分析筛 精确筛分分析的最高精度

For reliable and reproducible results in the context of quality assurance, the use of test sieves which correspond to the standards ISO 3310 or ASTM E11 is essential. The technical requirements and monitoring for test sieves are laid down in these standards. If a laboratory carries out quality control in accordance with ISO 9000 ff, the sieve shakers, test sieves and all other involved instruments (e.g. scales) have to be subjected to test agent monitoring. The standard ISO 3310 stipulates which tolerances are allowed for the wire diameter (d) of the woven sieve fabric and for the nominal mesh width (w) of the apertures.

For each mesh width w the value y is defined which indicates how much the mean real mesh width may differ from the nominal mesh width. This can be demonstrated with a 63 μm sieve. The tolerance y for a sieve with the nominal mesh width 63 μm is ±3.7 μm. This means that the mean value of the mesh sizes must lie between 59.3 μm and 66.7 μm. A look at the graph that helps to understand why the knowledge of the real mesh width is so important for sieve analysis: if the mesh size is 63 μm, 40% of the sample are smaller than 63 μm. If, however, the mean real mesh width is 66.7 μm, 44% of the particles are smaller than 66.7 μm. If a user does not know the real mesh width, he would assume that 44% of the sample is smaller than 63 μm.