IEC TS 62998-3:2023

IEC TS 62998-3 ®
Edition 1.0 2023-08
TECHNICAL
SPECIFICATION
Safety of machinery – Safety-related sensors used for the protection of
persons –
Part 3: Sensor technologies and algorithms

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IEC TS 62998-3 ®
Edition 1.0 2023-08
TECHNICAL
SPECIFICATION
Safety of machinery – Safety-related sensors used for the protection of

persons –
Part 3: Sensor technologies and algorithms

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.110; 21.020 ISBN 978-2-8322-7174-2

– 2 – IEC TS 62998-3:2023 © IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Sensor technologies . 11
4.1 General considerations . 11
4.2 SRS using visible light . 13
4.2.1 General . 13
4.2.2 Material considerations . 13
4.2.3 Measurement method considerations . 13
4.2.4 Sensing unit arrangement considerations . 14
4.3 SRS using near infrared radiation . 17
4.3.1 General . 17
4.3.2 Material considerations . 17
4.3.3 Measurement method considerations . 18
4.3.4 Sensing unit arrangement considerations . 18
4.4 SRS using middle infrared radiation . 19
4.4.1 General . 19
4.4.2 Material considerations . 20
4.4.3 Measurement method considerations . 20
4.4.4 Sensing unit arrangement considerations . 20
4.5 SRS using millimetre wave radiation . 21
4.5.1 General . 21
4.5.2 Material considerations . 21
4.5.3 Measurement method considerations . 21
4.5.4 Sensing unit arrangement considerations . 22
4.6 SRS using radio/millimetre wave radiation . 23
4.6.1 General . 23
4.6.2 Tag considerations . 23
4.6.3 Measurement method considerations . 23
4.6.4 Sensing unit arrangement considerations . 24
4.7 SRS using ultrasound wave radiation . 25
4.7.1 General . 25
4.7.2 Material considerations . 25
4.7.3 Measurement method considerations . 25
4.7.4 Sensing unit arrangement considerations . 26
5 Algorithm related considerations . 27
5.1 General . 27
5.2 Design and development phase . 30
5.2.1 General . 30
5.2.2 Achieve the detection of objects . 32
5.2.3 Improve the dependability of the detection capability . 33
5.2.4 Provide confidence information at the output unit . 33
5.3 Integration and installation phase . 33
5.3.1 General . 33

5.3.2 Achieve improved detection of objects . 35
5.3.3 Improve the dependability of the detection capability . 36
5.3.4 Provide confidence information at the output unit . 36
5.4 Maintenance phase . 36
Annex A (informative) Physical property reflectivity for visible light or near infrared
radiation . 38
A.1 Process in accordance with IEC TS 62998-1 . 38
A.2 Persons or parts of a person . 39
Annex B (informative) Physical property reflectivity for millimetre wave radiation . 42
Annex C (informative) Physical property temperature for middle infrared radiation . 44
C.1 Process in accordance with IEC TS 62998-1 . 44
C.2 Exemplary determination of the temperature . 45
Annex D (informative) Physical property reflectivity for ultrasound wave radiation . 47
Bibliography . 50

Figure 1 – Co-located and stationary sensing unit arrangement . 15
Figure 2 – Separated and stationary sensing unit arrangement . 15
Figure 3 – Multiple and stationary sensing unit arrangement . 16
Figure 4 – Co-located and moving sensing unit arrangement . 16
Figure 5 – Separated and moving sensing unit arrangement . 16
Figure 6 – Multiple and moving sensing unit arrangement . 16
Figure 7 – Exemplary combined stationary and moving sensing unit arrangement. 17
Figure 8 – Exemplary multiple combined and moving sensing unit arrangement . 17
Figure 9 – Algorithms exemplary applied to an SRS or an SRSS . 28
Figure 10 – Flowchart for algorithm based on requirements . 29
Figure 11 – Flowchart for algorithm based on training data . 30
Figure 12 – Exemplary use of algorithm for peak extraction . 31
Figure 13 – Exemplary use of algorithm to combine measurement information . 32
Figure 14 – Exemplary combination of two SRS in an SRSS . 34
Figure 15 – Exemplary integration of SRS measurement information in an SRSS . 35
Figure C.1 – Illustration of temperature measurement . 46
Figure D.1 – Object ultrasonic reflectivity quantified by acoustic impedance or
reflection coefficient . 47
Figure D.2 – Object ultrasonic reflectivity quantified by radar cross section . 48

