IEC 63522-6:2025

IEC 63522-6 ®
Edition 1.0 2025-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical relays – Tests and measurements –
Part 6: Contact-circuit resistance or voltage drop

Relais électriques – Essais et mesurages –
Partie 6: Résistance (ou chute de tension) du circuit de contact
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IEC 63522-6 ®
Edition 1.0 2025-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical relays – Tests and measurements –

Part 6: Contact-circuit resistance or voltage drop

Relais électriques – Essais et mesurages –

Partie 6: Résistance (ou chute de tension) du circuit de contact

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.120.70  ISBN 978-2-8327-0230-7

– 2 – IEC 63522-6:2025 © IEC 2025
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 5
4 Test procedure . 6
4.1 Elementary relays . 6
4.1.1 Purpose . 6
4.1.2 Procedure . 6
4.1.3 Conditions to be specified . 8
4.2 Reed switches . 8
4.2.1 Purpose . 8
4.2.2 Procedure . 8
4.2.3 Conditions to be specified . 11
5 Evaluation . 11
5.1 General . 11
5.1.1 Elementary relays . 11
5.1.2 Reed switches . 12
5.2 Test report . 12
Bibliography . 14

Figure 1 – Example of a contact-circuit . 6
Figure 2 – Time definitions . 10
Figure 3 – Sequence of contact-circuit resistance measurement . 11

Table 1 – Test current and voltage . 7

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL RELAYS – TESTS AND MEASUREMENTS –

Part 6: Contact-circuit resistance or voltage drop

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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shall not be held responsible for identifying any or all such patent rights.
IEC 63522-6 has been prepared by IEC technical committee 94: Electrical relays. It is an
International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
94/1077/FDIS 94/1118/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.

– 4 – IEC 63522-6:2025 © IEC 2025
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 of IEC 63522 series, published under the general title Electrical relays – Tests
and measurements, 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.
ELECTRICAL RELAYS – TESTS AND MEASUREMENTS –

Part 6: Contact-circuit resistance or voltage drop

1 Scope
This part of lEC 63522 is used for testing all kinds of electrical relays and for evaluating their
ability to perform under expected conditions of transportation, storage and all aspects of
operational use.
NOTE Examples for electrical relays in the sense of this document include electromechanical relays, reed relays,
reed contacts, reed switches, solid-state relays, time relays and technology combinations of these.
This document defines a standard test method to measure contact-circuit resistance or voltage
drop.
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 63522-0, Electrical relays – Tests and measurements – Part 0: General and guidance
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 63522-0 and the
following 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
contact-circuit
output circuit containing contact members (see Figure 1)
___________
Under preparation. Stage at the time of publication: IEC CDV 63522-0:2024.

– 6 – IEC 63522-6:2025 © IEC 2025

Key
1 Contact-circuit
2 Contact member
3 Contact point
Figure 1 – Example of a contact-circuit
4 Test procedure
4.1 Elementary relays
4.1.1 Purpose
The contact-circuit resistance (or voltage drop) test is to check that the resistance (or voltage
drop) across a closed contact remains within specified limits.
4.1.2 Procedure
4.1.2.1 Measurement details
The resistance (or voltage drop) shall be measured using a four-terminal bridge, by the
voltmeter-ammeter method, or, particularly for dynamic tests, using automatic monitoring
equipment.
The contact-circuit resistance shall be measured with AC voltage or DC voltage. AC voltage is
preferred, unless otherwise specified.
For AC measurements, the frequency shall be 0,8 kHz to 2 kHz, unless otherwise prescribed.
For DC measurements, the resistance shall be measured with forward and reverse current,
except for the following situations:
a) dynamic testing;
b) measurement in one direction current is permitted, provided they show equivalent test
results;
c) If the load side with polarity, the resistance is measured according to the specified polarity
without changing the polarity.
The type of measurement shall be as required, and be selected from the following:
– static contact-circuit resistance measurement denotes that, for each measurement, the
contacts remain closed for an interval sufficient to allow all transients to decay. Three test
cycles shall be made;
– dynamic contact-circuit resistance measurement denotes that the relay coil is energized by
a square wave, the frequency being as required. A specified number of cycles shall be
made, and each of the cycles shall be monitored. Monitoring shall start after the contact has
reached stable closed condition, or after at least 30 % of the closed part of each cycle has
elapsed, whichever is later. Any irregularity in contact-circuit resistance not exceeding a
duration of 10 μs shall be ignored, unless another value is required by the manufacturer, for
example 100 μs.
The contact shall not be operated while the measuring voltage is applied, unless otherwise
explicitly stated by the manufacturer. The voltage shall be applied after the contacts are closed,
and removed before the contacts are opened.
Where the connection points specified in the detail specification are not directly accessible, the
resistance of the cable or wire used shall be subtracted from the measured value. The corrected
value shall be recorded.
The coil shall be energized at the rated voltage, unless otherwise specified.
There shall be no preconditioning cycle prior to the measurement, unless otherwise explicitly
stated by the manufacturer.
During the measurement, any abnormal pressure on the contacts under test and movement of
the test cables shall be avoided.
NOTE During an endurance test, checking of contact-circuit resistance is carried out by another method, for
example by checking the voltage drop across the tested contact with the load current flowing through the contact, or
any other technical equivalent measurement.
4.1.2.2 Test current and voltage
In order to get the value closer to the actual application, the test current and voltage should
correspond to the actual load conditions.
If the on-line test cannot apply the actual load conditions, the test current and voltage should
be selected according to Table 1 depending on the rated contact current.
Table 1 – Test current and voltage
Rated contact current Maximum test current Maximum test voltage
A A V
<0,01 0,001 0,03
≥0,01~<0,1 0,01 0,03
≥0,1~<1 0,1 10
≥1~<30 1 30
≥30 20 30
___________
The non-repetitive transient value considered as irregularity.

