ISO 24631-3:2025

International
Standard
ISO 24631-3
Third edition
Radiofrequency identification of
2025-07
animals —
Part 3:
Evaluation of performance of RFID
transponders conforming with ISO
11784 and ISO 11785
Identification des animaux par radiofréquence —
Partie 3: Évaluation de la performance des transpondeurs RFID
conformes à l'ISO 11784 et à l'ISO 11785
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Conformance . 3
5 Abbreviated terms . 3
6 Application . 4
7 Test procedures . 4
7.1 General .4
7.2 Helmholtz configuration .5
7.2.1 Transponder parameter test set-up .5
7.2.2 Field strength calculation .5
7.2.3 Helmholtz transmitting antenna (HTA) coils .5
7.2.4 Helmholtz sensing coils (HSC) and sensing coils (SC) .5
7.2.5 Positioning HSC and SC in relation to HTA .8
7.2.6 Matching network (MN) .8
7.2.7 Matching network (MN) .9
7.2.8 Compensation network (CN) .10
7.3 Test apparatus.10
7.4 Test setups for measuring the modulation amplitude .11
7.4.1 FDX-B transponders .11
7.4.2 HDX transponders . 12
7.5 Test conditions . 12
7.6 Tests . 12
7.6.1 General . 12
7.6.2 Transponder orientation . 12
7.6.3 Constant magnetic field nulling . 13
7.6.4 Minimal activating magnetic field strength in FDX-B mode .14
7.6.5 Minimal activating magnetic field strength in HDX mode .14
7.6.6 Modulation amplitude in FDX-B mode . 15
7.6.7 Modulation amplitude in HDX mode .17
7.6.8 Bit length stability in FDX-B mode .19
7.6.9 Frequency stability in HDX mode . 22
Annex A (informative) Test application form (ISO 24631-3) .25
Annex B (informative) How to link the in ISO 24631-3 defined technical parameters to in field
applications .26
Bibliography .27

iii
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).
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 Technical Committee ISO/TC 23, Tractors and machinery for agriculture and
forestry, Subcommittee SC 19, Agricultural electronics.
This third edition cancels and replaces the second edition (ISO 24631-3:2017), which has been technically
revised.
The main changes are as follows:
— the former Annex B has been removed because the current source presented does not function;
— a new Annex B has been added to discuss the interpretation of the technical parameters.
A list of all parts in the ISO 24631 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
Introduction
ISO has appointed a registration authority (RA) competent to register manufacturer codes used in the
radiofrequency identification (RFID) of animals in accordance with ISO 11784 and ISO 11785.
The registration authority for ISO 11784 and ISO 11785 can found under https://www.iso.org/iso/home/
standards_development/list_of_iso_technical_committees/maintenance_agencies.htm.
This document deals with the performance of RFID transponders, of which the main types used for animal
identification are
— injectable transponders,
— electronic ear tag transponders,
— electronic ruminal bolus transponders,
— leg tag transponders, and
— tag attachments.
This document permits the characterization of the two RFID communication paths: the energy transfer from
transceiver to transponder and the data transfer from transponder to transceiver. This characterization can
be obtained from the results of two measurements: the first determining the minimal activating magnetic
field strength needed for transmitting the information and the second the transponder modulation
amplitude. Both measurements use a reference measurement antenna configuration under conditions
allowing the absolute values to be obtained for comparison of data between the tested transponders.
Additional measurements that contribute to the performance assessment of the transponders are
the bit length stability in the case of FDX-B transponders and the frequency stability in the case of HDX
transponders. These parameters can be measured using the same measurement antenna configuration.
The test procedures specified in this document are recognized by the Federation of European Companion
Animals Veterinary Association (FECAVA) and World Small Animal Veterinarian Association (WSAVA) and,
as such, can be applied also to companion animals.

