Comparisons Between OFDA4000 and IWTO Standardised Methods for Measurements Made on Wool Tops: Part 1 Diameter Characteristics

Abstract

A comparison of the measurement of OFDA4000 and the IWTO Standardised Laserscan on 601 commercial tops from the TEAM-3 project and 301 research tops derived from the processing of single sale lots has been completed. The three measurements considered were Mean Fibre Diameter (MFD), the Standard Deviation of Diameter (SD) and the Coefficient of Variation of Fibre Diameter (CVD).

Evidence is presented that shows that the SD measured by Laserscan and OFDA100 are not equal and for the purpose of comparison the Laserscan SD was modified mathematically to give an OFDA100 equivalent (SDm). The Laserscan CVD was also modified to give an OFDA100 equivalent (CVDm). The modification reduced the size of the observed differences.

In the case of the TEAM-3 comparisons average differences were found for all three parameters examined (MFD +0.16µm; SDm -0.11 µm; CVDm -0.68%). The respective SD of differences between the measurement systems gives an indication of the spread around the average difference for each parameter (SD of Differences (MFD 0.14µm; SDm 0.10µm; CVDm 0.45%). The Standard Deviation of Differences for MFD was consistent with what could be expected from the Airflow apparatus. This means that 95% of the comparisons were within the following: MFD -0.1µm to +0.4µm; SDm -0.3µm to +0.1µm; CVDm -1.6% to +0.2%. There was no evidence of any level dependency in the observed differences for MFD, SDm or CVDm.

In the case of the Single Sale Lot comparisons average differences were found for all three parameters examined (MFD +0.17µm; SDm -0.04 µm; CVDm -0.37%). These were close to the values found for TEAM-3. The respective SD of differences between the measurement systems gives an indication of the spread around the average difference for each parameter (SD of Differences (MFD 0.16µm; SDm 0.12µm; CVDm 0.60%). These results were slightly higher than those found for the TEAM-3 tops. The Standard Deviation of Differences for MFD was consistent with what could be expected from the Airflow apparatus. This means that 95% of the comparisons were within the following: MFD -0.1µm to +0.5µm; SDm -0.3µm to +0.1µm; CVDm -1.6% to +0.8%. In contrast to the TEAM-3 tops all three parameters (MFD, SDm or CVDm) for the Sale Lot tops exhibited level dependencies in the observed differences. 

Citation

"Comparisons Between OFDA4000 and IWTO Standardised Methods for Measurements Made on Wool Tops: Part 1 Diameter Characteristics", V.E. Fish, A. Balasingam, J.W. Marler, T.J. Mahar, Report SG 02, Technology & Standards Committee, Sliver Group, Biella Meeting, November 2005