I have an app with 1% precision inductances (RM6 adjusted pot cores) and specified tempco.
Now the customer wants all that potted.
I never had experience with this, but I recall having seen reported here some bad stories about potting cores, IIRC something about potting preventing core volume magnetostriction, hence modifying its permeability...
Any story, good or bad, about this?
-- Thanks, Fred.
Do not use a hard set potting compound. ONLY use RTV, or polyurethane or the like, OR you must vacuum impregnate the finished inductors with varnish to keep the potting medium from getting into places within the assembly that cause issues like that you describe. Impregnation is always a good thing anyway to lock such a device within a known window of operation.
Well, the cores are already varnished (vacuum impregnated). But I'm still anticipating some issues. Some grossly out of tolerance measurements on a complementary product make me cautious. Unfortunately I'm not allowed to "open" it and I have no info about the internals.
I've once seen mentioned use of some soft "strain shielding" material before potting.
Still looking for good stories to convince the customer to spare a few days investigating this...
-- Thanks, Fred.
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