EN ISO 17657-3:2007

• Abstract:

  ISO 17657-3:2005 specifies current sensing coils of the toroidal-coil type as a current sensor for welding current meters or a welding current measuring system used to monitor the welding current in resistance welding, and is applicable for both current types, i.e. alternating current of 50 Hz or 60 Hz and direct current.

• Status: Published
• Publication Date: 19-Jun-2007
• Withdrawal Date: 30-Dec-2007
• ICS: 25.160.10 - Welding processes
• Technical Committee: CEN/TC 121 - Welding
• Drafting Committee: CEN/TC 121 - Welding
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 20-Jun-2007
• Due Date: 26-May-2008
• Completion Date: 20-Jun-2007
• Ref Project: SIST EN ISO 17657-3:2007 - Resistance welding - Welding current measurement for resistance welding - Part 3: Current sensing coil (ISO 17657-3:2005)

• Refers: ISO 669:2000 - Resistance welding — Resistance welding equipment — Mechanical and electrical requirements
• Effective Date: 25-Aug-2026
• Refers: ISO 17657-4:2005 - Resistance welding — Welding current measurement for resistance welding — Part 4: Calibration system
• Effective Date: 25-Aug-2026
• Refers: EN ISO 9241-410:2008/A1:2012 - Ergonomics of human-system interaction - Part 410: Design criteria for physical input devices (ISO 9241-410:2008/AMD 1:2012)
• Effective Date: 28-Jan-2026

Overview

EN ISO 17657-3:2007 (ISO 17657-3:2005) specifies requirements for toroidal current sensing coils used as sensors in welding current measurement systems for resistance welding. The standard applies to both 50 Hz/60 Hz alternating current and direct current, and defines how coils are classified, specified, tested and marked for use with welding current meters and measuring systems.

Key topics and requirements

• Scope and environment
  • Designed for use in typical welding atmospheres (gas, fine dust, oil mist, spatters).
  • Operating conditions: ambient +5 °C to +40 °C, relative humidity up to 95 %, altitudes up to 1 000 m.
• Sensor type
  • Focus on toroidal (multi-wound) coils that encircle the conductor carrying welding current.
• Conversion coefficient (K)
  • Defined as output voltage per welding current (mV/kA). Standard rated values at 50 Hz: 150 mV/kA, 220 mV/kA, 1.5 V/kA.
  • Value is proportional to frequency; conversion between 60 Hz and 50 Hz is specified (60 Hz values divided by 1.2 to obtain 50 Hz equivalent).
• Accuracy classes
  • Highly accurate: ±0.5 % of full scale (laboratory)
  • Accurate: ±1.0 % of full scale (routine high-accuracy systems)
  • Ordinary: ±3.0 % of full scale (ordinary systems)
• Electrical and mechanical requirements
  • Coil output is proportional to the derivative of the current waveform - integrators/amplifiers are required to recover current magnitude.
  • Output load resistor recommended between 200 Ω and 1 kΩ; measurement instrumentation should use >500 kΩ input impedance for conversion checks.
  • Design measures to avoid sensitivity to external magnetic flux; low-inductance, protected leads and connectors.
• Tests and verification
  • Procedures for measuring the conversion coefficient, accuracy, mechanical strength, setting-position error, thermal behavior and contact integrity are specified.
• Product designation and marking
  • Requirements for indicating type (flexible/rigid), size (length or inner diameter), conversion coefficient, frequency and accuracy class.

Applications and users

• Practical uses:
  • Monitoring and controlling welding current in resistance spot welding, seam welding and other resistance welding processes.
  • Calibration, verification and quality assurance of welding systems.
• Primary users:
  • Sensor and welding equipment manufacturers, calibration laboratories, welding engineers, quality and process-control teams, procurement specialists specifying measurement hardware.

Related standards

• ISO 17657 series:
  • Part 1: Guidelines for measurement
  • Part 2: Welding current meter with current sensing coil
  • Part 4: Calibration system
  • Part 5: Verification of welding current measuring system
• Normative reference: ISO 669 (resistance welding equipment requirements)

Keywords: EN ISO 17657-3:2007, current sensing coil, toroidal coil, welding current measurement, resistance welding, conversion coefficient, accuracy class, welding current meter.

