[time-nuts] 10811 crystal orientation

[Said Jackson]

Hello Tom,

this plot looks very similar to our standard double oven units. We  
have our low-g option, which reduces the deviation to about 2-  3E-10  
per g, they work great but do cost more than standard units..  
Coincidentally they also reduce sensitivity to vibration and "tapping"  
by 5x to 10x... I wish we could offer them at the same price, but they  
are very difficult to manufacture. That's why no one uses them by  
default in their product.

Bye, Said



 From iPhone

On Jul 10, 2009, at 15:51, "Tom Van Baak" <tvb at LeapSecond.com> wrote:

>> One is do crystal oscillators change frequency when they
>> are turned. The answer to that is yes. This gravitational
>> acceleration effect is rather huge, parts in ten to the 9th
>> or so, and anyone can see this. This is why you never
>> touch, bump, or move, or rotate a laboratory frequency
>> standard (this includes GPSDO and cesium standards).
>
> And to give you a *picture* instead of just numbers... Here is
> a plot showing frequency changes in an OCXO (this from a
> free-running Thunderbolt GPSDO) over the span of one hour.
> Every 5 minutes or so I rotated the rectangular box on some
> axis by 90 degrees.
>
> <http://www.leapsecond.com/pages/ocxo-2g/TBolt-2g-6axis.gif>
>
> You can see that the sudden frequency jumps due to change
> in g-force on the crystal are about -0.5e-9 to +1.5 e-9, which
> is 100x the normal frequency noise for this oscillator (about
> 2e-11 pk-pk or about 2e-12 adev).
>
> Hopefully this result won't come as a big surprise to anyone; the
> so-called "2g turn-over" spec is common for quality oscillators.
> Again, this is why when you enter the world of precision timing
> at 1e-10 and below you tend not to ever touch your standards.
>
> Now if one of you happened to have a fully-programmable 3-axis
> turntable and a couple of hours you could slowly create a most
> beautiful high-resolution 3D color plot showing the precise shift
> in frequency as a function of axis.
>
> /tvb
>
>
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