ISO 16549:2021

Textiles — Unevenness of textile strands — Capacitance method

This document describes a method, using capacitance measuring equipment, for determining the unevenness of linear density along the length of textile strands. The method is applicable to tops, slivers, rovings, spun yarns and continuous filament yarns, made from either natural or man-made fibres, in the range of 4 tex (g/km) to 80 ktex (kg/km) for staple-fibre strands and 1 tex(g/km) to 600 tex (g/km) for continuous-filament yarns. It is not applicable to fancy yarns or to strands composed fully or partly of conductive materials such as metals; the latter requires an optical sensor (see A.4), and to raw silk filaments which are tested according to a specific standard. The method describes the preparation of a variance-length curve, as well as the determination of periodicities of linear density. It also covers the counting of imperfections in the yarn, namely of neps and of thick and thin places.

Textiles — Irrégularité des fils textiles — Méthode capacitive

General Information

• Status: Published
• Publication Date: 28-Jan-2021
• ICS: 59.060.01 - Textile fibres in general
• Technical Committee: ISO/TC 38/SC 23 - Fibres and yarns
• Drafting Committee: ISO/TC 38/SC 23 - Fibres and yarns
• Current Stage: 6060 - International Standard published
• Start Date: 29-Jan-2021
• Due Date: 22-Apr-2021
• Completion Date: 29-Jan-2021

Relations

• Revises: ISO 16549:2004 - Textiles — Unevenness of textile strands — Capacitance method
• Effective Date: 23-Apr-2020

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16549
Second edition
2021-01
Textiles — Unevenness of textile
strands — Capacitance method
Textiles — Irrégularité des fils textiles — Méthode capacitive
Reference number
ISO 16549:2021(E)
©
ISO 2021

---------------------- Page: 1 ----------------------
ISO 16549:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 16549:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 4
6 Atmosphere for conditioning and testing . 4
7 Sampling . 5
8 Procedure. 5
8.1 Setting of the apparatus . 5
8.2 Setting of the diagram scale . 5
8.3 Condenser assembly . 6
8.4 Selection of running speed . 6
8.5 Guiding facilities . 6
8.6 Twisting device . 6
8.7 Plot representing the linear density along the strand . 6
8.8 Preliminary run . 6
8.9 Test run . 6
9 Calculations and expression of results . 6
10 Test report . 7
Annex A (informative) Other methods for the determination of unevenness.8
Bibliography .10
© ISO 2021 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 16549:2021(E)

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 38, Textiles, Subcommittee SC 23, Fibres
and yarns.
This second edition cancels and replaces the first edition (ISO16549: 2004), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— correction of the description of test specimen length in 3.6 and 4.5;
— correction of the description of mass “normal” (“Gaussian”) distribution in 4.7;
— correction of the description of the measuring device in 5.2 and 8.3;
— description of a method for optimum twist application on multi-filament yarns in 5.2;
— designation of twisting device speed (if twist was applied) in Clause 10.
— review of grammar and linguistic consistency of definitions in Clauses 2 and 3.
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 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 16549:2021(E)

Introduction
In the 1960s, the International Wool Textile Organization (IWTO) prepared an unevenness method
[1]
destined for yarns and other strands made of wool. The method was adopted by ISO as ISO 2649 . It
contains a discussion of the principles of unevenness testing and refers to the then-popular unevenness
tester, the 1960s model of the Uster Evenness Tester, which was obsolete in mid-2000 when the present
[3]
International Standard was written. Later, the IWTO prepared a new method .
This document has mostly new wording but includes some elements of ISO 2649 and of IWTO-18-00.
© ISO 2021 – All rights reserved v

