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From: Fred Bloggs
User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0
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Subject: Re: Side effects of potting compound !
Date: Sat, 02 Nov 2002 17:30:05 GMT
NNTP-Posting-Date: Sat, 02 Nov 2002 09:30:05 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
> For anyone interested here is what I have found following various combinations
> of the potting experiments regarding the multiturn trimmer (circular track with
> worm drive).
> Potted in epoxy - affected trimmer position during curing.
> Potted in polyeurethane - affected the trimmer position during curing.
> Preset entirely covered in silicon then potted in polyeurethane. No effect on
> trimmer position.
> Conformal coated then potted in epoxy - affected the trimmer position.
> Conformal coated then potted in polyeurethane - affected the trimmer position.
> Grub screw superglued then potted in either epoxy or polyeurethane - affected
> the trimmer position.
> Go figure !
Your 6% error after curing is, not quite, but very close to the
standard wiper non-linearity specifications. It may be that you have
luckily discovered the kind of variation possible across fielded product
subjected to random shocks, temperature cycling and so forth. You may
not be out of the woods yet.
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