IEC 62908-12-10:2017

IEC 62908-12-10 ®
Edition 1.0 2017-06
INTERNATIONAL
STANDARD
colour
inside
Touch and interactive displays –
Part 12-10: Measurement methods of touch displays – Touch and electrical
performance
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IEC 62908-12-10 ®
Edition 1.0 2017-06
INTERNATIONAL
STANDARD
colour
inside
Touch and interactive displays –

Part 12-10: Measurement methods of touch displays – Touch and electrical

performance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120 ISBN 978-2-8322-4394-7

– 2 – IEC 62908-12-10:2017  IEC 2017
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Measuring conditions . 7
4.1 Standard measuring environmental conditions . 7
4.2 Standard atmospheric conditions for reference measurements and tests . 8
4.3 Standard positioning equipment and setup . 8
4.4 Human operator alternative to standard positioning equipment . 9
4.5 Test bar size, shape and material parameters . 10
5 Touch performance measuring methods . 11
5.1 General . 11
5.2 Accuracy test . 11
5.2.1 Purpose . 11
5.2.2 Test procedure . 11
5.2.3 Report . 15
5.3 Repeatability/jitter test . 15
5.3.1 Purpose . 15
5.3.2 Test procedure . 15
5.3.3 Report . 17
5.4 Linearity test . 18
5.4.1 Purpose . 18
5.4.2 Test procedure . 18
5.4.3 Report . 20
5.5 Reproducibility test . 20
5.5.1 Purpose . 20
5.5.2 Test procedure . 21
5.5.3 Report . 22
5.6 Signal-to-noise ratio (SNR) test . 23
5.6.1 Purpose . 23
5.6.2 Test procedure . 24
5.6.3 Report . 25
5.7 Report rate test . 25
5.7.1 Purpose . 25
5.7.2 Test procedure . 25
5.7.3 Report . 26
5.8 Latency test . 26
5.8.1 Purpose . 26
5.8.2 Test procedure . 26
5.8.3 Report . 27
5.9 Electrical noise immunity test . 27
5.9.1 Purpose . 27
5.9.2 Test procedure . 27
5.9.3 Report . 28
5.10 Water droplet immunity test . 28
5.10.1 Purpose . 28
5.10.2 Test procedure . 29

5.10.3 Report . 29
5.11 Optical noise immunity test . 29
5.11.1 Purpose . 29
5.11.2 Test procedure . 30
5.11.3 Report . 30
5.12 Power consumption test . 30
5.12.1 Purpose . 30
5.12.2 Test procedure . 30
5.12.3 Report . 30
5.13 Perpendicular touch/hover distance test . 30
5.13.1 Purpose . 30
5.13.2 Test procedure . 30
5.13.3 Report . 31
Annex A (informative) Electrical performance measuring methods of touch sensor . 32
A.1 Resistance . 32
A.1.1 General . 32
A.1.2 Test samples . 32
A.1.3 Measurement equipment . 32
A.1.4 Procedures . 32
A.1.5 Data analysis . 33
A.1.6 Report . 33
A.2 Trans-capacitance . 33
A.2.1 General . 33
A.2.2 Test samples . 33
A.2.3 Measurement equipment . 33
A.2.4 Procedure . 33
A.2.5 Data analysis . 34
A.2.6 Report . 34

Figure 1 – Composition of test equipment . 9
Figure 2 – Concept of performance measurement . 9
Figure 3 – Example of manual test tool (left), positioning without triggering a touch
event (middle) and recording a touch event (right) . 10
Figure 4 – Examples of test bars . 10
Figure 5 – Location of edge area and centre area . 12
Figure 6 – Point grid . 12
Figure 7 – Accuracy definition . 13
Figure 8 – Example of measurement result and calculation of accuracy . 15
Figure 9 – Repeatability in touch sensor module . 16
Figure 10 – Example of measurement result for repeatability . 17
Figure 11 – Dragging line for linearity test . 18
Figure 12 – Linearity definition . 19
Figure 13 – Example of measurement and calculation of linearity . 20
Figure 14 – Example of reproducibility test results . 21
Figure 15 – Reproducibility test procedure . 22
Figure 16 – Examples of measurements of reproducibility – Velocity dependence . 23
Figure 17 – SNR definition concept . 24

