: Mesurage de la taille des foyers émissifs effectifs de tubes radiogènes à minifoyer ou à microfoyer (ISO 32543-3:2026)

Le présent document spécifie une méthode de détermination des tailles de foyer émissif, dans la gamme de 5 µm à 300 µm, des tubes radiogènes de tension inférieure ou égale à 225 kV. Cette détermination repose sur l’évaluation, au moyen d’une méthode numérique, d’une image d’un foyer émissif dédié qui a été enregistrée radiographiquement à l’aide d’une technique par effet de bord.
La qualité d’image et la résolution des images radiographiques dépendent étroitement des caractéristiques du foyer émissif effectif, en particulier de sa taille et de la répartition bidimensionnelle de l’intensité observée depuis le plan du détecteur.
Pour la caractérisation des tubes radiogènes de type commercial (c’est-à-dire destinés à la publicité ou au commerce), les valeurs nominales indiquées à l’Annexe A sont privilégiées.
NOTE            Il est possible de convenir de l’utilisation du même mode opératoire à des valeurs de tension (en kV) plus élevées; cependant, l’exactitude du mesurage peut s’en trouver altérée.

Neporušitvene preiskave - Značilnosti goriščne površine v industrijskih rentgenskih sistemih - 3. del: Meritve efektivne velikosti goriščne površine za mini in mikro goriščne rentgenske aparate (ISO 32543-3:2026)

Ta dokument določa metodo za merjenje velikosti žariščne točke v razponu od 5 µm do 300 µm za rentgenske sisteme do vključno 225 kV napetosti cevi. Ta določitev temelji na oceni slike z namensko žariščno točko, ki je bila radiografsko posneta z uporabo roba in ocenjena z digitalno metodo.
Kakovost slike in ločljivost rentgenskih slik sta močno odvisni od značilnosti učinkovite žariščne točke, zlasti njene velikosti in dvodimenzionalne porazdelitve intenzitete, kot jo vidi detektorska ravnina.
Za karakterizacijo komercialnih tipov rentgenskih cevi (tj. za oglaševanje ali trgovino) so prednostne nominalne vrednosti iz Priloge A.
OPOMBA Postopek se lahko uporablja tudi pri višjih napetostih v kilovoltih po dogovoru, vendar je lahko natančnost merjenja slabša.

General Information

• Status: Published
• Publication Date: 09-Apr-2026
• ICS: 19.100 - Non-destructive testing
• Technical Committee: PKG - Testing of metallic materials
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 28-Jan-2026
• Due Date: 04-Apr-2026
• Completion Date: 10-Apr-2026
• Ref Project: EN ISO 32543-3:2026 - Non-destructive testing - Characteristics of focal spots in industrial X-ray systems - Part 3: Measurement of the effective focal spot size of mini and micro focus X-ray tubes (ISO 32543-3:2026)

Relations

• Referred By: SIST EN ISO 17636-1:2013 - Non-destructive testing of welds - Radiographic testing - Part 1: X- and gamma-ray techniques with film (ISO 17636-1:2013)
• Effective Date: 28-Jan-2026
• Referred By: SIST EN ISO 17636-1:2023 - Non-destructive testing of welds - Radiographic testing - Part 1: X- and gamma-ray techniques with film (ISO 17636-1:2022)
• Effective Date: 28-Jan-2026
• Referred By: SIST EN ISO 17636-2:2023 - Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray techniques with digital detectors (ISO 17636-2:2022)
• Effective Date: 28-Jan-2026
• Referred By: SIST EN ISO 16371-2:2018 - Non-destructive testing - Industrial computed radiography with storage phosphor imaging plates - Part 2: General principles for testing of metallic materials using X-rays and gamma rays (ISO 16371-2:2017, Corrected version 2018-05)
• Effective Date: 28-Jan-2026
• Referred By: SIST EN ISO 5579:2014 - Non-destructive testing - Radiographic testing of metallic materials using film and X- or gamma rays - Basic rules (ISO 5579:2013)
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 12681-2:2018 - Founding - Radiographic testing - Part 2: Techniques with digital detectors
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 12681-1:2018 - Founding - Radiographic testing - Part 1: Film techniques
• Effective Date: 28-Jan-2026
• Revises: SIST EN 12543-5:2000 - Non-destructive testing - Characteristics of focal spots in industrial X-ray systems for use in non-destructive testing - Part 5: Measurement of the effective focal spot size of mini and micro focus X-ray tubes
• Effective Date: 13-Dec-2023

