Typically, 1000 metres of yarn is used to determine mass deviations along the yarn and is graphically represented in a mass diagram. By using a fourier transformation on the mass diagram periodicities can be observed, which can be traced back to processing parameters. In some cases this leads to revealing flaws in the spinning process.
An example where this analysis could be very helpful; if a decrease in mass is seen every 100 meters, and a melt pump revolves once every 100 meters. A defect in the melt pump could very well be the reason of the periodically decrease in mass.