ISO 21494:2019

Space systems - Magnetic testing

ISO 21494:2019 specifies magnetic test methods including magnetic field test methods, magnetic moment test methods, magnetization and demagnetization test methods and magnetic compensation test methods. This document is applicable to magnetic tests on several levels: spacecraft-level, subsystem-level and unit-level. ISO 21494:2019 gives guidelines for conducting magnetic tests both in zero-magnetic field environment provided by magnetic test facilities and in the presence of the geomagnetic field environment.

Systèmes spatiaux — Essais magnétiques

General Information

• Status: Published
• Publication Date: 21-Feb-2019
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 14 - Space systems and operations
• Drafting Committee: ISO/TC 20/SC 14/WG 2 - System requirements, verification and validation, interfaces, integration, and test
• Current Stage: 9092 - International Standard to be revised
• Start Date: 25-Feb-2025
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO/TS 23758:2021 - Guidelines for the validation of qualitative screening methods for the detection of residues of veterinary drugs in milk and milk products
• Effective Date: 06-Jun-2022

Overview

ISO 21494:2019 - Space systems - Magnetic testing defines standard magnetic test methods for spacecraft, subsystems and units. The standard specifies procedures for magnetic field tests, magnetic moment measurements, magnetization and demagnetization tests, and magnetic compensation. It covers testing both in a controlled zero‑magnetic field (e.g., coil-based facilities) and in the presence of the geomagnetic field, and includes informative annexes with procedures and calculation formulas.

Key SEO phrases: ISO 21494, magnetic testing, spacecraft magnetic cleanliness, magnetic moment, magnetization, demagnetization, magnetic compensation.

Key topics and requirements

• Test scope and levels: Applicable at spacecraft‑level, subsystem‑level and unit‑level to validate magnetic behavior across integration stages.
• Magnetic test methods: Standardized methods for measuring magnetic fields and dipole moments (remnant, stray and induced).
• Magnetization/demagnetization: Procedures for intentionally magnetizing or demagnetizing hardware using coil systems and documenting resulting fields and moments.
• Magnetic compensation: Methods to reduce spacecraft magnetic signature (e.g., using compensation magnets or design/layout mitigation) and verification testing after compensation.
• Test environments and facilities: Guidance for using main coil systems (Helmholtz/Braunbeck type) to create zero‑magnetic or controllable magnetic fields, and for testing in the natural geomagnetic field.
• EUT (Equipment Under Test) requirements: Implementing a magnetic cleanliness control plan, allocation of magnetic moment budgets, material selection (avoid hard magnetic materials; limit soft magnetic materials), and design practices to minimize stray fields.
• Test sequence and reporting: Recommended test flow (initial measurements, magnetization, post‑magnetization measurements, demagnetization, compensation, and final verification) and requirements for the test report. Annexes A–D provide procedural detail and formulas.

Applications and users

ISO 21494 is essential for:

• Space systems engineers and spacecraft systems integrators validating attitude control and payload interference limits.
• Mission planners and payload teams (especially magnetometer and plasma instrument teams) requiring magnetic cleanliness.
• Test laboratories and facilities performing zero‑field and geomagnetic testing.
• Quality, verification and acceptance teams defining magnetic test campaigns and compliance evidence.
• Component and materials engineers selecting non‑magnetic or low‑coercivity materials to meet magnetic budgets.

Practical benefits include ensuring attitude stability (reduced magnetic torque), protecting magnetically sensitive scientific instruments, and demonstrating compliance with mission magnetic requirements.

Related standards

• ISO 14644‑1 (Cleanrooms and associated controlled environments - classification by particle concentration) - referenced in ISO 21494 for test room cleanliness.
• ISO/IEC Directives (editorial and development rules referenced in the standard foreword).