Table 1 – Specific sensor types used as part of SRS . 12
Table A.1 – Range of diffuse reflectance values of human skin if detection of skin can
be derived from the intended use . 39
Table A.2 – Range of diffuse reflectance values of clothes if detection of parts of
persons can be derived from the intended use . 40
Table A.3 – Diffuse reflectance values if detection of the whole body of persons can be
derived from the intended use . 41

– 4 – IEC TS 62998-3:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF MACHINERY – SAFETY-RELATED SENSORS
USED FOR THE PROTECTION OF PERSONS

Part 3: Sensor technologies and algorithms

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 62998-3 has been prepared by IEC technical committee TC 44: Safety of machinery –
Electrotechnical aspects. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
44/981/DTS 44/1002/RVDTS
Full information on the voting for the approval of this Technical Specification 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/standardsdev/publications.
This document is intended to be used in conjunction with IEC TS 62998-1.
A list of all parts in the IEC 62998 series, published under the general title Safety of machinery
– safety-related sensors used for the protection of persons, can be found on the IEC website.
Future documents in this series will carry the new general title as cited above. Titles of existing
documents in this series will be updated at the time of the next edition.
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,
• replaced by a revised edition, or
• amended.
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 TS 62998-3:2023 © IEC 2023
INTRODUCTION
Applications of automated guided vehicles, service robotics used in public areas or human
machine interaction in industries show an increasing demand and use of new sensor
technologies and new kinds of sensor functions with respect to hazard exposure of persons. A
rapidly increasing number of sensors, with different sensor technologies, are used in these
applications to achieve a high degree of automation up to autonomy. The systematic capabilities
of such sensors are relevant to reduce the risk of personal injury. Other aspects of functional
safety related to sensors as part of control systems are covered by e.g. IEC 61508 (all parts),
IEC 62061 or ISO 13849 (all parts).
Existing design specific sensor standards set requirements on systematic capabilities for a
selected sensor technology and how these can be assessed by analysis and test. The specific
requirements are derived from products with limited classes of safety performance and already
well-known sensor technology.
IEC TS 62998-1 sets general requirements for the development, integration and maintenance
of safety related sensors (SRS) and safety related sensor systems (SRSS) applicable to all
sensor technologies with special attention to systematic capabilities. IEC TS 62998-1 is
appropriate for the risk reduction in accordance with all classes of safety performance in an
identified application.
First assessments of SRS/SRSS in accordance with IEC TS 62998-1 identified the need for
additional guidance for the required analysis of sensor technologies and use of algorithms.
Sensor technology is defined by the wavelength range, the measurement method and the
arrangement of the sensing unit in an SRS, respectively arrangement of SRS in an SRSS. This
document gives guidance for sensor technologies without setting requirements for a specific
design or limiting the class of safety performance. If applicable to the sensor technology,
additional information is given for physical properties of the objects to be detected or relevant
objects that interfere with the detection of such objects.
Algorithms are a core element to achieve safety related functions in an SRS/SRSS, such as
signal processing to extract peaks in analogue signals, localization or classification of objects
that are important to guide an autonomous or highly automated system in a more or less known
surrounding. Platforms such as cloud services provide e.g. algorithms or measures for their
automated generation that can be implemented by different integrators of SRS into an SRSS or
by the manufacturer of such sensors. This document gives guidance on the correct
implementation of algorithms to prevent intolerable risk for persons.

