Variable sensitivity metal detection system

摘要

In a forage harvester having a metal detector positioned within a first feed roll and a second feed roll whose displacement from the first feed roll varies with the bulk of crop material passing between the feed rolls, the sensitivity of the metal detector is adjusted according to the displacement of the second feed roll from the metal detector to provide a more uniform detection of tramp metal with varying crop bulk. The sensitivity is increased as the inherent noise component induced in the metal detector output signal by the second feed roll decreases as the second feed roll is displaced from the metal detector by crop bulk.