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16549:2021(E)
Textiles — Unevenness of textile strands — Capacitance
method
1 Scope
This document describes a method, using capacitance measuring equipment, for determining the
unevenness of linear density along the length of textile strands.
The method is applicable to tops, slivers, rovings, spun yarns and continuous filament yarns, made from
either natural or man-made fibres, in the range of 4 tex (g/km) to 80 ktex (kg/km) for staple-fibre
strands and 1 tex(g/km) to 600 tex (g/km) for continuous-filament yarns. It is not applicable to fancy
yarns or to strands composed fully or partly of conductive materials such as metals; the latter requires
an optical sensor (see A.4), and to raw silk filaments which are tested according to a specific standard.
The method describes the preparation of a variance-length curve, as well as the determination of
periodicities of linear density. It also covers the counting of imperfections in the yarn, namely of neps
and of thick and thin places.
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 139, Textiles — Standard atmospheres for conditioning and testing
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:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
unevenness
variation of linear density along the length of a continuous strand or yarn
Note 1 to entry: The term is also used occasionally for the variation of yarn diameter.
3.2
coefficient-of-variation unevenness
CV
u
value of unevenness (3.1) expressed as a coefficient of variation
Note 1 to entry: The coefficient-of-variation unevenness is expressed in percent, for example CV = 18,3 %.
u
Note 2 to entry: See also 4.6 and 4.7.
© ISO 2021 – All rights reserved 1

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ISO 16549:2021(E)

3.3
mean-deviation unevenness
U
u
value of unevenness (3.1) expressed as an average mean deviation
Note 1 to entry: The mean-deviation unevenness is expressed in percent, for example U = 14,6 %.
u
3.4
capacitor length
effective length of the capacitor in the direction of the specimen movement, usually 8 mm to 20 mm
3.5
length between
L
b
length of the test specimen for which the instrument takes an individual reading of mass
Note 1 to entry: The unevenness value decreases as L is increased.
b
Note 2 to entry: In the capacitance method, L is normally the capacitor length (3.4) but it can be increased
b
electronically.
Note 3 to entry: L is sometimes referred to in the literature as B.
b
3.6
length within
L
w
length of the test specimen for which an individual value of evenness is determined, and a reading is given
Note 1 to entry: The unevenness value increases as L is increased. When L is more than 100 m or so, then a
w w
further lengthening of L increases CV (or U ) only slightly.
w u u
Note 2 to entry: L is sometimes referred to in the literature as W.
w
3.7
total measured length
sum of all lengths within, L (3.6)
w
3.8
nep
tightly tangled knot-like mass of unorganized fibres
3.9
package
yarn wound to a shape, which can be supported (for example, bobbins, cones) or unsupported (for
example, skeins, cakes), suitable for conditioning and testing
3.10
spectrogram unit
attachment to unevenness testers for the calculation and presentation of periodic variations in the strand
3.11
thick place
yarn defect with linear density substantially (at least 50 %) greater than that of the adjoining segments
of the yarn and extending for at least 5 mm
3.12
thin place
yarn defect with linear density substantially (at least 50 %) smaller than that of the adjoining segments
of the yarn and extending for at least 5 mm
2 © ISO 2021 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 16549:2021(E)

4 Principle
4.1 A specimen is passed between two plates of a capacitor causing changes in capacitance which
are proportional to the changes of mass of the specimen. The instrument evaluates these changes and
reports them as coefficient-of-variation unevenness, CV , or mean-deviation unevenness, U .
u u
4.2 The fibre dielectric constant is also a factor determining the capacitance change. As long as the
dielectric constant is unchanging (non-blended strands or perfectly uniform blending), the dielectric
constant has no influence on the unevenness reading, which depends solely on the variation of mass.
If the dielectric constant differs for the types of fibres in a blend and if, at the same time, the blend is
irregular, then the reading of unevenness is increased above its true value. The interpretation of results
therefore requires caution.
4.3 Irregularities in the distribution of additives such as sizes, in moisture content and in fibre blending
can increase the measured unevenness above its true value.
4.4 Several studies have been conducted over the years (see Reference [4] for example) comparing the
true unevenness of a specimen, determined by cutting and weighing (see A.3.1), with the reading from an
unevenness tester. Good agreement was obtained, so the readings from the tester can be taken as being
the true unevenness value.
4.5 The value of unevenness has meaning only if both L and L are known and they should, in
w b
principle, always be reported, preferably as CV (L , L ).
u b w
EXAMPLE CV (10 mm, 1 000 m).
u
In practice, these two values are usually left unstated and are assumed to be those of the most commonly
used unevenness tester, namely:
— L : 8 mm for yarns, 12 mm for rovings, 20 mm for slivers and tops;
b
— L : total length of the test specimen (50 m for tops and slivers, 100 m for rovings, 400 m for yarns).
w
4.6 There are two possible expressions for unevenness, CV and U . The U is now obsolete and i
...