Keywords reinforced: spacecraft magnetic testing, magnetic cleanliness control, magnetic test facility, magnetic moment measurement.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21494
First edition
2019-02
Space systems — Magnetic testing
Systèmes spatiaux — Essais magnétiques
Reference number
©
ISO 2019
© ISO 2019
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
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Phone: [phone]
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Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 3
5 Requirements . 3
5.1 EUT requirements . 3
5.2 Test requirements . 4
6 Test items . 4
7 Test room environments . 5
8 Magnetic field test methods . 5
8.1 Test purpose . 5
8.2 Test facilities. 5
8.3 Procedures for magnetic field test . 6
9 Magnetic moment test methods . 6
9.1 Test purpose . 6
9.2 Test facilities. 6
9.3 Procedures and calculating formulas for magnetic moment test . 7
9.4 Magnetic moment test in the geomagnetic field . 7
10 Magnetization and demagnetization test methods . 7
10.1 Test purpose . 7
10.2 Test facilities. 7
10.3 Procedures for magnetization and demagnetization test . 8
11 Magnetic compensation test method . 8
11.1 Test purpose . 8
11.2 Procedures for magnetic compensation test . 9
12 Test report . 9
Annex A (informative) Procedures for a magnetic field test .10
Annex B (informative) Procedures and calculating formulas for a magnetic moment test .13
Annex C (informative) Procedures for a magnetization and demagnetization test .24
Annex D (informative) Procedures for a magnetic compensation test .26
Bibliography .27
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 documents 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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
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 Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
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 2019 – All rights reserved

Introduction
The magnetic torque, which is created by the interaction between a geomagnetic field and the remnant
magnetic moment of the spacecraft, has considerable disturbance on the flight attitude of the spacecraft.
The magnetic field of the spacecraft itself will affect a magnetometer scientific payload sensitive to
spacecraft-induced magnetic fields. Thus, magnetic tests on Earth-orbiting or interplanetary spacecraft
missions with very stringent requirements on magnetic cleanliness are needed in order to ensure that
the spacecraft’s inherent magnetic properties meet the design goals.
This document provides magnetic test requirements and methods for measuring and evaluating
magnetic properties of the spacecraft. The magnetic test methods outlined in this requirements
document are effective enough to verify the compliance of magnetic requirements imposed on the
spacecraft and to ensure the success of spacecraft flight missions free of magnetic interference and
magnetic contamination due to magnetic materials and induced current-generated magnetic fields of
the spacecraft.
INTERNATIONAL STANDARD ISO 21494:2019(E)
Space systems — Magnetic testing
1 Scope
This document specifies magnetic test methods including magnetic field test methods, magnetic
moment test methods, magnetization and demagnetization test methods and magnetic compensation
test methods. This document is applicable to magnetic tests on several levels: spacecraft-level,
subsystem-level and unit-level.
This document gives guidelines for conducting magnetic tests both in zero-magnetic field environment
provided by magnetic test facilities and in the presence of the geomagnetic field environment.
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 14644-1, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness
by particle concentration
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological 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
equipment under test
EUT
object under the magnetic test on system, subsystem or unit level generally
3.2
remnant magnetic moment
magnetic moment of the EUT in a zero-magnetic field environment when the EUT is not in a powered on
operational mode, that is mostly due to the residual magnetic fields from spacecraft materials
3.3
stray magnetic moment
magnetic moment of the EUT in zero-magnetic field environment when the EUT is in a powered on
operational mode
3.4
induced magnetic moment
additional magnetic moment of the EUT generated in an external magnetic field environment when the
EUT is not in a powered on operational mode, that is mostly due to soft magnetic materials that easily
magnetize in an external magnetic field
3.5
remnant magnetic field
magnetic field produced by the remnant magnetic moment of the EUT as measured at a distance from
the magnetic moment location and falls off as the inverse cube of the distance from the magnetic
moment location
3.6
stray magnetic field
magnetic field produced by the stray magnetic moment of the EUT in a powered on operational mode
3.7
induced magnetic field
magnetic field produced by the induced magnetic moment of the EUT and mostly due to soft magnetic
materials that easily magnetize in an external magnetic field
3.8
zero-magnetic field
magnetic field within a certain volume reduced to very low levels when the geomagnetic field is
compensated by a cancelling magnetic field provided by a typical main coil system such as a Helmholtz
coil or Braunbeck coil system
3.9
controllable magnetic field
magnitude of magnetic field within a certain volume that is controlled by adjusting electric current of a
typical main coil system such as a Helmholtz coil or Braunbeck coil system
3.10
magnetization field
magnetic field used for magnetization tests of the EUT when exposed to a uniform and steady magnetic
field for a certain period of time and provided by a magnetization and demagnetization coil system
3.11
demagnetization field
magnetic field used for demagnetization tests of the EUT by exposing them in an alternating sinusoidal
magnetic field with a continuously attenuated amplitude and provided by a magnetization and
demagnetization coil system
3.12
main coil system
coil system, usually composed of Helmholtz or Braunbeck coils and energized by power supplies, that
can provide a zero-magnetic field environment within a given volume of the coil system or that can
generate a controllable magnetic field environment by applying the system with calibrated electric
current levels
3.13
magnetization and demagnetization coil system
coil system, usually composed of a Helmholtz coil and energized by power supplies, that can provide
magnetization and demagnetization fields by applying the system with electric current
3.14
magnetic field stability
variation of the magnetic field at the same location during a certain period
3.15
magnetic field homogeneity
ratio (given in %) of the maximum magnetic field deviation in the volume divided by the magnetic field
at the centre of the volume, or the range (given in ± values) of the maximum magnetic field deviation in
the volume
2 © ISO 2019 – All rights reserved