v
International Standard ISO 24631-3:2025(en)
Radiofrequency identification of animals —
Part 3:
Evaluation of performance of RFID transponders conforming
with ISO 11784 and ISO 11785
1 Scope
This document provides the means of evaluating the performance of ISO 11784- and ISO 11785-conformant
radiofrequency identification (RFID) transponders used in the individual identification of animals. It defines
procedures of measuring technical parameters characterizing the performance of transponders.
In Annex B an explanation is given how to interpret these parameters and how to link them to infield
requirements.
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 11784, Radio frequency identification of animals — Code structure
ISO 11785, Radio frequency identification of animals — Technical concept
ISO 24631-1, Radiofrequency identification of animals — Part 1: Evaluation of conformance of RFID transponders
with ISO 11784 and ISO 11785 (including granting and use of a manufacturer code)
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/
3.2
activation field
electromagnetic field with a frequency of 134,2 kHz
3.3
bit length stability
stability of an FDX-B transponder (3.18) expressed by the standard deviation of the duration of one-bit
information
3.4
country code
three-digit numeric code representing a country in accordance with ISO 3166-1

3.5
frequency stability
stability of an HDX transponder (3.18) expressed by the standard deviation of the two frequencies
representing the low and high bit of an FSK-modulated signal
3.6
identification code
code used to identify the animal individually, at the national and, in combination with a country code (3.4),
international levels
Note 1 to entry: It is a national responsibility to ensure the uniqueness of national ID codes.
3.7
transceiver
transceiver (3.17) used to test the transponders (3.18) generating the activation field (3.2), able to read FDX-B
and HDX transponders
3.8
manufacturer
company that submits an application for conformance testing or for the granting and use of a manufacturer
code (3.9) for transponders (3.18) in conformance with ISO 11784 and ISO 11785 while accepting the
conditions set forth in ISO 24631-1:2017, Annexes B, C and E
3.9
manufacturer code
MFC
three-digit number granted by the RA to a manufacturer (3.8) under the conditions set forth in
ISO 24631-1:2017, Annex E, whose range and placement within the code structure are in accordance with
ISO 11784
Note 1 to entry: Only one manufacturer code is granted to the same manufacturer.
3.10
product code
six-digit number granted (and registered) by the registration authority (3.14) to a manufacturer (3.8) for
a certain type of transponder (3.18), formatted such that its first part is the manufacturer code (3.9) and
second part a three-digit serial number
3.11
RA-recognized test centre
accredited test centre meeting the criteria of the registration authority (3.14)
3.12
RA-registered transponder
transponder (3.18) registered on the website of the registration authority (3.14)
3.13
RA-registered manufacturer
manufacturer (3.8) registered by the registration authority with one or more RA-registered transponders (3.12)
3.14
registration authority
RA
entity that approves test laboratories and issues and registers manufacturer (3.8) and product codes (3.10)
3.17
transceiver
device used to communicate with the transponder

