GB/T 3292.1-2008 Textiles — Unevenness of textile strands — Part 1: Capacitance method
1 Scope
This part of GB/T 3292 specifies a method, using capacitance measuring equipment, for determining the unevenness of linear density along the length of textile strands.
This part is applicable to staple-fibre strands and continuous filament yarns. The determination range is 4 tex to 80 ktex for staple-fibre strands and 10 dtex to 1670 dtex for continuous-filament yarns. This part is not applicable to fancy yarns or to strands composed fully or partly of conductive materials such as metals; the latter can be determined by the photoelectricity method (see Part 2 of GB/T 3292).
This part 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.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of GB/T 3292. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this part. However, parties to agreements based on this part are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest editions of the normative document referred to applies.
GB/T 6529 Textiles - Standard atmospheres for conditioning and testing (GB/T 6529-2008, ISO 139:2005, MOD)
3 Terms and definitions
For the purpose of this part of GB/T 3292, 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
CVm
percentage of ratio of standard deviation of yarn linear density to the mean linear density within the total test length
3.3
mean deviation unevenness
Um
Percentage of the general average of absolute value of the difference between density values of various yarn and mean linear density within the length to the mean linear density within the total testing length in accumulated testing length
3.4
capacitor length
effective length of the capacitor in the direction of the specimen movement, usually 8mm to 20mm
3.5
length between
Lb
length of the test specimen for which the instrument takes an individual reading of mass
Note 1: The unevenness value decreases as Lb is increased.
Note 2: In the capacitance method, Lb is normally the capacitor length but it can be increased electronically.
Note 3: Lb is sometimes referred to in the literature as B.
3.6
length within
Lw
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 Lw is increased. When Lw is more than 100m or so, then a further lengthening of Lw increases CVm only slightly.
Note 2: Lw is sometimes referred to in the literature as W.
3.7
spectrogram
one of the frequency domain representations of the variation in yarn linear density. Its horizontal axis (in logarithmic scale) represents the wavelength of the periodic unevenness, and the vertical axis (linearly) represents the relative average amplitude of the periodic unevenness, describing the periodic variation of the yarn
Contents
Foreword II
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Apparatus
6 Standard atmosphere
7 Sampling
8 Procedure
9 Calculation and expression of results
10 Test report
