[time-nuts] OCXO sensitive to gravity

WB6BNQ wb6bnq at cox.net
Sat Aug 15 20:29:34 UTC 2009


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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