3.16
homogeneous volume of magnetic field
spatial volume that satisfies the requirement of magnetic field homogeneity
3.17
soft magnetic material
ferromagnetic material with low field strength (coercivity) that can be magnetized and
demagnetized easily
EXAMPLE Invar and Kovar materials.
3.18
hard magnetic material
ferromagnetic material with high field strength (coercivity) that cannot be demagnetized easily
EXAMPLE Permanent magnets.
3.19
compensation magnet
permanent magnet used for magnetic compensation
4 Abbreviated terms
EUT Equipment Under Test
IMF Initial Magnetic Field
RMF Remnant Magnetic Field
SMF Stray Magnetic Field
IDMF Induced Magnetic Field
IMDM Initial Magnetic Dipole Moment
RMDM Remnant Magnetic Dipole Moment
SMDM Stray Magnetic Dipole Moment
IDMDM Induced Magnetic Dipole Moment
MFAM Magnetic Field After Magnetization
MFAD Magnetic Field After Demagnetization
MDMAM Magnetic Dipole Moment After Magnetization
MDMAD Magnetic Dipole Moment After Demagnetization
5 Requirements
5.1 EUT requirements
When a spacecraft requires the protection of a magnetic sensitive payload such as a magnetometer
sensor or plasma search coil and the control of magnetic torque for attitude control, a magnetic
cleanliness control plan shall be instituted based on properties and constraints, which are related to
mission objectives. This plan should:
a) Prepare magnetic control guidelines, outlining examples on how to control magnetic materials,
what materials are acceptable, how to perform tests and to model the overall spacecraft based on
magnetic moment results.
b) Establish a magnetic moment budget or allocation list for parts, units, subsystems and spacecraft
in the actual magnetic field environment on the orbit, such as the magnetic moment or field of the
EUT at low levels of magnetic field and the delta of magnetic moment or field between unpowered
and powered mode.
c) Include the steps for reducing magnetic sources. Outline of detailed proven methods for the
reduction and cancellation of magnetic fields, elimination of magnetic materials replaced with non-
magnetic materials etc.
d) Define magnetic test methods and requirements for parts, units, subsystems and spacecraft.
The steps for reducing magnetic sources include avoiding hard magnetic materials, limiting the use
of soft magnetic materials, applying self-compensating configuration of magnetic sources, designing
all current carrying and electrical grounding elements to minimize stray magnetic field and stray
magnetic moment by self-cancelling methods including solar array backwiring.
5.2 Test requirements
In order to check and control the magnetic properties of the EUT, the magnetic test should be conducted.
An example of magnetic test flow is:
a) IMF and IMDM measurement.
b) Magnetization test.
c) MFAM and MDMAM measurement.
d) Demagnetization test.
e) MFAD and MDMAD measurement.
f) Magnetic compensation test.
g) RMF, SMF, RMDM and SMDM measurement after magnetic compensation.
h) IDMF and IDMDM measurement.
References [1]–[5] recommend the magnetic test requirements.
6 Test items
Magnetic test items described in this document refer to magnetic field test, magnetic moment test,
magnetization test, demagnetization test and magnetic compensation test.
Magnetic test items are tailored based upon magnetic test requirements for each unique mission or
plan. The logic flow of test items is defined according to magnetic requirements imposed for each
specific spacecraft.
The magnetic field of the spacecraft will affect precision measurements of magnetic sensitive payload
such as magnetometers or plasma wave search coils. Therefore, the spacecraft has requirements
on magnetic cleanliness imposed by the sensitivity of the scientific payloads requiring low levels of
magnetic fields. According to the requirements, the magnetic field test shall be conducted to predict
magnetic cleanliness level of the spacecraft with the goal of meeting the reduced magnetic field levels
needed by the sensitive payloads.
4 © ISO 2019 – All rights reserved

