On-Line Volume Measurement Of Bulk Materials

The authors will describe a technique initially developed for automatic inspection and gauging of extruded products which has more recently been applied to on-line volume measure-ment of bulk materials carried on conveyor belts. The technique involves a light-sectioning optical system in which a straight edge of light is projected across the direction of flow. When viewed from a different angle, this edge is seen to follow the external profile of the material, and this view is imaged onto a two-dimensional photodiode array. Processing of the array output signal with an electronic system including a microprocessor enables the instantaneous cross-sectional area of the load to be computed, since the underside profile formed by the empty conveyor belt is known. Integration of these measurements over a given length of conveyor movement yields a measurement which is proportional to volume.