There has been much speculation about large magnetic fields physically distorting reed switches when the magnetic fields are brought into the proximity of a reed switch or reed switch sensor. In fact, the tiny nickel/iron ferromagnetic blades will reach a magnetic saturation point and increasing the external magnetic field will have no effect on the reed blades. One can use the analogy of filling a glass of water. Once it is full, no matter how much more water users try to pore into the glass, it will not accept any additional water.