When it comes to level measurement, flours are anything but easy to measure. For one thing, huge amounts of dust are generated during filling and the dust cloud settles only very slowly inside the silo. For another, the approximately 120 different flours all differ somewhat in their dielectric constant. Karl Dahlke, manager of the flour silos and batch logistics at Swissmill, and his deputy Simon Rochat agree that bran is the most difficult product to measure: "It has an Epsilon value of only 1.4 in the summer." And the fact that this material is stored in a very slender, 10 m high reinforced concrete silo makes precise level measurement even more difficult.
Over the years, new level sensors from VEGA were often tested here. One difficulty was that the cable of guided microwave sensors would occasionally unravel, allowing individual product grains to get stuck in it. This generated incorrect measurement signals. In the meantime this instrument type has been replaced by VEGAPULS 69
with 80 GHz operating frequency. It measures without contact and can reliably detect the medium even through thick clouds of dust.