INTERNATIONAL ISO
STANDARD 16549
Second edition
Textiles — Unevenness of textile
strands — Capacitance method
Textiles — Irrégularité des fils textiles — Méthode capacitive
PROOF/ÉPREUVE
Reference number
ISO 16549:2020(E)
©
ISO 2020

---------------------- Page: 1 ----------------------
ISO 16549:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2020 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 16549:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 4
6 Atmosphere for conditioning and testing . 4
7 Sampling . 5
8 Procedure. 5
8.1 Setting of the apparatus . 5
8.2 Setting of the diagram scale . 5
8.3 Condenser assembly . 6
8.4 Selection of running speed . 6
8.5 Guiding facilities . 6
8.6 Twisting device . 6
8.7 Plot representing the linear density along the strand . 6
8.8 Preliminary run . 6
8.9 Test run . 6
9 Calculations and expression of results . 6
10 Test report . 7
Annex A (informative) Other methods for the determination of unevenness.8
Bibliography .10
© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii

---------------------- Page: 3 ----------------------
ISO 16549:2020(E)

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 38, Textiles, Subcommittee SC 23, Fibres
and yarns.
This second edition cancels and replaces the first edition (ISO16549: 2004), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— correction of the description of test specimen length in 3.6 and 4.5;
— correction of the description of mass “normal” (“Gaussian”) distribution in 4.7;
— correction of the description of the measuring device in 5.2 and 8.3;
— description of a method for optimum twist application on multi-filament yarns in 5.2;
— designation of twisting device speed (if twist was applied) in Clause 10.
— review of grammar and linguistic consistency of definitions in Clauses 2 and 3.
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 PROOF/ÉPREUVE © ISO 2020 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 16549:2020(E)

Introduction
In the 1960s, the International Wool Textile Organization (IWTO) prepared an unevenness method
[1]
destined for yarns and other strands made of wool. The method was adopted by ISO as ISO 2649 . It
contains a discussion of the principles of unevenness testing and refers to the then-popular unevenness
tester, the 1960s model of the Uster Evenness Tester, which was obsolete in mid-2000 when the present
[3]
International Standard was written. Later, the IWTO prepared a new method .
This document has mostly new wording but includes some elements of ISO 2649 and of IWTO-18-00.
© ISO 2020 – All rights reserved PROOF/ÉPREUVE v

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16549:2020(E)
Textiles — Unevenness of textile strands — Capacitance
method
1 Scope
This document describes a method, using capacitance measuring equipment, for determining the
unevenness of linear density along the length of textile strands.
The method is applicable to tops, slivers, rovings, spun yarns and continuous filament yarns, made from
either natural or man-made fibres, in the range of 4 tex (g/km) to 80 ktex (kg/km) for staple-fibre
strands and 1 tex(g/km) to 600 tex (g/km) for continuous-filament yarns. It is not applicable to fancy
yarns or to strands composed fully or partly of conductive materials such as metals; the latter requires
an optical sensor (see A.4), and to raw silk filaments which are tested according to a specific standard.
The method describes the preparation of a variance-length curve, as well as the determination of
periodicities of linear density. It also covers the counting of imperfections in the yarn, namely of neps
and of thick and thin places.
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 139, Textiles — Standard atmospheres for conditioning and testing
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:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
unevenness
variation of linear density along the length of a continuous strand or yarn
Note 1 to entry: The term is also used occasionally for the variation of yarn diameter.
3.2
coefficient-of-variation unevenness
CV
u
value of unevenness (3.1) expressed as a coefficient of variation
Note 1 to entry: The coefficient-of-variation unevenness is expressed in percent, for example CV = 18,3 %.
u
Note 2 to entry: See also 4.6 and 4.7.
© ISO 2020 – All rights reserved PROOF/ÉPREUVE 1

