[time-nuts] OCXO sensitive to gravity

[J. Forster]

> 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