A magnetic apparatus (1) comprising a magnetizable surface (2) configured to anchor a one or more ferromagnetic elements in a removable manner and a plurality of magnetic poles (3), each provided with a free surface (4) thereof, the magnetizable surface (2) being at least partially defined by the free surfaces (4) of said plurality of magnetic poles (3) placed side by side; one part of said magnetic poles (3) has at least two measuring areas (5) on the free surface thereof, each measuring area (5) being associated with at least one sensor (6) adapted to detect a magnetic flux exiting from said area.