> The problem which requires to be solved its a small distance measurement
> at high speed (about 15cm/second) in a high EM radiation environement
> (near a few KW generated from 300KHz inductors).

Thinker only :-) :  Capacitance sounds like a good starting point.
If you use an excitation frequency which is not harmonically related to the
other major signals present then filtering may be enough to remove unwanted
signals.

        RM

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