Neat work and interesting reading. A few comments:

There is indeed software for calculating field distributions. Unfortunately, I can't find the links. As I recall it's payware, but there may have been a trial or student version.

Your double magnet approach will offer the best results if you keep some distance between the sides of each magnet and the C-shaped shield. When the magnet is too close, the shield "short circuits" a significant amount of the flux and the field distribution in the gap is distorted.

The single magnet approach works best when you use low remanence material for the flux concentrators. It looks like they are made from mild steel washers. The problem is that they magnetize slightly and add hysteresis to the system. If you turn the shaft to the right and then to center you get one voltage out. If you then turn the shaft to the left and back to the same center position you get a slightly different output voltage.

It's nice to see more work done in this area. Hall devices are under utilized by hobbyists.

Last edited by Mike Powell; 08/10/10 04:01 AM.