The Foreign Object in this case is a 3.5″ cube of wood.
The ‘Sensor View’ shows the sensor move upward as the foreign object in the right clip reaches the front feed rolls.
The substantially uncompressable object causes a displacement of the upper feedroll at an acceleration rate greater than the substantially more compressable crop flow does. This threshold of displacement acceleration, or inertia, is the desired setting of the sensor. Thus differentiating between crop lumps and stones etc.