ISO Standard Method Research Articles

The Measurement of Carpet-pile Thickness Part I: Evaluation of the WRONZ Pile Thickness Probe by an Inter-laboratory Trial

An inter–laboratory trial involving ten laboratories is reported and shows that the WRONZ Pile Thickness Probe can be used to make accurate and repeatable measurements of pile thickness over a wide range of carpet types and pile fibres. The major source of variation in mean pile–thickness estimates is attributed to the carpet specimens themselves and is due to differences (small) between the carpet specimens and variations (relatively large) within a single carpet specimen. Together these components of variation account for about 75% of the total variance observed in the trial. Variations were also found between laboratories; these were relatively small, and analysis of the results suggests that they were due in approximately equal parts to (i) differences between Pile Thickness Probes, (ii) differences between modes of operation, and (iii) other factors, which could not be fully identified or quantified. The effects of within–carpet–specimen variation can be reduced simply by making more measurements of pile thickness. With very variable carpets, large numbers of measurements would be required to obtain a high level of precision (e.g.,±0.2 mm). This would be impracticable under the existing ISO standard test method but is quite feasible by use of the WRONZ Pile Thickness Probe.