NBN ISO 16549:2021

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.