Overview

FprEN ISO 32543-3 defines a digital, edge-based method to measure the effective focal spot size of mini and micro‑focus X‑ray tubes used in non‑destructive testing (NDT). The standard covers measurements in the range 5 µm to 300 µm for X‑ray systems up to and including 225 kV. Accurate focal spot characterization is essential because the focal spot size and its two‑dimensional intensity distribution directly affect image sharpness, spatial resolution and defect detectability in radiographic NDT.

Key Topics

• Measurement scope: Effective focal spot size determination for mini/micro‑focus tubes (5–300 µm) and guidance for commercial tube classification using preferred values in Annex A.
• Method principle: Indirect measurement by imaging a sharp edge (or wire/sphere test object) with high geometric magnification; digital profile evaluation yields the effective size and two‑directional dimensions.
• Permitted detectors and media:
  • Film systems (class C2 per EN ISO 11699‑1) without screens
  • Computed radiography (CR) imaging plates compliant with ISO 16371
  • Radioscopic devices and Digital Detector Arrays (DDA)
• Equipment and test object: High‑absorption wires or spheres (e.g., tungsten) mounted to minimize penetration and scattering; Unsharpness Gage per EN ISO 19232‑5 is recommended.
• Image quality requirements: Guidance on exposure, magnification, signal‑to‑noise (SNR) and contrast‑to‑noise (CNR) to ensure measurement precision. Examples in the standard include film background density targets and digital saturation thresholds.
• Practical constraints: Minimum distance between focal spot and test object (at least five times the wire/sphere diameter); avoid additional X‑ray prefiltering where possible.

Applications

• Routine NDT quality assurance: Verify focal spot performance during acceptance testing and maintenance of micro‑focus X‑ray tubes.
• Manufacturer tube characterization: Provide standardized, comparable focal spot values for marketing, specification sheets and class assignment (see Annex A preferred maxima).
• Image optimization: Use measured focal spot dimensions to select appropriate imaging geometry, detector pixel size and exposure settings to achieve required resolution for defect detection.

Related Standards

This document is part of a family of focal spot characterization standards for industrial radiography. Related parts and references include:

• EN 12543‑2 (pinhole camera method for larger spots)
• EN 12543‑4 (edge/penetrameter methods for field checks)
• EN 12543‑6 (line‑pair method for < 5 µm spots)
• EN ISO 11699‑1, EN ISO 19232‑5, ISO 16371 (normative references on film, image quality and CR)

Practical value: Implementing FprEN ISO 32543-3 helps laboratories and manufacturers quantify focal spot dimensions reproducibly, improving NDT image fidelity and enabling reliable comparisons across X‑ray tube types.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2026
Neporušitvene preiskave - Značilnosti goriščne površine v industrijskih
rentgenskih sistemih - 3. del: Meritve efektivne velikosti goriščne površine za mini
in mikro goriščne rentgenske aparate (ISO 32543-3:2026)
Non-destructive testing - Characteristics of focal spots in industrial X-ray systems - Part
3: Measurement of the effective focal spot size of mini and micro focus X-ray tubes (ISO
32543-3:2026)
Zerstörungsfreie Prüfung - Charakterisierung von Brennflecken in Industrie-
Röntgenanlagen - Teil 3: Messung der effektiven Brennfleckgröße von Mini- und
Mikrofokus-Röntgenröhren (ISO 32543-3:2026)
Essais non destructifs - Caractéristiques des foyers émissifs des tubes radiogènes
industriels - Partie 3: Mesurage de la taille des foyers émissifs effectifs de tubes
radiogènes à minifoyer ou à microfoyer (ISO 32543-3:2026)
Ta slovenski standard je istoveten z: EN ISO 32543-3:2026
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 32543-3
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2026
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN 12543-5:1999
English Version
Non-destructive testing - Characteristics of focal spots in
industrial X-ray systems - Part 3: Measurement of the
effective focal spot size of mini and micro focus X-ray
tubes (ISO 32543-3:2026)
Essais non destructifs - Caractéristiques des foyers Zerstörungsfreie Prüfung - Charakterisierung von
émissifs des tubes radiogènes industriels - Partie 3: Brennflecken in Industrie-Röntgenanlagen - Teil 3:
Mesurage de la taille des foyers émissifs effectifs de Messung der effektiven Brennfleckgröße von Mini- und
tubes radiogènes à minifoyer ou à microfoyer (ISO Mikrofokus-Röntgenröhren (ISO 32543-3:2026)
32543-3:2026)
This European Standard was approved by CEN on 25 December 2025.

