SIST EN IEC 62631-3-2:2024

SLOVENSKI STANDARD
01-februar-2024
Dielektrične in uporovne lastnosti trdnih izolacijskih materialov - 3-2. del:
Ugotavljanje uporovnih lastnosti (metode z enosmernim tokom) - Površinska
upornost in površinska specifična upornost (IEC 62631-3-2:2023)
Dielectric and resistive properties of solid insulating materials - Part 3-2: Determination of
resistive properties (DC methods) - Surface resistance and surface resistivity (IEC 62631
-3-2:2023)
Dielektrische und resistive Eigenschaften fester Isolierstoffe - Teil 3-2: Bestimmung
resistiver Eigenschaften (Gleichspannungsverfahren) - Oberflächenwiderstand und
spezifischer Oberflächenwiderstand (IEC 62631-3-2:2023)
Propriétés diélectriques et résistives des matériaux isolants solides - Partie 3-2:
Détermination des propriétés résistives (méthodes en courant continu) - Résistance
superficielle et résistivité superficielle (IEC 62631-3-2:2023)
Ta slovenski standard je istoveten z: EN IEC 62631-3-2:2023
ICS:
17.220.99 Drugi standardi v zvezi z Other standards related to
elektriko in magnetizmom electricity and magnetism
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62631-3-2

NORME EUROPÉENNE
EUROPÄISCHE NORM December 2023
ICS 17.220.99; 29.035.01 Supersedes EN 62631-3-2:2016
English Version
Dielectric and resistive properties of solid insulating materials -
Part 3-2: Determination of resistive properties (DC methods) -
Surface resistance and surface resistivity
(IEC 62631-3-2:2023)
Propriétés diélectriques et résistives des matériaux isolants Dielektrische und resistive Eigenschaften fester Isolierstoffe
solides - Partie 3-2: Détermination des propriétés résistives - Teil 3-2: Bestimmung resistiver Eigenschaften
(méthodes en courant continu) - Résistance superficielle et (Gleichspannungsverfahren) - Oberflächenwiderstand und
résistivité superficielle spezifischer Oberflächenwiderstand
(IEC 62631-3-2:2023) (IEC 62631-3-2:2023)
This European Standard was approved by CENELEC on 2023-11-20. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62631-3-2:2023 E

European foreword
The text of document 112/612/FDIS, future edition 2 of IEC 62631-3-2, prepared by IEC/TC 112
"Evaluation and qualification of electrical insulating materials and systems" was submitted to the IEC-
CENELEC parallel vote and approved by CENELEC as EN IEC 62631-3-2:2023.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-08-20
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-11-20
document have to be withdrawn
This document supersedes EN 62631-3-2:2016 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 62631-3-2:2023 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 standard indicated:
IEC 60893-2 NOTE Approved as EN 60893-2
IEC 61212-2 NOTE Approved as EN 61212-2
IEC 62011-2 NOTE Approved as EN 62011-2
ISO 10350 (series) NOTE Approved as EN ISO 10350 (series)
ISO 10350-1 NOTE Approved as EN ISO 10350-1
ISO 10350-2 NOTE Approved as EN ISO 10350-2
ISO 14526 (series) NOTE Approved as EN ISO 14526 (series)
ISO 14527 (series) NOTE Approved as EN ISO 14527 (series)
ISO 14528 (series) NOTE Approved as EN ISO 14528 (series)
ISO 14529 (series) NOTE Approved as EN ISO 14529 (series)
ISO 14530 (series) NOTE Approved as EN ISO 14530 (series)
ISO 15252 (series) NOTE Approved as EN ISO 15252 (series)
ISO 15512 NOTE Approved as EN ISO 15512
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60212 - Standard conditions for use prior to and EN 60212 -
during the testing of solid electrical
insulating materials
IEC 62631-3-1 - Dielectric and resistive properties of solid EN IEC 62631-3-1 -
insulating materials - Part 3-1:
Determination of resistive properties (DC
methods) - Volume resistance and volume
resistivity - General method
IEC 62631-3-3 - Dielectric and resistive properties of solid EN 62631-3-3 -
insulating materials - Part 3-3:
Determination of resistive properties (DC
methods) - Insulation resistance

