Description: It was made an analysis of the possibilities to reduce the uncertainty in assessing the quality of raw cotton by the standard method (GOST 3813-72). It was given the mathematical treatment of data, which was obtained in establishing the technological variety of the cotton yarn by polarizing microscopy using a universal compensating plate – quartz wedge. The analysis of the results showed that the use of an improved method of polarization microscopy to assess the quality of yarn fibers can reduce the value of uncertainty of result. It was established that the results provided by the measurement of 50 or more fibers. With the purpose of the technical and economic feasibility was proposed to increase the number of the measured fibers up to 80 – 100 pieces.
Keywords: measurement uncertainty, the method of assessing the quality of cotton fiber, yarn, number of measured fibers, polarizing microscope, universal compensator