I finally got around to documenting the sensor coils and the case millwork! It's the small things in life that matter, or that's what I told myself. :)

The coil (rev 1.0). The relevant parameters of the coil are now documented in the source tree of the PyPPM project tarball. This nails down the exact design parameters I used. While you could go to the trouble of fabricating coil forms using a 3D printer, it's easiest to use 2" diameter plumbing PVC from a hardware store. Just close off one end, add a screw cap to the other, and wind the wire between the raised edges of the pipe fittings.

The coil (rev 2.0). My plan to use counter-wound solenoids is finally taking shape. From my estimates, the interaction (during polarization) between the solenoids will be negligible at a 15 cm distance. However, that's only a relevant consideration for the current PPM board, which will have to polarize and observe on both coils in series. Newer versions of the hardware will connect to the coil using a proper three-wire system, which will allow for polarization of a single coil and acquisition through both coils differentially.

The case. While the dimensions of the case cutouts are completely unexciting, they're still progress:

More to come on the hardware designs, including an update on the shim driver circuits!