[time-nuts] OCXO sensitive to gravity

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Thu Aug 13 23:00:49 UTC 2009


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Rick Karlquist
> Sent: Thursday, August 13, 2009 3:35 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] OCXO sensitive to gravity
> 
> Tom Duckworth wrote:
> > The orientation change is due more to the earth's magnetic flux
> effect on
> > the oscillator, and less so from gravity.
> >
> > Tom
> > Tom Duckworth
> > tomduck at comcast.net
> 
> Sorry, this is simply incorrect.  Magnetic flux from the
> earth has no effect on quartz oscillators.  There is no
> mechanism there.  Acceleration definitely affects quartz.
> 
> 

Hmm. We're investigating just this at work, in connection with things destined to orbit Jupiter, where we expect to see a periodically varying flux as the spacecraft spins.  The quartz is insensitive, but the mounting isn't necessarily insensitive to magnetic fields, especially if any magnetic materials (i.e. Kovar seems to be of interest) are used.

If you have any circuits sensitive to DC offsets, then a varying magnetic field can cause problems (e.g. the VCO input in a PLL).

I suppose it depends on "how good" the oscillator is expected to be...



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