---------------------- Page: 6 ----------------------
ISO 16549:2020(E)

3.3
mean-deviation unevenness
U
u
value of unevenness (3.1) expressed as an average mean deviation
Note 1 to entry: The mean-deviation unevenness is expressed in percent, for example U = 14,6 %.
u
3.4
capacitor length
effective length of the capacitor in the direction of the specimen movement, usually 8 mm to 20 mm
3.5
length between
L
b
length of the test specimen for which the instrument takes an individual reading of mass
Note 1 to entry: The unevenness value decreases as L is increased.
b
Note 2 to entry: In the capacitance method, L is normally the capacitor length (3.4) but it can be increased
b
electronically.
Note 3 to entry: L is sometimes referred to in the literature as B.
b
3.6
length within
L
w
length of the test specimen for which an individual value of evenness is determined, and a reading is given
Note 1 to entry: The unevenness value increases as L is increased. When L is more than 100 m or so, then a
w w
further lengthening of L increases CV (or U ) only slightly.
w u u
Note 2 to entry: L is sometimes referred to in the literature as W.
w
3.7
total measured length
sum of all lengths within, L (3.6)
w
3.8
nep
tightly tangled knot-like mass of unorganized fibres
3.9
package
yarn wound to a shape, which can be supported (for example, bobbins, cones) or unsupported (for
example, skeins, cakes), suitable for conditioning and testing
3.10
spectrogram unit
attachment to unevenness testers for the calculation and presentation of periodic variations in the strand
3.11
thick place
yarn defect with linear density substantially (at least 50 %) greater than that of the adjoining segments
of the yarn and extending for at least 5 mm
3.12
thin place
yarn defect with linear density substantially (at least 50 %) smaller than that of the adjoining segments
of the yarn and extending for at least 5 mm
2 PROOF/ÉPREUVE © ISO 2020 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 16549:2020(E)

4 Principle
4.1 A specimen is passed between two plates of a capacitor causing changes in capacitance which
are proportional to the changes of mass of the specimen. The instrument evaluates these changes and
reports them as coefficient-of-variation unevenness, CV , or mean-deviation unevenness, U .
u u
4.2 The fibre dielectric constant is also a factor determining the capacitance change. As long as the
dielectric constant is unchanging (non-blended strands or perfectly uniform blending), the dielectric
constant has no influence on the unevenness reading, which depends solely on the variation of mass.
If the dielectric constant differs for the types of fibres in a blend and if, at the same time, the blend is
irregular, then the reading of unevenness is increased above its true value. The interpretation of results
therefore requires caution.
4.3 Irregularities in the distribution of additives such as sizes, in moisture content and in fibre blending
can increase the measured unevenness above its true value.
4.4 Several studies have been conducted over the years (see Reference [4] for example) comparing the
true unevenness of a specimen, determined by cutting and weighing (see A.3.1), with the reading from an
unevenness tester. Good agreement was obtained, so the readings from the tester can be taken as being
the true unevenness value.
4.5 The value of unevenness has meaning only if both L and L are known and they should, in
w b
principle, always be reported, preferably as CV (L , L ).
u b w
EXAMPLE CV (10 mm, 1 000 m).
u
In practice, these two values are usually left unstated and are assumed to be those of the most commonly
used unevenness tester, namely:
— L : 8 mm for yarns, 12 mm for rovings, 20 mm for slivers and tops;
b
— L : total length of the test specimen.
w
4.6 There are two possible expressions for unevenness, CV and U . The U is now obsolete and its use,
u u u
while permitted, is discouraged. CV i
...