@Dr Zaius Why would he want to decrease (degauss) the strength of the magnets after he chose high strength ones in the first place?..
4 meters is the far est away my cell phone sensor can pick up the em feilds from the em pump and with the smaller one less i think as strange as it is , so the hdr electromagnet and em pump fields react the same to the cell phone sensor its not the electrical its the magnetic fields its sensing , nothing else to prove just that i get same sensor results with hdr electromagnet as i do with the em pump, at 4 meters away i watch the needle movement and as i move closer it gets to the spot where the beeper starts beeping, i can try the magnetized needle floating on salt water if i want absolute max rangeWhat are you trying to prove though Steve, and what exactly do you mean about the reaction to your cell phone sensor?
It seems to me that your cell phone is just picking up some electrical interference from the EM pump, similar to what is happening to your watch mate..but what exactly are you trying to do?