FEMM - What's wrong with this picture? 2

[Nergus]

I'm open to being told what I've done wrong here!
Quite new to FEMM and self-taught - by an idiot.
I've modelled a static array of 13-off 3/8" NIB cube-magnets in N52, arranged alternate North and South at the top.
An analysis of flux density at a couple of mm above this array shows 12 'lobes' of flux (IBI) corresponding to the N-S joins between the magnets.
OK, so my problem is, when I scan the actual array, using a Redcliffe Magscan, the vector sum flux density shows 13 big lobes of flux corresponding to the centre of each magnet, with very low flux at the joins.
Why are these results so fundamentally different?

Thanks, Alan

 

[Nergus]

Hi bz2005,

Thanks very much for the 3D simulation back-up! A package that expensive has waaay more 'cred' than a free 2D package; however highly thought of!

I'm hoping to learn a lot more about the mechanics of the Magscan, starting next week. It's certainly true that the vector sum peaks are significantly lower than FEMM predicts. I'd thought that was due to a combination of the Magscan only being specified for accuracy over +/-500mT, plus me modelling N52 material and scanning N38. Neither factor has any bearing on the fundamental number and position of flux density peaks.

A couple of experimental magnet arrays in N48 have arrived today, so I'll try to speed-up the point at which we test with nanoparticles.

Alan

 

[bz2005]

Hi Nergus,

Please keep us posted as how your nanoparticles behave above the magnet array. I suppose they will accumulate over the boundaries, but it would be nice to get it confirmed.

Bo