Not sure to understand your setup, as I don't know that kind of equipment.
Copper clad may be there to create eddy currents.
If the magnetic arrangement is such that a substantially constant magnetic induction traverses at right angles the copper surface (that should face the gap between the magnetic field and the ferromagnetic 416 steel ring), then the result would be that, by forcing one of the two parts to rotate, the other one is driven into rotation also. Now if the driven part is retained by a spring, its angle of rotation will be related to the rotational speed of the facing element. Or, if it is free to rotate but with some friction, it will rotate at a different speed, and the speed difference would also depend on the driving speed.
As someone noted above, copper thickness seems to be so small, that it is difficult to imagine it is there for conducting eddy currents: however copper conductivity is very high, so, if your equipment is just a small unit, then it might be as described above.
The characteristic of such a sensor would critically depend on copper quality and thickness, on the ferromagnetic properties of the 416 ring and of course on the strength of the magnetic field. The ring should be strongly attracted by a permanent magnet and have no residual magnetism when the magnet is removed.
prex
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