[time-nuts] Microphonic Inductor?

Poul-Henning Kamp phk at phk.freebsd.dk
Tue Apr 13 13:57:22 EDT 2010

In message <OF2E427F16.3B191983-ON85257704.0060021C-85257704.00603EAF at mck.us.ra
y.com>, Joseph M Gwinn writes:

>> If anyone knows a good inductor-series (leaded or smt) that is 
>> known-insensitive to vibration please let us know!
>Air wound coil potted in wax.  Or soft epoxy.  You can make your own, if 
>it comes to that.

Be aware that all non-closed coils are microfonic relative to the
earths magnetic field, and there is nothing you you can do about
it, but a closed design (toroid) or a mu-metal shield.

This is more pronounced for cored coils than air-coils, because all
core materials has magnetic hysteresis.

The effect is usually ignored, but I wouldn't be surprised if it
showed up for time-nuts...


Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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