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Figure 18 – Dragging direction for reporting time measurement . 25
Figure 19 – Reporting time interval measurement . 26
Figure 20 – Latency measurement . 26
Figure 21 – Example of the effect of external noise . 27
Figure 22 – External noise injection . 28
Figure 23 – Report of external noise immunity . 28
Figure 24 – Example of water drop effect . 29
Figure 25 – Water droplet test procedure . 29
Figure 26 – Perpendicular touch/hover distance measurement . 31
Figure A.1 – Diagrammatic representation of measurement of resistance . 33
Figure A.2 – Diagrammatic representation of measurement of capacitance . 34

Table 1 – Standard conditions for reference measurements and tests . 8
Table A.1 – Specification of LCR impedance meter . 32

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TOUCH AND INTERACTIVE DISPLAYS –

Part 12-10: Measurement methods of touch displays –
Touch and electrical performance

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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.
International Standard IEC 62908-12-10 has been prepared by IEC technical committee 110:
Electronic display devices.
The text of this International Standard is based on the following documents:
FDIS Report on voting
110/861/FDIS 110/872/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC 62908-12-10:2017  IEC 2017
A list of all parts in the IEC 62908 series, published under the general title Touch and
interactive displays, 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 "http://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.
A bilingual version of this publication may be issued at a later date.
The contents of the corrigendum of Novembre 2018 have been included in this copy.

IMPORTANT – The 'colour inside' logo on the cover page of this publication 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.
TOUCH AND INTERACTIVE DISPLAYS –

Part 12-10: Measurement methods of touch displays –
Touch and electrical performance

1 Scope
This part of IEC 62908 specifies the standard measuring conditions and methods for
determining touch performance of a touch sensor module. This document is applicable to
touch sensor modules, where the structural relationship between touch sensor, touch
controller, touch sensor module, display panel, touch display panel, and touch display module
is defined in IEC 62908-1-2.
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 60068-1, Environmental testing – Part 1: General and guidance
IEC 62908-1-2 , Touch and interactive displays – Part 1-2: Generic – Terminology and letter
symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60068-1 and
IEC 62908-1-2 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
4 Measuring conditions
4.1 Standard measuring environmental conditions
Measurements shall be carried out under the standard environmental conditions:
• temperature: 25 °C ± 3 °C,
• relative humidity: 25 % RH to 85 % RH,
• atmospheric pressure: 86 kPa to 106 kPa.
When different environmental conditions are used, they shall be noted in the measurement
report.
___________
Under preparation. Stage at the time of publication: IEC/AFDIS 62908-1-2:2017.

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4.2 Standard atmospheric conditions for reference measurements and tests
If the parameters to be measured depend on temperature, pressure and humidity and their
dependence on temperature, pressure and humidity is unknown, the atmospheres to be
specified shall be selected from the following values, as shown in Table 1. The selected
values shall be noted in the relevant specifications.
Table 1 – Standard conditions for reference measurements and tests
a a, b a
Temperature Relative humidity Air pressure
°C % RH kPa
45 to 75 86 to 106
20, 25, 30, and 35 ± 3
a
Including extreme values.
b 3
Absolute humidity ≤ 22 g/m .
4.3 Standard positioning equipment and setup
Standard positioning equipment for touch performance shall be the positioning machine
equipped with a test bar, a moving arm, and a stage onto which the touch sensor module is
placed, as shown in Figure 1. The positioning machine shall move its arm and stage to place
the test bar on the touch sensor module.
There are three types of positions associated with a given test: target, actual and reported
positions. The target position is a desired measurement location in physical space referenced
to a fixed datum on the touch sensor module surface. The actual position is the actual
location of contact during test, referenced to the same fixed datum, which may differ from the
target position due to test bar placement error. The reported position is the location reported
by the touch controller.
As shown in Figure 2, the reported positions from the touch controller are analysed to define
performance measures with respect to the target positions.
The touch sensor module and the stage shall be aligned correctly while setting up the
measurement equipment, because a misalignment between them may introduce coordinate
shifts or rotation between the actual touch positions and target positions; each positioning
machine has its inherent accuracy, which means that an actual touched position does not
coincide with its target position. The performance measurements based on target positions
may include errors due to the accuracy of the positioning machine. The touch sensor module
under test shall be attached to the stage and connected to the electrical interface. The test
bar of the selected diameter shall be attached to the moving arm.

