Experiments with Acoustic Sensors for Grain Loss Measuring on Combines

A metallic thin plate, where the straw from the grain separation process are thrown, piezoelectric disks attached at this plate, and signal processing circuits, together form a grain loss detection system to the grain extracting efficiency measurement. The sound spectrum analysis applied to the acoustic signals generated by the shock against to the plate, shows that some physical characteristics that distinguish grains from straw, like greater density and less relative size, are visible in the sound spectrum. This characteristics provide a greater energy in the high frequency spectrum so this can be used to electronically distinguish individual grains, among the straw, in intervals as short as 1 ms, providing an almost perfect grain loss counting.