SLOVENSKI STANDARD
01-september-2007
Uporovno varjenje - Merjenje jakosti varilnega toka pri uporovnem varjenju - 3. del:
Merilna tuljava (ISO 17657-3:2005)
Resistance welding - Welding current measurement for resistance welding - Part 3:
Current sensing coil (ISO 17657-3:2005)
Widerstandsschweißen - Schweißstrommessung für das Widerstandsschweißen - Teil 3:
Strommessspule (ISO 17657-3:2005)
Soudage par résistance - Mesurage des courants en soudage par résistance - Partie 3:
Tore de mesure de courant (ISO 17657-3:2005)
Ta slovenski standard je istoveten z: EN ISO 17657-3:2007
ICS:
25.160.10 Varilni postopki in varjenje Welding processes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 17657-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2007
ICS 25.160.10
English Version
Resistance welding - Welding current measurement for
resistance welding - Part 3: Current sensing coil (ISO 17657-
3:2005)
Soudage par résistance - Mesurage des courants en Widerstandsschweißen - Schweißstrommessung für das
soudage par résistance - Partie 3: Tore de mesure de Widerstandsschweißen - Teil 3: Strommessspule (ISO
courant (ISO 17657-3:2005) 17657-3:2005)
This European Standard was approved by CEN on 19 May 2007.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17657-3:2007: E
worldwide for CEN national Members.

Foreword
The text of ISO 17657-3:2005 has been prepared by Technical Committee ISO/TC 44 "Welding and allied
processes” of the International Organization for Standardization (ISO) and has been taken over as EN ISO
17657-3:2007 by Technical Committee CEN/TC 121 "Welding", the secretariat of which is held by DIN.
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 December 2007, and conflicting national standards shall be withdrawn
at the latest by December 2007.
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, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 17657-3:2005 has been approved by CEN as a EN ISO 17657-3:2007 without any
modification.
INTERNATIONAL ISO
STANDARD 17657-3
First edition
2005-09-15
Resistance welding — Welding current
measurement for resistance welding —
Part 3:
Current sensing coil
Soudage par résistance — Mesurage des courants en soudage par
résistance —
Partie 3: Tore de mesure de courant

Reference number
ISO 17657-3:2005(E)
©
ISO 2005
ISO 17657-3:2005(E)
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ii © ISO 2005 – All rights reserved

ISO 17657-3:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Physical environment and operating conditions . 2
5 Classification of current sensing coils and designation of product . 2
5.1 Class of current sensing coils. 2
5.2 Standard values of the conversion coefficient. 2
5.3 Designation of products. 3
6 Requirements for current sensing coils. 3
6.1 Current sensing coil and connecting lead . 3
6.2 Conversion coefficient. 3
6.3 Measuring accuracy. 4
6.4 Mechanical strength. 4
6.5 Setting position error . 4
6.6 Influence of ambient temperature . 4
6.7 Thermal property of cover materials . 4
6.8 Test. 4
7 Test procedures. 5
7.1 Conversion coefficient. 5
7.2 Measuring accuracy. 6
7.3 Mechanical tests. 6
7.4 Setting position error test. 8
7.5 Thermal test. 8
7.6 Contact test. 8
8 Marking. 8
Annex A (informative) Design of current sensing coils . 9
Annex B (informative) Governing parameters of the conversion coefficient . 12
Annex C (informative) Type of current sensing coils and their recommended specification range. 13
Annex D (informative) Frequency response of current sensing coils . 17

ISO 17657-3:2005(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17657-3 was prepared by Technical Committee ISO/TC 44, Welding and allied processes, Subcommittee
SC 6, Resistance welding.
ISO 17657 consists of the following parts, under the general title Resistance welding — Welding current
measurement for resistance welding:
 Part 1: Guidelines for measurement
 Part 2: Welding current meter with current sensing coil
 Part 3: Current sensing coil
 Part 4: Calibration system
 Part 5: Verification of welding current measuring system
iv © ISO 2005 – All rights reserved

ISO 17657-3:2005(E)
Introduction
Requests for official interpretations of any aspect of this part of ISO 17657 should be directed to the
Secretariat of ISO/TC 44/SC 6 via your national standards body. A complete listing of these bodies can be
found at http://www.iso.org.
INTERNATIONAL STANDARD ISO 17657-3:2005(E)

