An investigation of the sampling bias of the beard method as used in HVI^™

Abstract

The beard method is used for sampling cotton fibers to generate fibrograms from which length parameters can be obtained. It is the sampling method used by the Uster High Volume Instrument (HVI^™). A fundamental issue of this sampling method is its bias since the mathematical computation to obtain length parameters is quite different. There have been different assumptions regarding the bias of the beard sampling method. In our experiments, we have seen discrepancies in measurements that cannot be explained as length‐biased or unbiased, especially in the short fiber region. We report a fundamental research, including experimental and theoretical analysis, and computer simulations, that reveals the bias due to this sampling method. We find that the beard sampling method as used in HVI is not completely length‐biased; fibers sampled by using this method are similar to the original fibers except in the short fiber region. Short fiber content (SFC) of the sampled fiber is lower than that of the original fiber, and this difference is inherently introduced by the sampling method.

Keywords:

• cotton
• HVI
• beard method
• fiber length measurement
• sampling bias
• short fiber content

Acknowledgements

The authors would like to thank Cotton Incorporated for financially supporting a project on improving cotton quality measurement, of which this research is a component.