BS ISO 2648:2020 pdf download

BS ISO 2648:2020 pdf download.Wool — Determination of fibre length distribution parameters — Capacitance method
1  Scope
This document specifies a method for the determination of fibre length distribution parameters (principally mean length, expressed as Hauteur or Barbe, and the coefficient of variation of the measurement) on slivers and rovings made from combed wool or combed synthetic fibres.
As the fibres of different chemical structure have different di-electric values, the method is not directly applicable to slivers made up of a blend of wool/synthetic fibres.
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 Hauteur
H
mean cross-section biased length of the test specimen
Note 1 to entry: It is expressed in millimetres (mm).
3.2 Barbe
B
mean weight-biased length of the test specimen
Note 1 to entry: It is expressed in millimetres (mm).
Note 2 to entry: Only Hauteur is certifiable.
3.3 total sample
total of the laboratory samples (3.4) taken to represent the lot
[SOURCE: ISO 137:2015, 3.2, modified — The definition has been slightly modified.]
of the fibres provides for a detailed examination of the local mass from the end of the sample up to the line of the common origin of the fibres. A carriage automatically carries the test specimen at a constant speed between the electrodes of the measuring condenser, or conversely the condenser moves over the test specimen.
5.1.3  Recorder.
In the analogue system, the record is a galvanometric recorder, which automatically traces the cumulative Hauteur diagram on squared paper during measurement. In the digital system, the data are captured by a computer which is capable of outputting the results to either the screen or to a printer. The diagram ordinate gives the percentage of fibres (biased by cross- section) of length greater than the length indicated on the corresponding abscissa. (The percentage by cross-section is very close to the percentage by number).
5.2  Test specimen holder.
5.3  Extractor system.
5.4  Restraining strip.
6  Conditioning and testing atmosphere