Stone detection method and apparatus for harvester

An agricultural harvester having a header with a reel and an auger, wherein the reel and the auger provide crop material to an elevator and a foreign object detecting mechanism, wherein the foreign object detecting mechanism includes a foreign object detecting circuit for detecting foreign objects and an object extrusion mechanism operationally connected to be activated by the detecting circuit, wherein the detecting circuit comprises:

• a first vibration sensor that generates a first signal in response to vibrations generated by a foreign object;
• a programmable amplifier that receives the first signal and generates an amplified first output signal;
• a frequency bandpass filter that receives and filters a bandwidth of the first output signal to generate a first frequency filtered signal;
• a variable threshold comparator that receives the first frequency filtered signal and generates a second output signal when the first frequency filtered signal exceeds a minimum threshold amplitude;
• a pulse rejection network that receives the second output signal and generates an internal signal when the pulse train frequency of the second output signal falls within a specified bandwidth frequency range;
• and
• a microprocessor that includes the pulse rejection network and that is electronically connected to the threshold comparator and to the programmable amplifier, wherein the microprocessor operates to control the value of the minimum threshold amplitude of the threshold comparator and to control the magnitude of signal amplification performed by the programmable amplifier, wherein the detecting circuit activates the object extrusion mechanism whenever the microprocessor generates a third output signal in response to the internal signal.