SAFETY OF MACHINERY – SAFETY-RELATED SENSORS
USED FOR THE PROTECTION OF PERSONS

Part 3: Sensor technologies and algorithms

1 Scope
This part of IEC 62998, which is a technical specification, gives guidance on:
– analysis of sensor technologies of different wavelength ranges, measurement methods, and
the sensing unit arrangement in an SRS, respectively the arrangement of SRSs in an SRSS;
– representative physical properties of safety-related objects with due consideration of their
material characteristics and the sensor technology/technologies used in an SRS/SRSS to
achieve the detection capability and comparable results during verification and validation;
– analysis of the interference of objects present in the surrounding on the safety related
objects and thereby the influence on the dependability of the detection capability;
– use of algorithms during design, development and maintenance to achieve appropriate
detection capability and dependability of detection;
– appropriate use of algorithms during the integration of SRS or SRSS by the integrator to
improve execution of measurement information or provide decision information derived from
measurement information.
If an SRS/SRSS uses sensor technologies not stated in this document, then the generic
approach in accordance with IEC TS 62998-1 applies.
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 60079-29 (all parts), Explosive atmospheres - Part 29 - Gas detectors
IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-
related systems
IEC TS 62998-1:2019, Safety of machinery - Safety-related sensors used for the protection of
persons
EN 50402, Electrical apparatus for the detection and measurement of combustible or toxic
gases or vapours or of oxygen – Requirements on the functional safety of fixed gas detection
systems
– 8 – IEC TS 62998-3:2023 © IEC 2023
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 http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
acoustic impedance
at a specified surface, quotient of sound pressure by volume velocity through the surface
[SOURCE: IEC 60050-801:1994 [3] , 801-25-40]
3.2
algorithm
finite set of well-defined rules for the solution of a problem in a finite number of steps
Note 1 to entry: An algorithm can be implemented by software or hardware means or by a combination of both.
[SOURCE: IEC 60050-171:2019 [2], 171-05-07, modified – Note to entry has been added]
3.3
bidirectional reflectance distribution function
function describing how a wave is reflected at a surface of an object
Note 1 to entry: It is employed in the optics of real-world light, in computer graphics algorithms, and in computer
vision algorithms.
Note 2 to entry: It is usually applied in case of a mixed reflection.
3.4
cloud service
one or more capabilities offered via cloud computing invoked using a defined interface
[SOURCE: ISO/IEC 20924:2021 [12], 3.1.8]
3.5
concentration
amount of the gas or vapour of interest in a specified amount of the background gas or air
Note 1 to entry: Typical units include volume fraction (V/V); molar (moles per mole – m/m); percentage of the LFL
of a particular substance; parts per million by volume (ppm); and parts per billion by volume (ppb).
3.6
depth from focus/defocus
changing of focal setting parameters to estimate distances in a scene
Note 1 to entry: Usually the distances are related to an observed surface of that scene.
Note 2 to entry: The distances are reconstructed from a set of two or more images related to the changed focal
parameters of the observing sensor (e.g. light field cameras)
___________
Numbers in square brackets refer to the bibliography.

3.7
diffuse reflectance value
ratio of the diffusely reflected part of a wave and the incoming wave
Note 1 to entry: An ideal diffuse reflecting surface is said to exhibit Lambertian characteristic, meaning that there
is equal luminance when viewed from all directions lying in the half-space adjacent to the surface.
3.8
diffuse reflection
scattering by reflection in which, on the macroscopic scale, there is no regular reflection
[SOURCE: IEC 60050-845:2020 [4], 845-24-054, modified – Note to entry has been removed]
3.9
direct time-of-flight
when a pulse is emitted, time difference between outgoing and incoming signals measured as
an equivalent of time-of-flight
Note 1 to entry: For the use in an SRS/SRSS, the wavelength range for near infrared radiation is defined between
50 µm and 1 mm.
3.10
illuminated portion
effective echoing area of an object in terms of radar cross section
3.11
indirect time-of-flight
when a continuous amplitude modulated signal is emitted, phase difference between outgoing
and incoming signals measured as an equivalent of time-of-flight
3.12
level switching
comparison of a detected signal related to a predefined threshold
3.13
machine learning model
mathematical construct that generates an inference, or prediction, based on input data
EXAMPLE If a univariate linear function (y = θ0 + θ1x) has been trained using linear regression, the resulting model
can be y = 3 + 7x.
[SOURCE ISO/IEC 22989:2022 [13], 3.2.11, modified –Note to entry has been removed]
3.14
measurement method
generic description of a logical organization of operations used in a measurement
Note 1 to entry: Measurement methods may be qualified in various ways such as: substitution measurement
method, differential measurement method, and null measurement method; or direct measurement method and indirect
measurement method. See IEC 60050-300 [6].
[SOURCE: ISO/IEC GUIDE 99:2007 [18], 2.5]
3.15
middle infrared radiation
part of the infrared spectrum of optical radiation in which the wavelengths are longer than those
of near infrared radiation and shorter than those of long infrared radiation
Note 1 to entry: For the use in an SRS/SRSS, the wavelength range for middle infrared radiation is defined between
3 µm and 50 µm.
– 10 – IEC TS 62998-3:2023 © IEC 2023
3.16
mixed reflection
partly regular and partly diffuse reflection
[SOURCE: IEC 60050-845:2020 [4], 845-24-056]
3.17
near infrared radiation
part of the infrared spectrum of optical radiation in which the wavelengths are longer than those
of visible radiation and shorter than those of middle infrared radiation
Note 1 to entry: For the use in an SRS/SRSS, the wavelength range for near infrared radiation is defined between
780 nm and 3 µm.
3.18
passive infrared sensor
sensor that is used to detect temperature changes
Note 1 to entry: Unlike other temperature sensors (e.g. thermography cameras), passive infrared sensors do not
respond to a specific temperature level that is constant over time, but only to the change in temperature.
Note 2 to entry: Passive infrared sensors are based on pyroelectricity, a property of some piezoelectric
semiconductor crystals.
3.19
practical use
use that involves real situations and events, rather than just ideas, theories or generally
understood patterns of usage
EXAMPLE Derivation of real situations, events and scenarios from the application of the SRS/SRSS in the end user
environment.
Note 1 to entry: The practical use can be a subset or an expansion of the intended use.
3.20
radar cross section
RCS
equivalent echoing area which is 4 π times the ratio of the power per unit solid angle scattered
in a specified direction to the power per unit area in a plane wave incident on the scatterer from
a specified direction
Note 1 to entry: The concept of RCS is also applied in case of ultrasound wave radiation.
[SOURCE: ISO 8729-2:2009 [19], 3.3, modified – the Note 1 to entry has been added]
3.21
reflectivity
the ability of an object to reflect a wave
EXAMPLE A wave can be of electromagnetic or acoustic type.
3.22
reflection coefficient
ratio of the regular reflected part of a wave and the incident wave
3.23
regular reflection
specular reflection
reflection in accordance with the laws of geometrical optics, without scattering
[SOURCE: IEC 60050-845:2020 [4], 845-24-052]