Moving arm
Test bar
Touch sensor
module
Stage
Electrical
interface
IEC
Figure 1 – Composition of test equipment
Positioning machine
Moving arm
Target
(Moving)
position
Stage
Test bar
Touch sensor module
Reported
Performance
position
Actual touched
measure calculation
position
Touch sensor
IEC
Figure 2 – Concept of performance measurement
4.4 Human operator alternative to standard positioning equipment
Under certain circumstances, for example if the display under test is too large for suitable
positioning equipment to be available, a suitably designed test arm may be manually
positioned to enable completion of a subset of the tests described in this document. In this
situation, the test arm needs to be designed carefully to minimise the reasonable achievable
error between actual and target positions when conducting measurements. An example of
such a test arm may consist of a rod with a sliding tip (Figure 3, left), whose materials are
chosen so that contact between the rod and the display does not trigger a touch event
(Figure 3, middle), whereas contact between the sliding tip and the display does trigger a
touch event (Figure 3, right). Such a test arm may be placed accurately and reliably by the
human operator with the sliding tip away from the display, subsequent to which a
measurement may be made by sliding the tip into contact with the display.
Touch
controller
– 10 – IEC 62908-12-10:2017  IEC 2017
IEC IEC IEC
Figure 3 – Example of manual test tool (left), positioning without triggering
a touch event (middle) and recording a touch event (right)
4.5 Test bar size, shape and material parameters
The parameters of the test bar shall be size, shape, and material. Examples of suitable sizes
and shapes of the test bar are shown in Figure 4. Care shall be taken to ensure that material
parameters for the test bar are appropriately chosen given the device category under test.
When the touch sensor module is a capacitive touch system, the test bar shall be electrically
conductive and shall additionally be grounded in order to avoid potential performance
degradation due to electrical noise, unless otherwise stated. A test bar may have an
insulating layer on the base to model the effect of a gloved finger.
For reflection-based optical systems, the reflectivity of the contact end of the test bar shall be
chosen to be spectrally representative of human skin.
In all cases, the appropriate properties (including size, shape and material) of the test bar
shall be reported.
Material: Brass
or
Conductive polyamide resin
Physical property
2 4
Electrical resistivity: < 10 to 10 Ω · cm
Hardness: > R119
Half-sphere type
Cylinder type
ø1,6
ø8 ø10
ø4 ø6
IEC
NOTE ø (test bar diameter) = 4 mm, 6 mm, 7 mm, 9 mm, or 12 mm.
Figure 4 – Examples of test bars

5 Touch performance measuring methods
5.1 General
Fundamental touch performance measuring methods are described in this clause. They shall
be taken into account during characterisation of a touch sensor module to realize a good user
experience.
5.2 Accuracy test
5.2.1 Purpose
The purpose of this test is to measure the ability of touch sensors and modules to indicate
how close touch positions are reported relative to their target positions.
5.2.2 Test procedure
5.2.2.1 General
For the accuracy measurement, one of the following two methods can be selected. The first
method is a straightforward method to evaluate the distance between each target point and its
corresponding reported point. The second method is an indirect method where target grid
points are estimated from reported points. This method can tolerate coordinate shifts which
are caused by a misalignment between the touch sensor module and the stage while setting
up the measurement equipment.
5.2.2.2 Method 1
The active area is defined as the area where touch is recognized. The centre area is defined
as the rest of the active area without the edge area as shown in Figure 5. The edge area is
defined as an area with the width of W from the edge of the active area. The origin and axis
direction shall be defined.
The touch sensor module under test shall be attached to the stage and connected to the
electrical interface.
...