A MP Magnetic Pickup consists of a permanent magnet, a pole‑piece, and a sensing coil encapsulated in a cylindrical case. An object (target) of iron, steel, or other magnetic material, passing closely by the pole‑piece causes distortion of the magnetic flux field, which in turn generates a signal voltage. The magnitude of the signal voltage depends on the relative size and magnetism of the target, its speed of approach, and how close it passes the pole‑piece.
