[time-nuts] Helium and MEMS oscillators don;t mix well

Bob kb8tq kb8tq at n1k.org
Thu Nov 1 15:20:07 EDT 2018


Hi

Now, getting back to the original issue. MEMS oscillators of some types have
really tiny structures in them. They mount them as close to being in “free space”
as they can. The idea is no different than a crystal. A properly shape lump running 
in free space has higher Q. Higher Q is normally a good thing in an oscillator.

It’s not a great leap to guess that there may be magnetic materials in a structure 
like that. If so, a giant magnetic field could put some force on the mounting structure.
Put to much force (or to quick a “snap” in that force) and there goes the structure into 
really tiny pieces …..

Yes, there are a lot of other EMI possibilities. Last time I checked, things like phones 
and watches were not on the list of what you took with you for an MRI ….

Bob

> On Nov 1, 2018, at 3:05 PM, David Witten <wittend at wwrinc.com> wrote:
> 
> Please pardon my usual incompetence posting to mailing lists...
> 
> 2nd MRI center reports problems with Apple devices
> <https://www.auntminnie.com/index.aspx?sec=sup&sub=mri&pag=dis&ItemID=123411>
> 
> Aunt Minnie is a newsletter/site targeting clinical radiologists and
> technical staff.
> 
> Dave
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