3.18
transponder
radio frequency identification (RFID) device that transmits its stored information when activated by a
transceiver (3.17) and that may be able to store new information
Note 1 to entry: See ISO 24631-1 for definitions of the main types.
3.19
transponder modulation amplitude
characterization of the transponder signal strength sent back to the transceiver (3.17)
Note 1 to entry: FDX-B corresponds to the modulation depth; HDX corresponds to the average voltage depth.
3.20
minimal activating magnetic field strength
minimal value of magnetic field strength needed to obtain full activity of the transponder
Note 1 to entry: The transponder is activated after having been placed in a magnetic field whose strength depends
on the antenna, chip and packaging design. Full activity is obtained when the transponder is supplied with energy
sufficient to transmit the complete data according to ISO 11785.
4 Conformance
Test centres recognized by the registration authority (RA) shall perform transponder testing using the
procedures specified in Clause 7 and shall report the test results to the RA. These tests are in accordance
with the technical requirements of ISO 11784 and ISO 11785. The manufacturer shall apply for transponder
testing by completing and submitting to the RA the application form provided in Annex A. Only transponders
with a product code issued by the RA (see ISO 24631-1) shall be tested. A transponder test report shall be
accorded to a manufacturer whose transponder product has been tested as per Clause 7.
5 Abbreviated terms
CN compensating network
CRC cyclic redundancy check
FDX-B full duplex communication protocol (conforming to ISO 11785, excluding protocols mentioned in
ISO 11785:1996, Annex A)
FSK frequency shift keying
HDX half duplex communication protocol
HSC Helmholtz sensing coil
HTA Helmholtz transmitting antenna
IEEE Institute of Electrical and Electronics Engineers
MFC manufacturer code
MN matching network
RA registration authority
RFID radiofrequency identification
SC sensing coil
TUT transponder under test
6 Application
6.1 The application submitted to the RA for testing the performance of a transponder shall consist of a
covering letter and the application form presented in Annex A. The RA shall confirm receipt of the application
to the manufacturer within 2 weeks. By signing the application form, the manufacturer agrees to fulfil the
provisions of this document.
6.2 Approval in accordance with ISO 24631-1 is a prerequisite for approval for testing in accordance with
this document (RA-registered manufacturer and RA-registered transponder).
6.4 The RA maintains a list of recognized test centres, from which the manufacturer may choose the
centre that will test his transponder product.
NOTE Test centres that conform with ISO/IEC 17025 for the measurements defined in this document can be
recognized by the RA.
6.5 The manufacturer shall provide the RA-recognized test centre with 50 transponders of the same
type and model for testing. If the RA-recognized test centre selected already has this number of the same
transponders (transponders the manufacturer has sent to and were tested by the RA-recognized test centre
for obtaining RA-registration transponder), they may be used. The transponders shall carry the country
code “999” (indicating a test transponder) or the manufacturer’s code if existent. The manufacturer may
freely choose the identification codes, but duplicated numbers are not allowed. The manufacturer shall
provide a list of the transponder codes in decimal representation.
6.6 The RA-recognized test centre shall verify the transponders using the test procedures specified in
Clause 7. All tested transponders shall be readable by the configuration also specified in Clause 7. The codes
read shall match the codes provided by the manufacturer.
6.7 The RA-recognized test centre shall prepare a confidential report of the results and shall send two
copies (or an electronic version) of the report to the chairman of the RA.
6.8 The RA chairman shall inform the manufacturer of the test results in a letter together with a copy of
the report.
6.9 The tested transponders shall be kept by the RA-recognized test centre, under the ownership of the RA.
6.10 The RA shall make publicly available a photograph of the registered transponder.
6.11 The RA shall make publicly available the main results of the test. A manufacturer shall have the right
to refuse that the results be made publicly available or to request their withdrawal from public availability.
In the first case, the manufacturer shall send a request to the RA not to publish, within two weeks of having
received the test report. In the second, the manufacturer shall send a request to the RA and the RA shall
remove the results from public availability within four weeks of receipt of this request.
6.12 The RA shall do everything within its power to protect the integrity of this procedure with regard to
ISO 11784 and ISO 11785.
7 Test procedures
7.1 General
The test centre shall test five transponders randomly picked from the 50 transponders provided by the
manufacturer, in accordance with the following procedures. During the measurements, the transponder
shall be positioned in a Helmholtz configuration producing an adjustable uniform magnetic field.

