[time-nuts] 10811 crystal orientation

[bg at lysator.liu.se]

Hi Said & Tom,

The below url links some "low-g"-osc papers.

    http://www.freqelec.com/tech_lit.html

Said, did you contemplate adding a cheap 3d-accelerometer and try to teach
your holdover algorithms use the accelerometer measurements in the same
way as your temperature measurements?

--

    Björn

> 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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