IEC 62631-3-2 ®
Edition 2.0 2023-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Dielectric and resistive properties of solid insulating materials –
Part 3-2: Determination of resistive properties (DC methods) – Surface
resistance and surface resistivity
Propriétés diélectriques et résistives des matériaux isolants solides –
Partie 3-2: Détermination des propriétés résistives (méthodes en courant
continu) – Résistance superficielle et résistivité superficielle
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.99, 29.035.01 ISBN 978-2-8322-7549-8
– 2 – IEC 62631-3-2:2023 © IEC 2023
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Significance . 8
5 Method of test . 8
5.1 General . 8
5.2 Voltage . 9
5.3 Equipment . 9
5.3.1 General . 9
5.3.2 Accuracy . 9
5.3.3 Voltage source . 10
5.3.4 Electrode arrangements . 10
5.4 Test circuit . 14
5.5 Calibration . 15
5.6 Test specimen . 15
5.6.1 Recommended dimensions of test specimen and electrode
arrangements . 15
5.6.2 Manufacturing of test specimen . 15
5.6.3 Number of test specimens . 16
5.6.4 Application of conductive means . 16
5.6.5 Conditioning and pre-treatment of test specimen . 16
5.7 Test procedure . 17
6 Calculation of surface resistivity . 17
6.1 For electrode arrangements A, B, D and E . 17
6.2 For electrode arrangement C . 17
7 Test report . 18
8 Repeatability and reproducibility . 18
Annex A (informative) Specimen dimensions and electrode arrangements . 19
Annex B (informative) Comparative verification study on surface resistivities using
different electrode arrangements (type C and type E) . 20
B.1 General . 20
B.2 Inter-laboratory trial conditions . 20
B.2.1 General . 20
B.2.2 Test specimens . 20
B.2.3 Electrode types, conductive materials and test voltage . 20
B.2.4 Test conditions . 21
B.3 Summary of the test results . 21
B.4 Inter-laboratory trial outcomes and suggestions for IEC 62631-3-2 . 22
B.5 Detailed inter-laboratory results . 22
B.5.1 General . 22
B.5.2 Laboratories results by different groups of electrode types and
conductive materials for the different test specimens . 23
B.5.3 Laboratory 2 results comparing different electrode types and conductive
materials . 29
B.5.4 Laboratory 3 results – Electrode type C with and without use of
conductive silver paint . 31

IEC 62631-3-2:2023 © IEC 2023 – 3 –
Bibliography . 33

Figure 1 – Electrode arrangement A (example) . 11
Figure 2 – Electrode arrangement B (example) . 12
Figure 3 – Electrode arrangement C (example) . 13
Figure 4 – Connection diagram of measurement with two- and three-terminal electrode
arrangements. 15
Figure B.1 – Surface resistivity equations for the used electrodes . 21

Table 1 – Typical electrode dimensions for electrode arrangement C . 13
Table A.1 – Recommended test specimen dimensions and electrode arrangements for

specific products . 19
Table B.1 – Test specimens characteristics . 20
Table B.2 – Test conditions per specific participant . 21
Table B.3 – Summary of the test results . 22
Table B.4 – Polybutylene terephthalate (PBT) test specimen results – Electrode type C
with conductive rubber . 23
Table B.5 – Polyamide 66 (PA66) test specimen results – Electrode type C with
conductive rubber . 24
Table B.6 – Polybutylene terephthalate (PBT) test specimen results – Electrode type C
with conductive silver paint . 25
Table B.7 – Polyamide 66 (PA66) test specimen results – Electrode type C with
conductive silver paint . 26
Table B.8 – Polybutylene terephthalate (PBT results) test specimen results – Electrode
type E with conductive silver paint . 27
Table B.9 – Polyamide 66 (PA66) test specimen results – Electrode type E with
conductive silver paint . 28
Table B.10 – Laboratory 2 results – Polybutylene terephthalate (PBT) – Different
electrodes and conductive materials . 29
Table B.11 – Laboratory 2 results – Polyamide 66 (PA66) – Different electrodes and
conductive materials . 30
Table B.12 – Laboratory 3 results – Polybutylene terephthalate (PBT) – Electrode type
C with and without conductive silver paint . 31
Table B.13 – Laboratory 3 results – Polyamide 66 (PA66) – Electrode type C with and
without conductive silver paint . 32

– 4 – IEC 62631-3-2:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –

Part 3-2: Determination of resistive properties (DC methods) –
Surface resistance and surface resistivity