3.24
tag
human- or machine-readable mark, or digital identity used to communicate information about
an entity
Note 1 to entry: A tag can contain information that can be read by sensors to aid in identification of the physical
entity.
[SOURCE: ISO/IEC 20924:2018 [12], 3.1.31]
3.25
thermography camera
an imaging method for displaying the surface temperature of objects
Note 1 to entry: The intensity of the infrared radiation emitted by a point is interpreted as a measure of its
temperature.
Note 2 to entry: In this document, thermography is applied to passive techniques that do not require active energy
emitted by the SRS.
3.26
training data
subset of input data samples used to train a machine learning model
[SOURCE: ISO/IEC 22989:2022 [13], 3.2.22]
4 Sensor technologies
4.1 General considerations
An SRS uses sensor technologies for the detection of safety related objects (persons and
hazardous objects) and automation related objects. Objects present in the surrounding can
interfere with the safety related object and thereby affect the dependability of the detection
capability.
In accordance with 5.3 of IEC TS 62998-1:2019, the type and combination of physical properties
of the safety related object with due consideration of the sensor technology/technologies shall
be analysed.
During the analysis of the sensor technology of an SRS the manufacturer shall take into
consideration:
– wavelength range;
– measurement method; and
– sensing unit(s) arrangement.
In Table 1, examples of well-known sensor types are listed to support the specification of the
sensor technology.
NOTE 1 Within an SRS, one or more types of sensors, wavelength or measurement methods can be used.

– 12 – IEC TS 62998-3:2023 © IEC 2023
Table 1 – Specific sensor types used as part of SRS
Examples of sensor Wave type Wavelength Frequency range Measurement method
types range
– Ultrasound Sound wave 11 µm – 21 mm 16 kHz – 30 MHz – Pulse-wave,
(normal – Continuous wave,
atmosphere)
– Frequency modulated
continuous wave (FMCW)
– Ultra-wideband Radio / 22 mm – 125 kHz – – Presence detection or
(UWB), Millimetre 2400 m 13,56 GHz localization of a tag, for
wave details see 4.6.3
– Radio frequency
Identification
(RFID),
– Wireless local
area network,
– Wireless personal
area network,
– 5G
– Radar Millimetre 2 mm – 33 mm 9 GHz – – In-range distance,
wave 148,5 GHz
– Doppler,
– Angle of arrival,
– Passive infrared Middle 3 µm – 50 µm 6 THz – 100 THz – Level switching,
sensor, infrared
– See normative references
– Thermography in 4.4 for infrared gas
camera, detector.
– Infrared gas
detector
– Lidar,
Near infrared 780 nm – 3 µm 100 THz – – Direct time-of-flight,
384 THz
– Stereoscopic – Indirect time-of-flight,
Camera,
– Triangulation,
– Time-of-flight
– Level switching,
camera,
– FMCW,
– Light field camera,
– Depth from focus / defocus
– Lightgrid,
– Light beam device
– Lidar, Visible 380 nm – 384 THz – – Direct time-of-flight,
780 nm 789 THz
– Stereoscopic – Indirect time-of-flight,
Camera,
– Triangulation,
– Time-of-flight
– Level switching
camera
– Depth from focus /
– Light field camera,
defocus.
– Lightgrid,
– Light beam device
NOTE 2 Wavelength depends on media and media properties.
NOTE 3 Wavelength ranges can change due to technological improvements or revised regulatory constraints.
The considered wavelength range, measurement method and sensing unit arrangement shall
be used for the identification of relevant physical properties of objects and their limits:
– to perform the person detection function within the safety-related zone if applicable;
– to perform the hazardous object function within the safety-related zone if applicable;