CEN 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 CEN
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 CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 32543-3:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 32543-3:2026) has been prepared by Technical Committee ISO/TC 135 "Non-
destructive testing" in collaboration with Technical Committee CEN/TC 138 “Non-destructive testing”
the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by July 2026, and conflicting national standards shall be
withdrawn at the latest by July 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 12543-5:1999.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 32543-3:2026 has been approved by CEN as EN ISO 32543-3:2026 without any
modification.
International
Standard
ISO 32543-3
First edition
Non-destructive testing —
2026-01
Characteristics of focal spots in
industrial X-ray systems —
Part 3:
Measurement of the effective focal
spot size of mini and micro focus
X-ray tubes
Essais non destructifs — Caractéristiques des foyers émissifs des
tubes radiogènes industriels —
Partie 3: Mesurage de la taille des foyers émissifs effectifs de tubes
radiogènes à minifoyer ou à microfoyer
Reference number
ISO 32543-3:2026(en) © ISO 2026

ISO 32543-3:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 32543-3:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 3
5 Test method . 4
5.1 Principle and equipment .4
5.1.1 Detection equipment .4
5.1.2 Test object . .5
5.2 Selection of distances and exposure time .5
6 Measurement and determination of the focal spot size . 7
6.1 Measurement .7
6.2 Correction of the detector unsharpness .10
6.3 Classification and result of focal spot size evaluation .10
7 Test report .11
Annex A (Informative) Preferred values for the classification of X-ray tube micro- focal spot
sizes.12
Bibliography . 14

iii
ISO 32543-3:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by ISO Technical Committee TC 135, Non-destructive testing, Subcommittee
SC 5, Radiographic testing, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 138, Non-destructive testing, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 32543 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 32543-3:2026(en)
Introduction
To cover the large range of effective focal spot sizes, different methods are specified in ISO 32543 series.
In ISO 32543-1, the pin hole method permits the measurement of focal spot shape and focal spot
sizes ≥ 100 µm.
The edge measurement method of ISO 32543-2 is intended as a user method for measurement of effective
focal spot sizes of nano-, micro-, mini- and macro- (standard) focus tubes.
This document (ISO 32543-3) covers the measurement of the effective focal spot sizes between 5 µm and
300 µm of microfocus X-ray tubes.
Two further methods are in preparation as future parts in ISO 32543 series, concerning:
1)
— ISO 32543-4 line pair test objects for measuring the effective focal spot size of micro- and nanofocus
X-ray tubes with focal spot sizes ranging from 0,2 µm to 100 µm. This method is intended for use by
manufacturers and users;
2)
— ISO 32543-5 reconstruction of the spot shape from hole or disk test object measurements. The results
are equivalent to the pin hole method down to 0,2 µm, if no phase contrast is observed.
In the overlapping ranges, the different methods give similar values based on the edge response
measurement, which allow using the dedicated method also in a limited way outside the above specified
ranges.
1) Under preparation. Stage at the time of publication: ISO/AWI 32543-4.
2) Under preparation. Stage at the time of publication: ISO/AWI 32543-5.