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
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC 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, IEC 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 https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 62631-3-2 has been prepared by IEC technical committee 112: Evaluation and qualification
of electrical insulating materials and systems. It is an International Standard.
This second edition cancels and replaces the first edition published in 2015. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) descriptions of the electrode arrangements have been clarified;
b) new descriptions of the conductive means have been added;

IEC 62631-3-2:2023 © IEC 2023 – 5 –
c) a new informative Annex B summarizing the results of the comparative verification study on
surface resistivities using different electrode arrangements has been added.
The text of this International Standard is based on the following documents:
Draft Report on voting
112/612/FDIS 112/619/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 62631 series, published under the general title Dielectric and
resistive properties of solid insulating materials, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC 62631-3-2:2023 © IEC 2023
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –

Part 3-2: Determination of resistive properties (DC methods) –
Surface resistance and surface resistivity

1 Scope
This part of IEC 62631 describes methods of test for the determination of surface resistance
and surface resistivity of electrical insulation materials by applying DC voltage.
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.
IEC 60212, Standard conditions for use prior to and during the testing of solid electrical
insulating materials
IEC 62631-3-1, Dielectric and resistive properties of solid insulating materials – Part 3-1:
Determination of resistive properties (DC methods) – Volume resistance and volume resistivity
– General method
IEC 62631-3-3, Dielectric and resistive properties of solid insulating materials – Part 3-3:
Determination of resistive properties (DC methods) – Insulation resistance
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:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
electrode arrangement
electrical conductive bodies on the surface of a test specimen
Note 1 to entry: The arrangement of electrodes should include procedures to ascertain sufficient contact to the
surface (e.g. by means of conducting paint) or the use of adequate mechanical system applying the necessary contact
force to the test specimen's surface or both.

IEC 62631-3-2:2023 © IEC 2023 – 7 –
3.1.1
annular electrode
central circular planar electrode with a surrounding ring electrode separated by a gap
SEE: Figure 3.
Note 1 to entry: Guard electrode systems as described in IEC 62321-3-1 are of similar shape. In the case of surface
resistance, the ring electrode does not have the function of a guard; guard functionality, however, is provided by the
opposite electrode.
3.1.2
line electrode
electrode arrangement provided by two parallel lines, separated by a gap, applied to the test
specimen's surface using a conductive material
SEE: Figure 2.
3.1.3
spring loaded electrode
line electrode system using two parallel lines of conducting spring tongues with sharp edges,
separated by a gap
SEE: Figure 1.
3.2
measured resistance
ratio of a DC voltage applied to an electrode arrangement in contact with a test specimen to the
current between them measured with sufficient precision
Note 1 to entry: A three-terminal electrode arrangement can be used to exclude undesired volume currents from
the determination of the measured resistance.
Note 2 to entry: A Wheatstone bridge can also be used to compare the measured resistance with a standard
resistor. However, Wheatstone bridges are not commonly used anymore.
Note 3 to entry: According to IEC 60050-121: Electromagnetism, "conductivity" (IEV 121-12-03) is defined as "the
scalar or tensor quantity, the product of which by the electric field strength in a medium is equal to the electric current
density" and "resistivity" (IEV 121-12-04) as "the inverse of the conductivity when this inverse exists". Measured in
this way, the surface resistivity integrates different electrical conduction pathways at the surface of the material or
in its nearby volume, with the possible presence of heterogeneities; it includes the effect of possible polarization
phenomena at the electrodes. Therefore, it is considered as an averaged value.
3.3
surface resistance
R
S
measured resistance between any electrode arrangement defined in IEC 62361-3-2
Note 1 to entry: Depending on the electrode arrangement used, it is designated as R , R , R , R or R with
SA SB SC SD SE
surface resistance, R expressed in Ω.
S
Note 2 to entry: An indeterminable part of the resistance inside the material is also included in surface resistance
during the measurement of this resistance.
3.4
R
SC
surface resistance between annular electrodes
measured resistance between the inner circular area of an annular electrode system and the
outer circular ring electrode
3.5
R
SD
surface resistance between line electrodes
measured resistance between line electrodes

