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.nd 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 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