v
International Standard ISO 32543-3:2026(en)
Non-destructive testing — Characteristics of focal spots in
industrial X-ray systems —
Part 3:
Measurement of the effective focal spot size of mini and micro
focus X-ray tubes
1 Scope
This document specifies a method for the measurement of focal spot sizes within the range of 5 µm to 300 µm
of X-ray systems up to and including 225 kV tube voltage. This determination is based on the evaluation of
an image with a dedicated focal spot that has been radiographically recorded using an edge and evaluated
with a digital method.
The imaging quality and the resolution of X-ray images depend highly on the characteristics of the effective
focal spot, in particular its size and the two-dimensional intensity distribution as seen from the detector
plane.
For the characterization of commercial X-ray tube types (i.e. for advertising or trade), the nominal values of
Annex A are preferred.
NOTE The same procedure can be used at higher kilovoltages by agreement but the accuracy of the measurement
can be poorer.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 11699-1, Non-destructive testing — Industrial radiographic film — Part 1: Classification of film systems for
industrial radiography
ISO 16371-1, Non-destructive testing — Industrial computed radiography with storage phosphor imaging plates
— Part 1: Classification of systems
ISO 19232-5, Non-destructive testing — Image quality of radiographs — Part 5: Determination of the image
unsharpness and basic spatial resolution value using duplex wire-type image quality indicators
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

ISO 32543-3:2026(en)
3.1
actual focal spot
X-ray emitting area of the anode as viewed from a position perpendicular to the anode surface
Note 1 to entry: The actual focal spot is also called thermal focal spot in other literature.
[SOURCE: ISO 32543-1:2024, 3.1]
3.2
effective focal spot
X-rays emitting area of the anode as viewed from the image plane of the detector
Note 1 to entry: The effective focal spot is also called optical focal spot in other literature.
[SOURCE: ISO 32543-1:2024, 3.2]
3.3
effective focal spot size
d
measured focal spot size
Note 1 to entry: For measurement and determination, see Clause 6.
[SOURCE: ISO 32543-1:2024, 3.3, modified — deleted the part “in accordance with this document” and added
Note 1 to entry, added symbol “d”.]
3.4
nominal focal spot size
SS
characteristic value for X-ray tubes having measured spot sizes within a defined range
Note 1 to entry: The nominal focal spot size is determined from Table A.1 based on the measured focal spot, d .
ERV50
[SOURCE: ISO 32543-1:2024, 3.4, modified — Note 1 to entry added.]
3.5
focal spot class
FS
number used to classify X-ray tubes based on the nominal focal spot size (3.4)
Note 1 to entry: The ranges of focal spot sizes are specified in Table A.1
[SOURCE: ISO 32543-1:2024, 3.5, modified — Note 1 to entry added.]
3.6
signal-to-noise ratio
SNR
ratio of mean grey value to the standard deviation of the grey values (noise) measured in a region of interest
Note 1 to entry: Grey values are numeric values of pixels, which are directly proportional to the detector exposure
dose and having a value of zero, if the detector was not exposed.
Note 2 to entry: After detector correction, a grey value of zero is obtained, if the detector is not exposed.
[SOURCE: ISO 32543-2:2026, 3.8]
3.7
contrast-to-noise ratio
CNR
ratio of the difference of the mean grey values between two image areas to the averaged standard deviation
of the grey value
[SOURCE: ISO 32543-2:2026, 3.9]

ISO 32543-3:2026(en)
3.8
anticipated focal spot size
d
ap
size of a focal spot as provided by a manufacturer, a specification or obtained by an older measurement
[SOURCE: ISO 32543-2:2026, 3.12]
3.9
interpolated basic spatial resolution value
detector
iSR
b
smallest geometrical detail, which can be resolved in a digital image at magnification
equal to one and corresponds to half of the measured interpolated detector unsharpness in a digital image
Note 1 to entry: The measurement of interpolated unsharpness is specified in ISO 19232-5 and ASTM E2002. See also
ASTM E1000 and ASTM E2736.
[SOURCE: ISO 32543-2:2025, 3.11]
4 Symbols and abbreviated terms
For the purposes of this document, the symbols and abbreviated terms given in Table 1 apply.
Table 1 — Symbols and abbreviated terms
Symbol or abbreviated Definition
term
CNR contrast-to-noise ratio
D projected diameter of the wire into the detector plane, oriented for the length measure-
L
ment
D projected diameter of the
...