The on-line fineness meter is indispensable to design fully automatic cement grinding system and to save energy in the system. Several on-line fineness meters have been reported, but their prices, as well as durability and accuracy made their users hesitate to apply them. Bearing these points in mind, the authers have developed a new on-line fineness meter. It consists of a pilot air classifier, a balance with two belt conveyors functioning as the scale pan. These conveyors transport powder streams, i.e. classifier feed and coarse particles after classification. Through controling of the classifier cut-size, the ratio of flow rate of these two streams is kept constant automatically. As the result, the fineness of the sample can be indicated by the cut-point. From the test on a grinding system, following have been obtained:
(1) accuracy
the standard deviation of measured residue on 26μ: 0.6% (This corresponds to Blain specific surface area 30cm²/g)
(2) indicial response
the time constant: about 10min.