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- Feb 1, 2015
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I dedicated one of my 100/140 w soldering guns for demagnetizing. Instead of the soldering tip, I used a 1-1/2" diameter single turn loop of 10 AWG copper wire (about 5"). With magnetizing/demagetizing coils, it's all about ampere-turns. Ten turns carrying 1 amp is equivalent to 1 turn carrying 10 amps.
Magnetic flux is proportional to amp-turns. My single turn demagnetizer reads about 310 amps on clamp-on ammeter and the magnetic flux is 310 amp-turns. 10AWG has a resistance of about 1 milliohm/ft. so my loop has a total resistance of about .4 milliohms. If I used a two loops with a total resistance of .8 milliohms, I would expect the current to drop to around 155 amps but I would still have 310 ampere-turns. So, with 3 turns and 15 inches of wire, the current would be just over 100 amps but the magnetic flux would still be 310 amp-turns.
The 1-1/2" loop is great for demagnetizing screwdrivers and small wrenches but I sometimes have a need to demagnetize larger items. I can't just take the 10" of 10 AWG wire and make a 3" diameter loop because although the current draw is the same as for the smaller loop with two turns, I now have just a single turn so the magnetic flux has dropped to 155 amp-turns.
However, I go to a larger wire size, say 7AWG, the resistance will drop to .5 milliohms/ft and the resistance of my 3" loop will .4 milliohms. The current will be 310 amps and magnetic flux for this 3" loop will be 310 amp-turns, as before. Actually, since 7AWG wire is not a common size, I would probably use 12" of 6AWG for a resistance of .4 ohms and a diameter of 3.8". Note that the larger wire won't fit the soldering gun as is. I would have to make adapter studs which would thread into my gun and provided a post for the 6AWG wire.
Magnetic flux is proportional to amp-turns. My single turn demagnetizer reads about 310 amps on clamp-on ammeter and the magnetic flux is 310 amp-turns. 10AWG has a resistance of about 1 milliohm/ft. so my loop has a total resistance of about .4 milliohms. If I used a two loops with a total resistance of .8 milliohms, I would expect the current to drop to around 155 amps but I would still have 310 ampere-turns. So, with 3 turns and 15 inches of wire, the current would be just over 100 amps but the magnetic flux would still be 310 amp-turns.
The 1-1/2" loop is great for demagnetizing screwdrivers and small wrenches but I sometimes have a need to demagnetize larger items. I can't just take the 10" of 10 AWG wire and make a 3" diameter loop because although the current draw is the same as for the smaller loop with two turns, I now have just a single turn so the magnetic flux has dropped to 155 amp-turns.
However, I go to a larger wire size, say 7AWG, the resistance will drop to .5 milliohms/ft and the resistance of my 3" loop will .4 milliohms. The current will be 310 amps and magnetic flux for this 3" loop will be 310 amp-turns, as before. Actually, since 7AWG wire is not a common size, I would probably use 12" of 6AWG for a resistance of .4 ohms and a diameter of 3.8". Note that the larger wire won't fit the soldering gun as is. I would have to make adapter studs which would thread into my gun and provided a post for the 6AWG wire.