I think fundamentally the operation of that 100A coil is the same as in what I have in mind, except I'm trying to make use of the coercive magnetization to make a sort of "pseudo"-differential measurement of low current values (in order of a couple mA DC).
Basically go one way into saturation, then the other way, and see where the current hits the "wall" that coincides with the Hc point. This wall will move in opposite directions when there's another source of DC flux in the core, making measurement possible.
While simulation works great, while waiting for hardware, I'm trying to see all potential real world issues.
One thing I'm having a hard time reconciling is the ridiculous change of Hc (Coercive force) with frequency. (Example attached). This means that the location of the "HC wall" shifts with frequency, but I can't visualize how that looks like when one applies some field to the core.
What does this really mean? To me, the coercive force is just how much field you need to create in opposite direction to reset the magnetization of material once it hit saturation one way. Why would frequency affect that? Are they talking about a simple sinusoidal field? What happens if the field is close to a square wave? Does that mean the simulation is woefully incorrect since it implies a constant Hc, which is actually 10s or 100s of times higher at high frequency (e.g. at the square wave edges)?
This doesn't seem trivial, but I wonder if it's possible to simulate
even more arbitrary cores where the BH curve itself shifts with frequency (becomes much wider at higher frequencies), as it does in real life.