Help with separating magnets

[jaredye]

So I bought 50 N50 and 200 N35 magnets from magnets365.com and they just put them all together. I have no way to tell them apart just from the appearance. Does anyone know a relative quick method to tell which is which without using intricate instruments?

 

[AlphaSheep]

Get some sheets of paper. Place one sheet against your refrigerator door and stick all the magnets to it. Remove the magnets. Add another sheet of paper, then try stick all the magnets to it. Add a third sheet of paper and repeat. Eventually you will reach a point where the 50 stronger magnets will stick and the 200 weaker ones won't.

Just don't let the magnets drop to the floor. Neodymium magnets break easily, and lose a little magnetism from hard impact.

 

[SenorJuan]

You could also try a similar idea, with magnet stuck to magnet. You will have three strengths of attraction: weak-weak, weak-strong, strong-strong. This will allow you to find a 'reference' strong one, and weak one, from which you can identify the others. A possible practical arrangement may be to have one above and one below some thick card etc. Moving one drags the other around, try more card, see the difference.

If you can get hold of a magnetic compass this should work:
Sit the compass down flat so it's pointing North. Bring a magnet up to it from the North direction (precisely), there will be a point where the magnet exactly cancels the Earth field and the needle flips round. Make a note of the distance. Stronger magnets will have a greater seperation distance.

 

[jaredye]

I've been trying similar methods but it doesn't seem to work. I suspect that by sticking to each other for so long their magnetic strength has somehow homogenized. So when I take out a piece from this pile the strength of every piece is somewhat similar, and it might take quite a while for it to restore to its normal strength.

Of course I'm not an expert in magnets. Can someone tell me if this is possible?

 

[SenorJuan]

No, it's not possible, NIB magnets are pretty resistant to most normal ways of demagnetising them.
But the difference between your two types is not massive, so you are looking for maybe 20% difference in some characteristic.

Do you think there's any physical difference between the two? Do you have access to any lab scales, eg with 0.001 gram resolution? There may be some unit to unit variation, but you could still seperate them into two groups.

I guess you don't want to go all techy, and salvage Hall Effect sensors out of scrap CD-ROM / floppy-disk drives etc ?