[time-nuts] OCXO sensitive to gravity

Robert Darlington rdarlington at gmail.com
Sat Aug 15 21:40:00 UTC 2009


I don't know.  I'm just the lab tech!   I cater to national labs, in
particular LANL which is right down the street from me.  I've been involved
with the guy that developed SFAI (swept frequency acoustic interferometry).
We use this technique to fingerprint and characterize various substances
-anything from oil/water cut in the petrolieum industry to nerve agents in
Iraqi shells (original design purpose), to determining what liquid is in the
bottle packed in your carry on luggage.  I'm familliar with all of the
measurment processes and have acted as the hands of the scientists on more
than one occasion but simply don't know enough to know if this level of
precision matters or not.

-Bob

On Sat, Aug 15, 2009 at 2:29 PM, WB6BNQ <wb6bnq at cox.net> wrote:

> Hi Bob,
>
> Why do they have to be so precise ?  And what are they being used for ?
>
> Bill....WB6BNQ
>
> Robert Darlington wrote:
>
> > One of my side jobs is to produce better than state of the art ultrasound
> > transducers.  That being said, there is nothing particularly better about
> > mine other than when I say it's a 1MHz transducer, I really mean
> 1.00000Mhz,
> > not 980kHz, not 1.2Mhz.  The way I achieve this is to lay down gold, a
> few
> > atoms at a time, and track a resonance peak (network analyzer and some
> > simple code in VB of all things).  We actually drive the transducer as we
> > sputter coat the gold on top and can see the resonance point shift, real
> > time.  Cool stuff.  They use a similar process in industry but they're
> > looking at one data point in a vacuum chamber full of transducers.  I'm
> > looking at every single one.
> >
> > -Bob
> >
> > On Sat, Aug 15, 2009 at 1:56 PM, J. Forster <jfor at quik.com> wrote:
> >
> > > > And billions of accelerometers (from air bag sensors to Wii game
> > > > controllers to the iPod touch and iPhone) have been produced in
> > > > the past decade. Google words like MEMS Quartz Accelerometer.
> > > > Also for Quartz Rate Sensor QRS.
> > >
> > > I'm not so sure they use quartz. The ones I've seen are micromachined
> from
> > > silicon and have both the beam and electronics on the same chip.
> > >
> > > > I've seen quartz resonators used to measure to impurities in the
> > > > making of semiconductor wafers -- they measure the change in
> > > > frequency of an exposed quartz resonator as atoms fall on the
> > > > exposed crystal and change its frequency. Note that a 1 mm
> > > > quartz crystal is only about a million molecules thick. So adding
> > > > a layer of only 1 atom will change the frequency in the ppm range.
> > > > We can measure a thousand or million times better than that.
> > >
> > > Not impurities, but the deposition of metalizing films, etc.
> > >
> > > > As you feel your heart beat, google for Quartz Pressure Sensor
> > >
> > > Again, I think these are semiconductor sensors.
> > >
> > > > Quartz is really quite amazing. It's almost a shame to shield it
> > > > from everything so all they have left to do is try to measure time!
> > >
> > > LoL. The crystals ARE pretty nice.
> > >
> > > Best,
> > > -John
> > > >
> > > > One other note: rubidium vapor frequency standards are much
> > > > more sensitive to magnetic fields than cesium beam standards.
> > > > I've heard that military sub-hunting sea planes use deliberately
> > > > un-shielded rubidium clocks to detect hidden submarines. Google
> > > > for words like Rubidium Magnetometer ASW P-3 Zeeman
> > > >
> > > > As always, one man's error is another man's signal...
> > > >
> > > > /tvb
> > > > http://www.LeapSecond.com
> > >
> > >
> > >
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