– 8 – IEC 62631-3-2:2023 © IEC 2023
3.6
R
SE
surface resistance between line electrodes for small plates
measured resistance between line electrodes for small plates
3.7
R
SB
surface resistance between small line electrodes
measured resistance between small line electrodes
3.8
R
SA
surface resistance between spring load electrodes
measured resistance between spring loaded electrodes
3.9
surface resistivity
σ/square
surface resistance reduced to a square
Note 1 to entry: The numerical value of surface resistivity is independent of the size of the square.
Note 2 to entry: Surface resistance R , R , R , R and R referred to a square, are expressed as σ , σ , σ ,
SA SB SC SD SE A B C
σ and σ respectively.
D E
Note 3 to entry: Surface resistivity is often expressed by the non-standardized unit Ω per square, to show that the
electrode dimension has been taken into account by calculating the specific value.
Note 4 to entry: The surface resistivity is often used to compare one kind of surface characteristic of a sample
material with those of other materials. It can be compared for materials only if identical standardized dimensions of
the electrodes are used. Recommended dimensions are given in 5.3.
4 Significance
Insulating materials are used in general to electrically isolate components of an electrical
system from each other and from the earth. Solid insulating materials can also provide
mechanical support. For this purpose, it is generally desirable to have the insulation resistance
as high as possible, consistent with acceptable mechanical, chemical and heat resistance
properties.
Surface resistance is, as volume resistance, a part of the insulating resistance.
Insulating resistance shall be determined according to IEC 62631-3-3 and volume resistance
according to IEC 62631-3-1.
Surface resistance supplies information on the electrical resistances of the surface of materials
and products. Surface resistance, however, for its major part is not a materials' property.
Surface resistance depends mainly on processing parameters, environmental conditions,
surface ageing phenomena and pollution, etc.
NOTE Depending on the specific application, different electrode arrangements can be preferable.
5 Method of test
5.1 General
This general method describes common values for general measurements. If a method for a
specific type of material is described in this document, the specific method shall be used.

IEC 62631-3-2:2023 © IEC 2023 – 9 –
Different types of electrodes can be used, depending on the specific measurement or product
demands. For instance, on surfaces with a curved shape, a small line electrode can be
advantageous. Spring loaded electrodes provide measurements with low effort on products and
are optimal for materials which have to be conditioned before the test. If not already stipulated
by a product standard, the choice of the electrode arrangement shall be made considering the
typical application.
If test specimens are made from materials (e.g. soft rubber) whose dimensions will change
significantly as a result of the force applied by the electrodes on them, these electrodes are not
applicable and an alternative arrangement shall be used.
If no information about the application is available, small line electrodes (R ) are
SB
recommended.
5.2 Voltage
The measuring voltage should preferably be 10 V, 100 V, 500 V, 1 000 V, 10 000 V.
If not otherwise specified by the relevant product standard, a voltage of 100 V shall be used.
Technical committees shall specify the preferred test voltage when referring to this document.
NOTE 1 Partial discharge can lead to erroneous measurements when a specific inception voltage is exceeded. In
air, below 340 V, no partial discharges will occur.
−5
NOTE 2 The ripple of the voltage source is important. A typical value for 100 V is < 5 × 10 peak to peak.
5.3 Equipment
5.3.1 General
Care should be taken that the surface resistance is not negatively influenced by parasitic
resistances parallel to the electrode arrangement, such as the resistance of test supports or
cable isolation.
Ω, shielded cables and
To prevent measuring errors for measured resistances higher than 10
shielded measuring cabinets shall be used.
For the determination of surface resistance and surface resistivity, different electrode
arrangements can be used. The evaluation of surface resistivity is dependent on the selected
electrode arrangement.
NOTE Comparison between measurement results can be done only between measurements performed using the
same electrode arrangements and conductive means.
5.3.2 Accuracy
Any suitable equipment can be used. The measuring device shall be capable of determining the
unknown resistance with an overall accuracy of at least
• ±10 % for resistances less than 10 Ω;
10 14
• ±20 % for resistances between 10 Ω and 10 Ω; and
• ±50 % for resistances higher than 10 Ω.
NOTE The provided accuracies have been confirmed through the round robin test results reported in Annex B.

