The invention relates to a method for
quality monitoring of longitudinally moving
yarn at workplace of
textile machine manufacturing cross-coil, wherein, the
yarn fault is, related to the
diameter deviation and longitudinal length of the
yarn, estimated in the yarn by aid of an inspecting apparatus and an estimating apparatus, which is realized by comparing the
diameter deviation with the clearing threshold value and removing the deviations positioned over the clearing threshold value, wherein, a width is set in a coordinate
system for the position of the clearing threshold value and definedby an upper limit and a
lower limit, wherein, the fluctuation of the
diameter under the
lower limit can not be estimated into the yarn fault, while each yarn fault over the upper limit is removed, andbased on the given yarn quality each time on the
station, the clearing threshold value is changed in the way that the amount of the yarn fault located between the clearing threshold value and the
lower limit and therefore being retained in the yarn can not exceed that of the predetermined yarn fault in the yarn in a
unit of length or plane fabric in a
unit of length made of the yarn dependent onthe quality.