Abstract: An apparatus for measuring the volume rate of flow of flowing fluids by means of a flow meter, called rotameter, in which a linear light source and a plurality of light sensing means are engaged along diametrically opposing generatrices of the transparent measuring tube of the rotameter, and the float in the measuring tube intercepts the light path so that the state of illumination of the light sensing means corresponds to the position of the float in the rotameter tube, and the outputs of the light sensing means are combined in a logical circuit to produce a signal combination representing said float position.

Abstract: An instrumental measuring method for determining the size-distribution of grained material is described in which the material is evenly distributed in a fluid then the fluid is let in rest state when the materials gets sedimenting, and during sedimentation the hydrostatic pressure is continuously measured in at least two height regions of the fluid preferably by appropriate pressure sensitive transistors and the difference of the measured hydrostatic pressures is characteristic of the size-distribution of the grained material on the basis of the well-known Stokes' relation.