The magnetic disturbance torque acting on the spacecraft is equal to the cross-product of the
remnant magnetic moment of the spacecraft and the ambient magnetic flux density. If required, the
magnetic moment test shall be conducted to predict the flight attitude changes caused by the magnetic
disturbance torque of the spacecraft.
Magnetization and demagnetization tests shall be conducted if the spacecraft is easily influenced by
the external magnetic fields while on the orbit. Demagnetization tests shall be conducted as a final
step in the magnetic testing process well before its launching if the spacecraft may have inadvertently
become magnetized after the magnetic tests.
Magnetic compensation tests shall be conducted if the magnetic properties of the spacecraft do not
satisfy the overall magnetic cleanliness requirements.
The spacecraft-level magnetic tests for qualification and acceptance are recommended to be conducted
after the vibration test. This provides an opportunity to eliminate or reduce any magnetization of
the flight hardware caused by the magnetic fields associated with the vibration shaker test facilities,
especially for a spacecraft with magnetically sensitive payloads.
References [6]–[7] provide examples of actual implementation of the approach in recent missions
requiring magnetic cleanliness.
7 Test room environments
The requirements of test room environments are as follows:
a) Temperature, cleanliness and humidity shall meet customer’s requirements.
b) The air cleanliness in test room shall comply with ISO 14644-1.
8 Magnetic field test methods
8.1 Test purpose
The purpose of magnetic field test is to measure and evaluate magnetic field of the EUT and verify
whether it conforms to magnetic field requirements of the EUT.
Magnetic field test methods include RMF, SMF and IDMF measurements of the locations sensitive to
magnetic field on the EUT and RMF, SMF and IDMF distribution measurements on a sphere around
the EUT.
RMF is mainly generated by magnets, electro-magnets in off-state or residual perm-up (or
magnetization) due to hysteresis of soft magnetic materials in the EUT. SMF is generated by electric
current flowing within the EUT when in a powered on operational mode. RMF and SMF are independent
of the environmental magnetic field. RMF and SMF tests should be conducted in zero-magnetic field.
IDMF is mainly generated by the soft magnetic materials in the EUT. If an external magnetic field is
applied to the EUT, the magnetic field measurement result of the EUT may be different in zero-magnetic
field. This difference is called IDMF. IDMF disappears when the external field is ceased. IDMF test should
be conducted in the controllable magnetic field.
8.2 Test facilities
The test facilities are mainly composed of the main coil system, turntable, fixtures/brackets and
magnetic field measuring instruments or test magnetometer sensors. The main coil system shall be
able to provide the zero-magnetic field or controllable magnetic field within a given volume where the
EUT will be located in the centre of the turntable. The controllable magnetic field also can be provided
by the additional coil system. The main coil system access opening shall be large enough to allow the
transit of the EUT and its non-magnetic fixture and/or holding brackets into the zero-magnetic field