– 10 – IEC 62631-3-2:2023 © IEC 2023
5.3.3 Voltage source
A source of steady direct voltage is required. This can be provided either by batteries or by
rectified and stabilized power supply. The degree of stability required is such that the change
in current due to any change in voltage is negligible compared with the current to be measured.
5.3.4 Electrode arrangements
5.3.4.1 General
Electrode arrangements consist of the combination of electrodes and conductive means. The
conductive means shall be applied to the test specimen before performing the measurements.
Electrodes are then placed in contact with the conductive means applied on the test specimen
in order to perform measurements.
NOTE Annex B contains the results of the comparative verification study on surface resistivities using different
electrode arrangements.
5.3.4.2 Electrode arrangement A – Spring loaded electrodes
The electrode arrangement A shall consist of two flexible metal knife-edges with a length of
100 mm and a gap distance of 10 mm as shown in Figure 1.
No guard electrode is used. The metal knife-edges shall consist of individual spring tongues
arranged next to each other about 0,3 mm apart and each with a length not exceeding 5,0 mm
and 0,3 mm thick. The contact force shall be high enough so that all tongues or segments rest
against the surface of the test specimen, but without damaging the surface.
A piece of metal exerting the contact force shall be applied with high-grade insulation where in
contact with the specimen.
IEC 62631-3-2:2023 © IEC 2023 – 11 –
Dimensions in millimetres
Key
1 guide bar (detachable)
2 metal knife-edges
3 specimen
Figure 1 – Electrode arrangement A (example)
5.3.4.3 Electrode arrangement B – Small line electrodes
Electrode arrangement B shall consist of a two-terminal collector with conductive blades being
in contact with the conductive means on the test specimen, as shown in Figure 2. No guard
electrode is used.
For the purpose of electrode arrangement B, conductive means shall be applied as two 1,5 mm
wide lines with a length of 25,0 mm and a gap distance of 2,0 mm. Lines shall be applied before
conditioning.
– 12 – IEC 62631-3-2:2023 © IEC 2023
Types of conductive means and the related applications are described in 5.6.4.

Figure 2 – Electrode arrangement B (example)
5.3.4.4 Electrode arrangement C – Annular electrodes
Electrode arrangement C is a three-terminal electrode system, as shown in Figure 3. On one
side of the test specimen, annular electrodes are applied. The opposite surface of the test
specimen shall be covered by a guard electrode, not smaller than the area covered by the
corresponding electrodes.
IEC 62631-3-2:2023 © IEC 2023 – 13 –

Key
1 specimen
2 electrode 1
3 measuring area
4 electrode 2
5 electrode 3 (guard electrode)
a thickness of the test specimen
d electrode 1 diameter
d electrode 2 internal diameter
d electrode 2 external diameter
d median diameter of measuring area
m
Figure 3 – Electrode arrangement C (example)
Any electrode dimensions can be used, unless otherwise specified by the relevant product
standard. Typical electrode dimensions are given in Table 1. For comparison tests, electrode
arrangement C1 is recommended.
Table 1 – Typical electrode dimensions for electrode arrangement C
d d d
1 2 3
Electrode arrangement
mm mm mm
C1 50 60 80
C2 76 88 100
C3 25 38 50
With electrode arrangement C, the surface resistance between electrode 1 and electrode 2 shall
be measured. Electrode 3 shall be earthed.
Either of the conductive means described in 5.6.4 shall be placed or painted on the surface
areas where electrode 1, electrode 2 and electrode 3 are placed. The conductive means shall
not be applied on the surface between electrode 1 and electrode 2.
NOTE In the case of materials with limited conductivity and also occasionally films having a thickness of ≤ 10 µm,
the input resistance of the ammeter is significantly smaller than the volume resistance of the test specimen.

– 14 – IEC 62631-3-2:2023 © IEC 2023
5.3.4.5 Electrode arrangement D – Line electrodes
Electrode arrangement D shall consist of a two-terminal collector electrode arrangement with
conductive blades being in contact with the conductive means on the test specimen, as shown
in Figure 2. No guard electrode is used.
For the purpose of electrode arrangement D, the conductive means shall be applied as two
parallel 1,5 mm wide lines with a length of (100,0 ± 1,0) mm and a gap distance of
(10,0 ± 0,5) mm. They can be applied before the treatment.
The types of conductive means and the related applications are described in 5.6.4.
5.3.4.6 Electrode arrangement E – Line electrodes for small plates
Electrode arrangement E consists of a three-terminal collector electrode as shown in Figure 4,
item B).
For the purpose of electrode arrangement E the conductive means shall be applied as two
parallel 1,0 mm to 2,0 mm wide lines with a length of (50,0 ± 1,0) mm and a gap distance of
(5,0 ± 0,5) mm that can be applied before conditioning of the test specimen.
The opposite surface of the test specimen shall be covered by a guard electrode not smaller
than the area covered by the corresponding electrodes.
Types of conductive means and the related applications are described in 5.6.4.
NOTE Examples of combination of electrode types and dimensions of test specimens are provided in Annex A.
5.4 Test circuit
Depending on the electrode arrangement selected, two- or three-terminal measurements shall
be carried out (see Figure 4).
For annular electrodes (electrode arrangement C) and line electrode arrangement E,
a three-terminal test circuit is necessary as a grounded protective electrode is mandatory.
For any other line electrode arrangement (A, B and D), a two-terminal test circuit shall be used.

