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" <t...@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 >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.