– inside the safety-related zone that influences the person detection function or the hazardous
object function if applicable;
– outside the safety-related zone but inside the sensing zone that influences the person
detection function or the hazardous object function if applicable.
The relevant physical properties and their limits shall be used for analysis, test, or both, of the
detection capability and the dependability of the detection capability as stated in 5.8.1 of
IEC TS 62998-1:2019.
The objects, their relevant physical properties and their limits:
– shall be derived from the intended use by the manufacturer during design and development
as far as reasonably practical; or
– shall be identified in the application by the integrator or end user during integration or
installation phase in accordance with procedures provided by the manufacturer, and
– shall not reduce the detection capability and the dependability of the detection capability
below the limits as provided in the information for use.
Depending on the specified wavelength range used in an SRS one or more of the following
subclauses of Clause 4 shall be considered in addition to the physical properties and their limits
given in 5.8.2 of IEC TS 62998-1:2019.
NOTE 4 This includes the identification of relevant physical properties and their limits for objects with active
characteristics such as tags in accordance with 4.6.
NOTE 5 It is reminded that environmental influences (e.g. pollution) that are relevant for the dependability of the
detection capability are given in IEC TS 62998-1:2019, 5.8.3.
4.2 SRS using visible light
4.2.1 General
If the SRS is using visible light, at least the following object-related physical properties shall be
considered:
– geometry and location (see IEC TS 62998-1:2019 ,5.8.2.2);
– velocity and acceleration (see IEC TS 62998-1:2019 ,5.8.2.2);
– material characteristics (see 4.2.2).
The object-related physical properties shall be used for analysis, test, or both, of the detection
capability and the dependability of the detection capability. The physical properties may be
used, independently or in combination, in testing or analysis. (see Annex A).
4.2.2 Material considerations
The material of the safety related object is relevant to characterize the interaction of visible light
with the object. The interaction in a certain direction is determined by the electromagnetic
properties which themselves depend on wavelength, polarization, field strength and angle of
incidence. To quantify the interaction the reflectivity of the safety-related object shall be used
(see Annex A).
4.2.3 Measurement method considerations
Depending on the measurement method, the following effects shall be considered for the
analysis, test, or both, of the detection capability and the dependability of the detection
capability:
a) direct time-of-flight:
1) multipath effects of objects interfering within the sensing zone.

– 14 – IEC TS 62998-3:2023 © IEC 2023
b) indirect time-of-flight:
1) multipath effects of objects interfering within the sensing zone.
2) non-ambiguity range related to object location within the sensing zone;
c) triangulation:
1) influence of periodic structure;
2) effects of low contrast.
d) level switching:
1) effects increasing or reducing the signal.
e) depth from focus/defocus:
1) effects of low contrast;
2) limited sensing zone due to small apertures.
NOTE Small apertures are relevant for monocular cameras using micro lenses.
4.2.4 Sensing unit arrangement considerations
Depending on the sensing unit arrangement, the following object and sensing unit related
effects shall be considered for the analysis, test, or both, of the detection capability and the
dependability of the detection capability:
a) co-located and stationary (e.g. emitter and receiver in a sensing unit are in close proximity
and the sensing unit is in a fixed location, see Figure 1):
1) obscuration of objects in a line within the safety-related zone.
b) separated and stationary (e.g. emitter and receiver in a sensing unit are separated and the
sensing unit is in a fixed location, see Figure 2):
1) obscuration of objects anywhere in the safety-related zone;
2) directional characteristic of non-ideal diffuse radiators.
c) multiple and stationary (e.g. more than one sensing unit separated from each other with the
sensing units being in a fixed location, see Figure 3):
1) obscuration of objects anywhere in the safety-related zone;
2) directional characteristic of non-ideal diffuse radiators;
3) similarity of object related physical properties from different perspectives;
4) interference of sensing units of identical design.
d) co-located and moving (e.g. emitter and receiver in a sensing unit are in close proximity and
the sensing unit is moving, see Figure 4):
1) obscuration of objects in a line within the safety-related zone;
2) physical properties of the object can change with the location of the sensing unit;
3) velocity of the sensing unit.
e) separated and moving (e.g. emitter and receiver in a sensing unit are separated and the
sensing unit is moving, see Figure 5):
1) obscuration of objects anywhere in the safety-related zone;
2) directional characteristic of non-ideal diffuse radiators;
3) physical properties of the object can change with the location of the sensing unit;
4) velocity of the sensing unit.

