Automatic Dirt Counting Using Transmitted Light - Some Results, 1998 Process & Product Quality Conference Proceedings

In the future instruments will be widely used for the inspection of contraries in pulp, preferentially for pulps containing large numbers of contraries. However, it should be noted that the results obtained by visual inspection may not be equivalent to those found by instrumental dirt counting. This paper presents some results of automatic dirt counting employing transmitted light and wet samples. The measurements have been carried out according to the new ISO standards, which permit the use of instrumental devices in dirt counting. According to our experiments, the correlation between visual and automatic dirt counting seems to be 75 - 90% when wetted samples are inspected in transmitted light. The repeatability and detection limits of instrumental inspection depend greatly on the equipment used, although in our experiments the coefficient of variation was in most cases smaller than 15%. The small number of instruments able to use transmitted light made it difficult to measure the reproducibility between different image analyzers. Some results obtained with two different automatic dirt counters are presented.