Metal detectors have been used in food plants for decades and operation is based on a
magnetic field
within a tunnel. Metal objects within the field interfere with the magnetic field
indicating an
unwanted inclusion. Performance of the metal detector does vary depending on the
size of the aperture
and the product.
Metal detectors are very good at detecting both ferrous and non-ferrous foreign
objects, but have
limited capacity with stainless steel. X-ray systems on the other hand have an
outstanding detection
capacity with all metals except aluminum.