f) multiple and moving (e.g. more than one sensing unit separated from each other and the
sensing units are moving, see Figure 6):
1) obscuration of objects anywhere in the safety-related zone;
2) directional characteristic of non-ideal diffuse radiators;
3) similarity of object related physical properties from different perspectives;
4) physical properties of the object can change with the locations of the sensing units;
5) velocity of the sensing units;
6) interference of sensing units of identical design.
g) combined stationary and moving (e.g. combination of stationary and moving sensing units
separated from each other, see Figure 7):
1) obscuration of objects anywhere in the safety-related zone;
2) directional characteristic of non-ideal diffuse radiators;
3) similarity of object related physical properties from different perspectives;
4) physical properties of the object can change with the locations of the sensing units;
5) velocity of the sensing units;
6) interference of sensing units of identical design.
h) multiple combined and moving (e.g. combination of sensing units separated from each other
and the sensing units are moving independently to each other, see Figure 8):
1) obscuration of objects anywhere in the safety-related zone;
2) directional characteristic of non-ideal diffuse radiators;
3) similarity of object related physical properties from different perspectives;
4) physical properties of the object can change with the locations of the sensing units;
5) velocity of the sensing units;
6) interference of sensing units of identical design.

Key
E emitter
R receiver
SU stationary sensing unit
Figure 1 – Co-located and stationary sensing unit arrangement

Key
E emitter
R receiver
SU stationary sensing unit
Figure 2 – Separated and stationary sensing unit arrangement

– 16 – IEC TS 62998-3:2023 © IEC 2023

Key
SU 1 stationary sensing unit 1
SU 2 stationary sensing unit 2
Figure 3 – Multiple and stationary sensing unit arrangement

Key
E emitter
R receiver
SU moving sensing unit
Figure 4 – Co-located and moving sensing unit arrangement

Key
E emitter
R receiver
SU moving sensing unit
Figure 5 – Separated and moving sensing unit arrangement

Key
SU 1 moving sensing unit 1
SU 2 moving sensing unit 2
Figure 6 – Multiple and moving sensing unit arrangement

Key
SU 1 moving sensing unit 1
SU 2 moving sensing unit 2
SU 3 stationary sensing unit 3
SU 4 stationary sensing unit 4
Figure 7 – Exemplary combined stationary and moving sensing unit arrangement

Key
SU 1 moving sensing unit 1
SU 2 moving sensing unit 2
Figure 8 – Exemplary multiple combined and moving sensing unit arrangement
4.3 SRS using near infrared radiation
4.3.1 General
If the SRS is using near infrared radiation, at least the following object-related physical
properties shall be considered:
– geometry and location (see IEC TS 62998-1:2019, 5.8.2.2);
– velocity and acceleration (see IEC TS 62998-1:2019, 5.8.2.2);
– material characteristics.
The object-related physical properties shall be used for analysis, test, or both, of the detection
capability and the dependability of the detection capability. The physical properties may be
used, independently or in combination, in testing or analysis. (see Annex A).
4.3.2 Material considerations
The material of the safety related object is relevant to characterize the interaction of near
infrared radiation with the object. The interaction is determined by the electromagnetic
properties which themselves depend on wavelength, polarization, field strength and angle of
incidence. To quantify the interaction the reflectivity of the safety-related object shall be used
(see Annex A).
If the physical property temperature is the determining material characteristic of the safety-
related object for the detection in the near infrared wavelength range, then 4.4 shall be applied
instead of 4.3.
– 18 – IEC TS 62998-3:2023 © IEC 2023
4.3.3 Measurement method considerations
Depending on the measurement method, following effects shall be considered for the analysis,
test, or both, of the detection capability and the dependability of the detection capability:
a) direct time-of-flight:
1) multipath effects of objects interfering within the sensing zone.
b) indirect time-of-flight:
1) multipath effects of objects interfering within the sensing zone;
2) non-ambiguity range related to object location within the sensing zone.
c) triang
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