– 8 – IEC 63522-6:2025 © IEC 2025
4.1.2.3 Measuring cycles
4.1.2.3.1 Measurement with direct current (DC)
One measuring cycle consists of:
a) application of the coil voltage;
b) measurement with current flowing in one direction;
c) measurement with current flowing in the opposite direction (not applicable for measurement
in one direction current according to 4.1.2.1);
d) disconnection of the coil voltage.
4.1.2.3.2 Measurement with alternating current (AC)
One measuring cycle consists of:
a) application of the coil voltage;
b) making the measurement;
c) disconnection of the coil voltage.
NOTE Unless otherwise specified, the contact(s) made are not disturbed between the end of the preceding test and
the application of the voltage in this test.
4.1.3 Conditions to be specified
The conditions to be specified are the following:
a) type of measurement (with DC or AC voltage);
b) frequency of the test voltage, if other than 0,8 kHz to 2 kHz (only in case of measurement
with AC voltage);
c) type of measurement: steady-state or dynamic operation;
d) for dynamic tests, the frequency of the square wave, the number of cycles, and the rated
measurement time;
e) coil voltage value, if other than rated value;
f) points of measurement;
g) test contact current;
h) test contact voltage;
i) the number of values for measurement shall be specified in the detailed specification;
j) evaluation in case of multiple values;
k) maximum contact-circuit resistance.
4.2 Reed switches
4.2.1 Purpose
The contact-circuit resistance shall not exceed the value prescribed in the detail specification.
4.2.2 Procedure
The contact-circuit resistance shall be measured by the 4-point (Kelvin) method at a point 6 mm
from the point of emergence of the termination from the seal, or as required in the detail
specification.
The voltage and current applied to the contact-circuit shall not exceed 6 V and 1 A AC RMS or
DC unless otherwise required in the detail specification.

The frequency of the alternating current shall be in the audio frequency range.
The switch shall be saturated magnetically unless otherwise required and the test coil
energization reduced to a value required in the detail specification.
The break-contact-circuit resistance shall be measured without energization of the test coil
unless otherwise specified.
(see Figure 2) as
The measurement circuit can be connected to the switch at instants 0 or t
required in the detail specification.
The measurement circuit shall be disconnected from the switch at the instant t as required in
the detail specification.
The measurement of the contact-circuit resistance shall be made between instant t and t for
2 3
the make contact and between t and t for the break contact, see Figure 3.
5 6
– 10 – IEC 63522-6:2025 © IEC 2025

a) Break-before-make
b) Make-before-break
Energization of the test coil De-energization of the test coil
t : operate break time t : release break time
1 11
t : operate make time t : release make time
2 12
t : operate transfer time t : release transfer time
3 13
t : operate bridging time t : release bridging time
4 14
t and t : bounce times t and t : bounce times
5 6 15 16
V : test supply voltage
B
Figure 2 – Time definitions
Figure 3 – Sequence of contact-circuit resistance measurement
4.2.3 Conditions to be specified
The conditions to be specified are the following:
a) Test coil.
b) Point of measurement, if other than 6 mm.
c) maximum contact-circuit resistance.
d) Value of saturation and the reduced value.
e) t , t , t , t , t and t .
1 2 3 4 5 6
f) Applied measurement voltage and current (if applicable).
g) The frequency of the applied qualities used for contact-circuit resistance test, where
applicable.
5 Evaluation
5.1 General
5.1.1 Elementary relays
The value of the contact-circuit resistance shall not exceed, for any measurement, the value
specified in the detail specification.
For static contact-circuit resistance measurement, the value of the contact-circuit resistance
shall be the mean of all measurement, unless otherwise specified.
For dynamic contact-circuit resistance measurement, the value of the contact-circuit resistance
shall be the mean and standard deviation of each cycle, unless otherwise specified.
When DC measurement for both direction current, the contact-circuit resistance shall be the
average of the two values obtained with forward and reverse current. Using the following
equation will ensure that the calculated resistance is always correct:
VV-
mf mr
R=
II+
fr
– 12 – IEC 63522-6:2025 © IEC 2025
where
R is the resistance;
V is the measured forward voltage;
mf
V is the measured reverse voltage;
mr
I is the forward current;
f
I is the reverse current.
r
NOTE 1 In the equation, the sign of the voltage measurements is included.
NOTE 2 V and V have opposite polarities, one of which is positive and the other is negative.
mf mr
NOTE 3 Any deviation from the standard test procedure is clearly indicated in the test report.
5.1.2 Reed switches
The value of contact-circuit resistance shall be the mean of the two values and shall not exceed,
for any measurement, the value specified in the detail specification.
5.2 Test report
If this part of the IEC 63522 series is executed as a part of a test record of another standard,
then the results shall be reported as required in the other standard.
Otherwise, it is recommended to issue a dedicated test report according to this document.
The test report shall contain all the information necessary to reproduce the test. In particular,
the following shall be recorded:
a) elementary relays:
1) test standard, edition (test procedure);
2) test sample description (unique identification number, drawing, photo, quantity build
status, evaluation of first sample inspection, etc.);
3) sample installation (pictures);
4) the test voltage and current;
5) type of measurement (with DC or AC voltage);
6) frequency of the test voltage, if other than 0,8 kHz to 2 kHz (only in case of measurement
with AC voltage);
7) type of measurement: steady-state or dynamic operation;
8) for dynamic tests, the frequency of the square wave, the number of cycles, and the rated
measurement time;
9) coil voltage value, if other than rated value;
10) points of measurement;
11) number of readi
...