Resistance welding — Welding current measurement for
resistance welding —
Part 3:
Current sensing coil
1 Scope
This part of ISO 17657 specifies current sensing coils of the toroidal-coil type as a current sensor for welding
current meters or a welding current measuring system used to monitor the welding current in resistance
welding, and is applicable for both current types, i.e. alternating current of 50 Hz or 60 Hz and direct current.
2 Normative references
The following referenced documents are indispensable for the application 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 669, Resistance welding — Resistance welding equipment — Mechanical and electrical requirements
ISO 17657-4, Resistance welding — Welding current measurement for resistance welding — Part 4:
Calibration system
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 669 and the following apply.
3.1
current sensing coil (toroidal coil)
multi-wound coil, in which wire is wound around a non-magnetic core of constant cross-section, used for
detecting the magnetic flux generated by current
NOTE The coil is mounted around or encircles a conductor through which the current to be measured passes.
3.2
reference current sensing coil
current sensing coil calibrated at a higher accuracy than the highly accurate class defined in this part of
ISO 17657
3.3
conversion coefficient
ratio of output voltage from a current sensing coil against the welding current, expressed in millivolts per
kiloamp (mV/kA)
NOTE The value is proportional to the frequency of the measured current, and is defined with a perfectly full-wave
current of 50 Hz as the test current.
ISO 17657-3:2005(E)
3.4
frequency response
feature indicating the influence of frequency of test current on the conversion coefficient
3.5
accuracy
scatter and deviation of the conversion coefficient
NOTE The output load of the current sensing coil strongly influences the value of the conversion coefficient. If the
output load and/or input impedance of an integrator changes, the conversion coefficient may deviate even though both
devices have been separately calibrated in a highly accurate class.
4 Physical environment and operating conditions
Unless otherwise specified, the current sensing coil shall be capable of operating under the following
conditions:
 at an ambient air temperature between +5 °C and +40 °C;
 in relative humidity up to 95 %;
 at altitudes up to 1 000 m above mean sea level;
 where gas, fine dust, oil mist, spatters, etc. are included in the air such as those caused by ordinary arc or
spot welding work.
When the operating conditions are not of any of those specified above, an agreement may be needed
between the manufacturer and the purchaser.
5 Classification of current sensing coils and designation of product
5.1 Class of current sensing coils
The current sensing coils shall be classified depending on construction, conversion coefficient and measuring
accuracy. Classifications by the accuracy are shown in Table 1.
Table 1 — Classification of current sensing coils
Classification Measuring accuracy Application
Highly accurate class ± 0,5 % of full scale Laboratory use
Accurate class ± 1,0 % of full scale Routine use for highly accurate systems
Ordinary class ± 3,0 % of full scale Routine use for ordinary systems

5.2 Standard values of the conversion coefficient
Rated values of the standard conversion coefficient, K, shall be of 150 mV/kA, 220 mV/kA and 1,5 V/kA for
full-wave alternating current of 50 Hz.
NOTE If a different test frequency is used for defining the conversion coefficient, the value can be converted by using
equation (1) described in 7.1.
2 © ISO 2005 – All rights reserved

ISO 17657-3:2005(E)
5.3 Designation of products
The following shall be indicated:
 design type as designated by type of construction;
 conversion coefficient;
 specified accuracy class;
 coil size (length for flexible type, and inner diameter for rigid type).
The designation of length can be omitted if the value is not needed.
EXAMPLE 1 Flexible type of 800 mm length, conversion coefficient of 150 mV/kA at 50 Hz, and accurate class.
Flexible (800 mm) 150 mV/kA, 50 Hz, class 1.0
EXAMPLE 2 Rigid type of 200 mm inner diameter, conversion coefficient of 180 mV/kA at 60 Hz, and highly accurate
class.
Rigid (200 mm) 180 mV/kA, 60 Hz, class 0.5
6 Requirements for current sensing coils
6.1 Current sensing coil and connecting lead
The current sensing coil, connector and connecting lead from the coil to the integrator/amplifier shall be
designed such that the coil is sensitive only to magnetic flux generated by current flow through the conductor
within the coil. Any external magnetic flux across the coil is not measured. The output of the coil is
proportional to a derivative of the measured current waveform.
If a flexible or rigid hatched-type coil is used, both ends of the sensing coil shall be fixed leaving little or no
space between the ends. To avoid wave distortion, the connecting lead and connector should be protected
from magnetic flux and should have low inductance.
A low inductive resistance shall be connected to the ends of the connecting lead as the output load, R . The
L
value should be constant between 200 Ω and 1 kΩ.
6.2 Conversion coefficient
The rated conversion coefficient of current sensing coils should conform with those described in 5.2. The
values shall be checked, and adjusted according to
...