volume. The magnitude, homogeneity and stability of the zero-magnetic field and the controllable
magnetic field shall satisfy test requirements.
The turntable shall be rotated from 0° to 360° along the vertical axis, with all angles easily identifiable.
The ball bearing capacity of the turntable shall be more than the total weights of the EUT and its fixed
bearing. Proof loading of the turntable shall be conducted prior to the test to ensure proper rotation
without galling the bearings. The turntable is not required for the magnetic field measurement of
locations sensitive to magnetic field on the EUT. The turntable shall be required for the magnetic field
distribution measurement on a sphere around the EUT.
The test facilities shall be made of non-magnetic materials. Copper, aluminium, titanium, brass, treated
wood and other non-metallic materials are recommended.
The fluxgate magnetometers are recommended for measuring the magnetic field of the EUT. The
measurement range and resolution of the magnetometers should be adapted to the required results
and accuracy of the magnetic test.
The test facilities and measurement instruments shall be calibrated periodically or in advance of testing
and used during its useful-life.
8.3 Procedures for magnetic field test
Two procedures for magnetic field test methods in Annex A are provided as examples: (1) test
procedure for locations sensitive to magnetic field on the EUT and (2) test procedure for magnetic field
distribution measurement on a sphere around the EUT. The procedures for the magnetic field test shall
be selected according to magnetic test requirements.
9 Magnetic moment test methods
9.1 Test purpose
The purposes of magnetic moment tests are to measure and evaluate magnetic moments of the EUT and
verify whether it conforms to magnetic moment requirements of the EUT.
The magnetic dipole moment is the major part of the magnetic moment of the EUT, so magnetic moment
test methods include RMDM, SMDM and IDMDM measurements of magnetic dipole method, near-field
method and multiple magnetic dipole method.
RMDM is generated by magnets, electro-magnets in off-state or residual perm-up (or magnetization)
due to hysteresis of soft magnetic materials in the EUT. SMDM is generated by electric current flowing
within the EUT. RMDM and SMDM are independent of the environmental magnetic field. RMDM and
SMDM tests are conducted in the zero-magnetic field or geomagnetic field.
IDMDM is the induced magnetic dipole moment in soft magnetic materials caused by an external
magnetic field. This magnetic moment contribution changes instantaneously with the magnitude and
the direction of the external magnetic field. IDMDM test is conducted in the controllable magnetic field.
9.2 Test facilities
The test facilities and measurement instruments for the magnetic moment test in zero-magnetic field
shall be the same as those described in 8.2 for the magnetic field test.
The turntable is not required for the magnetic moment measurement of the magnetic dipole method.
The turntable shall be required for the magnetic moment measurement with the near-field method and
multiple magnetic dipole modelling method.
The main coil system shall be unnecessary for the magnetic moment test in the geomagnetic field. The
turntable, fixture/bracket and measurement instruments shall be the same as those described in 8.2.
6 © ISO 2019 – All rights reserved

