Textiles -- Unevenness of textile strands -- Capacitance method

ISO 16549:2004 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 require an optical sensor. ISO 16549:2004 describes the preparation of a variance-length curve, as well as the determination of periodicities of linear density, and covers also 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
Replaced
Publication Date
25-May-2004
Withdrawal Date
25-May-2004
Current Stage
9599 - Withdrawal of International Standard
Completion Date
26-May-2004
Ref Project

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INTERNATIONAL ISO
STANDARD 16549
First edition
2004-06-01
Textiles — Unevenness of textile
strands — Capacitance method
Textiles — Irrégularité des fils textiles — Méthode capacitive
Reference number
ISO 16549:2004(E)
ISO 2004
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ISO 16549:2004(E)
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© ISO 2004

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Published in Switzerland
ii ISO 2004 – All rights reserved
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ISO 16549:2004(E)
Contents Page

1 Scope .................................................................................................................................................... 1

2 Normative references .......................................................................................................................... 1

3 Terms and definitions .......................................................................................................................... 1

4 Principle ................................................................................................................................................ 2

5 Apparatus ............................................................................................................................................. 3

6 Atmosphere for conditioning and testing ......................................................................................... 4

7 Sampling ............................................................................................................................................... 4

8 Procedure ............................................................................................................................................. 5

9 Calculations and expression of results ............................................................................................. 6

10 Test report ............................................................................................................................................ 6

Annex A (informative) Other methods for the determination of unevenness ......................................... 8

Bibliography ............................................................................................................................................... 10

ISO 2004 – All rights reserved iii
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ISO 16549:2004(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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 16549 was prepared by Technical Committee ISO/TC 38, Textiles, Subcommittee SC 23, Fibres and yarns.

This International Standard cancels and replaces ISO 2649 which is now obsolete.
iv ISO 2004 – All rights reserved
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ISO 16549:2004(E)
Introduction

In the 1960s the International Wool Textile Organization (IWTO) prepared an unevenness method destined for

yarns and other strands made of wool. The method was adopted by ISO as ISO 2649:1974. 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 International Standard

was written. Later, the IWTO prepared a new method, IWTO-18-00, published in 2000.

ISO 16549 has mostly new wording but includes some elements of ISO 2649 and of IWTO-18-00 – with thanks

to IWTO.
ISO 2004 – All rights reserved v
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INTERNATIONAL STANDARD ISO 16549:2004(E)
Textiles — Unevenness of textile strands — Capacitance method
1Scope

This International Standard 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 require an optical sensor (see A.4).

The method describes the preparation of a variance-length curve, as well as the determination of periodicities

of linear density. It covers also the counting of imperfections in the yarn, namely of neps and of thick and thin

places.

Irregularities in the distribution of additives such as sizes, in moisture content and in fibre blending may increase

the measured unevenness above its true value.
2 Normative references

The following referenced documents are indispensable for the application 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.
3.1
unevenness
variation of linear density along the length of a continuous strand or yarn
NOTE The term is also used occasionally for the variation of yarn diameter.
3.2
coefficient-of-variation unevenness
value of unevenness (3.1) expressed as a coefficient of variation

NOTE 1 The coefficient-of-variation unevenness is expressed in percent, for example CV = 18,3 %.

NOTE 2 See also 4.5 and 4.6.
3.3
mean-deviation unevenness
value of unevenness (3.1) expressed as an average mean deviation

NOTE 1 The mean-deviation unevenness is expressed in percent, for example, U = 14,6 %.

ISO 2004 – All rights reserved 1
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ISO 16549:2004(E)
NOTE 2 See also 4.5 and 4.6.
3.4
capacitor length

effective length of the capacitor in the direction of the specimen movement, usually 8mm to 20mm

3.5
length between

length of the test specimen for which the instrument takes an individual reading of mass

NOTE 1 The unevenness value decreases as L is increased.

NOTE 2 In the capacitance method, L is normally the capacitor length but it can be increased electronically.

NOTE 3 L is sometimes referred to in the literature as B.
3.6
length within

length of the specimen for which an individual value of unevenness is determined and a reading is given

NOTE 1 The unevenness value increases as L is increased. When L is more than 100 m or so, then a further

w w
lengthening of L increases CV (or U ) only slightly.
w u u
NOTE 2 L is sometimes referred to in the literature as W .
3.7
total measured length
sum of all measured lengths L
3.8
nep
tightly tangled knot-like mass of unorganized fibres
3.9
package

yarn wound to a shape, which may be supported (for example, bobbins, cones) or unsupported (for example,

skeins, cakes), suitable for conditioning and testing
3.10
spectrogram

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 5mm
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 5mm
4Principle

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 CV or U .
u u
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ISO 16549:2004(E)

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 Several studies have been conducted over the years, see Reference [3] 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.

4.4 The value of unevenness has meaning only if both L and L are known and they should, in principle,

b w
always be reported, preferably as CV (L , L ).
u b w
EXAMPLE CV (10 mm, 1 000 m).

In practice, these two values are usually left unstated and are assumed to be those of the most commonly used

unevenness tester, namely
— L : 8mm for yarns, 12mm for rovings, 20mm for slivers and tops;
— L : total length of yarn on the package.

4.5 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 is the preferred expression.

4.6 If mass is distributed near to “normal”, then the ratio of CV /U is approximately 1,25. This conversion

u u

factor must be used cautiously because, in case of departures from normality, the ratio can be considerably

different. The conversion factor may be used to convert a table of quality levels from U to CV .

u u

4.7 When is plotted against , a “variance-length curve” is obtained which gives additional information

CV L
u b

on the material's unevenness. When the plot is made on log-log paper, then the curve is almost a straight line

and its slope gives information on the relationship between short-term and long-term unevenness.

4.8 Unevenness testers usually contain a spectrogram, which analyses the data and provides information on

periodic variations of linear density. This information is useful in finding faults in the processing. The analysis

uses an algorithm based on the Fourier transformation.

4.9 Unevenness testers usually contain a counter for yarn imperfections, namely neps, and thick and thin

places. The level beyond which the imperfections are counted can be adjusted.

4.10 Unevenness is a fundamental feature of yarn construction. It influences the efficiency of processing as

well as fabric appearance. Lower unevenness generally results in a better-looking fabric but the relation is not

simple and interpretation requires special care.
5 Apparatus

5.1 Different types of apparatus are in use for measuring strands made of staple fibres and filament yarns.

5.2 The apparatus consists of the following elements:
a) measuring device, featuring
— several measuring condensers, usually grou
...

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