IEC 62631-3-2:2023 © IEC 2023 – 15 –

Key
a voltage source
b voltmeter
c ammeter
d electrode 1
e electrode 2 (shielded electrode)
f electrode 3 (protective electrode)
g specimen
Figure 4 – Connection diagram of measurement with two- and
three-terminal electrode arrangements
5.5 Calibration
The equipment shall be calibrated in the magnitude of the surface resistance measured.
NOTE Calibration resistors in a range up to 100 TΩ are commercially available.
5.6 Test specimen
5.6.1 Recommended dimensions of test specimen and electrode arrangements
The specimen’s dimensions shall be sufficient to apply the selected electrode arrangement.
Recommendations for products are given in Annex A.
5.6.2 Manufacturing of test specimen
The production and shape of the test specimen shall be determined by the relevant standards
for the material. During removal and production of the specimen, the condition of the material
shall not be changed and the specimen removed shall not be damaged.
If the surface of the test specimen is machined at the contact areas of the electrodes, the type
of machining shall be specified in the test report. The test specimen shall have a geometrically
simple shape (plate with parallel measuring areas, cylinder, etc.).
NOTE Machining of the test specimen can be performed on the specimen when it is representative of the application
target for the materials.
– 16 – IEC 62631-3-2:2023 © IEC 2023
Specimen from products shall be prepared with the product thickness, if possible.
5.6.3 Number of test specimens
The number of test specimens to be tested shall be determined by the relevant product
standards. If no such data is available, at least three specimens shall be tested.
5.6.4 Application of conductive means
5.6.4.1 General
When using adhesive conductive means (electrode arrangements B, C, D and E), ensure that
a proper contact is provided over the whole area covered. The conductive means used shall,
after an appropriate time of conditioning, not influence the measured values for surface
resistance.
NOTE 1 Conductive silver paint and suspensions of graphite have been found appropriate.
NOTE 2 Annex B contains the results of the comparative verification study on surface resistivities using different
electrode arrangements and conductive means.
5.6.4.2 Conductive silver paint
Certain types of commercially available, high-conductivity silver paints, either air-drying or low-
temperature-baking varieties, are sufficiently porous to permit diffusion of moisture through
them and thereby allow the test specimens to be conditioned after application of the conductive
means. This is a particularly useful feature in studying resistance-humidity effect as well as
changes with temperature. However, before conductive paint is used as a conductive means, it
should be established that the paint solvent does not affect the electrical properties of the
specimen. Reasonably smooth edges for use with guard electrodes can be obtained with a
fine-bristle brush. However, for use with circular electrodes, sharper edges can be obtained by
the use of a compass for drawing the outline circles of the electrodes and filling in the enclosed
areas by brush. Clamp-on masks can be used if the conductive paint is sprayed on.
5.6.4.3 Colloidal graphite
Colloidal graphite dispersed in water or other suitable medium, can be used under the same
conditions as given for conductive silver paint.
5.6.4.4 Conducting rubber
Conducting rubber can be used as conductive means. It has the advantage that it can be applied
and removed from the specimen quickly and easily. Since the conductive means are applied
only during the time of measurement, they do not interfere with the conditioning of the specimen.
The resistance of the rubber electrode shall be less than 1 000 Ω.
The conducting rubber material shall be soft enough to ensure that effective contact to the
specimen is obtained when a reasonable pressure, for example 2 kPa (0,2 N/cm ), is applied.
Shore A hardness according to ISO 48-4 in the range of 65 to 85 has been found suitable.
NOTE The results of resistivity measurements obtained with the application of electrodes made of conducting rubber
are always higher (few tens to few hundreds per
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