7.2 Helmholtz configuration
7.2.1 Transponder parameter test set-up
The Helmholtz transmitting antennas (HTA) produce a homogeneous, cylindrically shaped field. A functional
diagram of the Helmholtz configuration and corresponding test setup is shown in Figure 1. The transponder
under test (TUT) shall be positioned on the central axis, centred between the transmitter coils of the test
1)
configuration. The matching network (MN) shall be used to match the setup of the two HTA to 50 Ω output
resistance of the amplifier.
7.2.2 Field strength calculation
A very accurate relation exists between the magnetic field and the current in the Helmholtz coils.
By measuring the current through the HTA, the magnetic field strength, H (root mean square,
rms
35,8 mA/m to 35,8 A/m) can be calculated from Formula (1):
NU×
HTAHTA_pp
H = (1)
rms
1,9764××d R
HTAHTA
where
N is the number of turns on HTA coil (= 5);
HTA
U is the peak-to-peak voltage at R ;
HTA_pp HTA
d is the diameter of HTA coil;
HTA
R is the resistor in series with HTA coils.
HTA
7.2.3 Helmholtz transmitting antenna (HTA) coils
The dimensions and characteristics of the HTA coils shall be as shown in Figure 2.
Two HTA coils are used in the Helmholtz configuration.
Owing to the low number of turns (five), the best way to manufacture the HTA is by winding onto a core
element.
7.2.4 Helmholtz sensing coils (HSC) and sensing coils (SC)
HSC shall be used for both FDX-B and HDX. Two HSC shall be connected in series.
The HSC and the SC shall be made in accordance with Figure 3 and shall be connected by means of the
compensation network (CN) (see Figure 1).
1) The maximum size of the transponder is limited by the Helmholtz configuration's dimensions — in length by the
distance between the HTA coils, and in diameter by the HSC diameter. The signal emitted by small transponders can
require smaller sensing coil dimensions. If that is the case, the ISO/TC 23/SC 19 animal identification working group will
develop a special setup for those devices.

Key
1 code generator
2 function waveform or arbitrary waveform generator
3 oscilloscope
4 amplifier
5 personal computer (PC) with IEEE card
6 measurement antenna configuration
CN compensation network
e
HSC1 first Helmholtz sensing coil
e
HSC2 second Helmholtz sensing coil
e
HTA1 first Helmholtz transmitting antenna
e
HTA2 second Helmholtz transmitting antenna
MN matching network
SC sensing coil
TUT transponder under test
a
Trigger.
b
IEEE interface.
c
Output signal.
d
50 Ω.
e
Serial and in phase.
Figure 1 — Test setup and Helmholtz configuration

Dimensions in millimetres
Key
1 core element
a
d
i,HTA.
b
d
e,HTA.
c
I
HTA.
NOTE 1 Wire: B155 500 µm Grade 1B.
NOTE 2 N (number of turns on HTA) = 5.
HTA
Figure 2 — HTA coils — Physical characteristics
Dimensions in millimetres
a
d .
i,HSC
b
I .
HSC
NOTE 1 Wire: B155 100 µm Grade 1B or P155 100 µm Grade 2.
NOTE 2 N (number of turns on HSC) = 70.
HSC
NOTE 3 N (number of turns on SC) = 45.
SC
Figure 3 — HSC and SC — Physical characteristics

7.2.5 Positioning HSC and SC in relation to HTA
The HSC shall be centred between the two HTA. The external SC, if needed, shall be positioned as shown in
Figure 4.
Dimensions in millimetres
Key
1 ferrite coil
2 air coil
CN compensation network
HSC1 first Helmholtz sensing coil
HSC2 second Helmholtz sensing coil
HTA1 first Helmholtz transmitting antenna
HTA2 second Helmholtz transmitting antenna
MN matching network
SC sensing coil
Figure 4 — HTA, HSC and SC positions
7.2.6 Matching network (MN)
The matching network shall be realized according to Figure 5 (see also Figure 1).

Key
C1, C2 capacitors
HTA1, HTA2 Helmholtz transmitting antennas
U voltage at RHTA
RHTA
RHTA resistor in series with HTA coils
Figure 5 — MN and magnetic field-generating coils
Capacitors C1 and C2 shall be adjusted (e.g. parallel capacitors) to match the resistor, RHTA, and HTA1 and
HTA2 to 50 Ω of the amplifier output. Values for C1, C2 and RHTA shall be adjusted around the
...