9.3 Procedures and calculating formulas for magnetic moment test
The procedures and calculating formulas for three magnetic moment test methods (magnetic dipole
method, near-field method and multiple magnetic dipole modelling method) shown in Annex B may be
used as examples.
The magnetic dipole method is usually used to obtain a rough magnetic moment of the EUT. The near-
field method is one of spherical harmonics analysis methods and shall test magnetic dipole moment
of the EUT more precisely. The multiple magnetic dipole modelling method is a precise method too.
Procedures and calculating formulas for magnetic moment tests shall be selected according to magnetic
test requirements.
The magnetic dipole method is commonly used for RMDM, SMDM and IMDM measurements of the EUT.
The near-field method and multiple magnetic dipole modelling method are commonly used for RMDM
and SMDM measurement of the EUT.
9.4 Magnetic moment test in the geomagnetic field
Magnetic moment test for RMDM and SMDM measurements may be conducted in the geomagnetic field.
Magnetic moment test methods in the geomagnetic field may be used for the EUT where the precision
requirement of the measuring result is not high.
The magnetic field induced may be generated by soft magnetic materials of the EUT in the geomagnetic
field. When the magnetic moment test is conducted in the geomagnetic field, the magnetic fields
induced in the geomagnetic field will have some effect on the measuring results. Magnetic moment test
may be conducted in the geomagnetic field for the EUT, under the condition that the EUT contains a
sufficiently small amount of soft magnetic material and other magnetic material is hard enough such
that only negligible small changes of the remnant magnetization occur in the environmental field. If the
magnetic field induced in the geomagnetic field is larger than remnant magnetic field of the EUT, it is
better that the measurement method needs to be adapted to eliminate the magnetic field induced in the
geomagnetic field from the calculation for the magnetic moment of the EUT.
The magnetic moment test conducted in the geomagnetic field may be influenced by environmental
magnetic field perturbations. During magnetic tests, no other magnetic sources are allowed to be close
to the fluxgate sensors on the magnetic test site. Environmental magnetic field perturbations may be
monitored and eliminated from the calculation for the magnetic moment of the EUT.
10 Magnetization and demagnetization test methods
10.1 Test purpose
The EUT is magnetized for determining the EUT history of magnetic field exposures. The EUT is
demagnetized for the removal of the effects of any previous exposures in environmental magnetic field.
The magnetization and demagnetization test is critical for some scientific payloads such as plasma
wave search coils, ultra-stable oscillators and magnetometers. Therefore, the need for magnetization
and demagnetization test shall be justified.
The test sequence, which is used to inspect the magnetic stability of the EUT, is IMF or IMDM
measurements to be the first. Then the EUT is magnetized and MFAM or MDMAM is measured. Finally,
the EUT is demagnetized and MFAD or MDMAD is measured. Comparisons between the measuring
results after magnetization and demagnetization give susceptible level of magnetic contamination for
the EUT.
10.2 Test facilities
The facilities of magnetization and demagnetization are mainly composed of a main coil system, a
magnetization and demagnetization coil system, a turntable, fixtures/brackets and magnetic field
measuring instruments. The main coil system, turntable and fixtures/brackets for magnetization and
demagnetization tests shall be the same as those described in 8.2 for the magnetic field test.
The main coil system shall be unnecessary if the magnetization and demagnetization coil system is
equipped with supplementary geomagnetic field compensation coils for required directions.
The magnetization and demagnetization coil system shall be able to provide a steady (i.e. static)
magnetic field for magnetization and an alternating sinusoidal and slowly decaying magnetic field
for demagnetization. The coil system access opening shall be sufficiently large that the EUT and its
fixture and bracket can be brought into the centre of the coil system. Magnitude and duration of
the magnetization field shall be adjustable. Maximum amplitude, frequency and duration of the
demagnetization field shall be adjustable and the decrease in amplitude of the demagnetization field
shall be set linear or exponential. For example, a wave form of a sinusoidal demagnetization field,
whose amplitude is increased or decreased in linearity, is shown in Figure 1. Care shall be taken that
the alternating demagnetization field is bias-free and the final absolute field strength value, achieved
at the end of demagnetization loop, is much smaller than the geomagnetic field. The magnetization
and demagnetization coil system shall be made of non-magnetic materials. Copper, aluminium, brass,
titanium and non-metallic materials are recommended.
The Teslameter is recommended to measuring the magnetization field and demagnetization field.
The test facilities and measurement instruments shall be calibrated periodically or in advance of testing
and used during its useful-life.
Key
B magnetic field
Figure 1 — Sketch map of the demagnetization waveform
10.3 Procedures for magnetization and demagnetization test
The typical procedures for magnetization and demagnetization test are shown in Annex C.
11 Magnetic compensation test method
11.1 Test purpose
Small compensation magnets may be fixed at optimal locations on the EUT to minimize RMF and RMDM
of the EUT. Magnetic compensation with permanent magnets does not work for IDMF and IDMDM. SMF
and SMDM need dynamic compensation.
8 © ISO 2019 – All rights reserved

11.2 Procedures for magnetic compensation test
The typical procedures for magnetic compen
...