That is interestng and brings a question that I should be able to answer but have been too busy (or lazy...) to try...
The HP 5370 has a noisy fan, and an HP 10811 in the same box. Has anyone been curious enough to measure the effect of fan vibration on the oscillator and p-p noise on TI measurements? Didier > -----Original Message----- > From: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak > Sent: Friday, July 10, 2009 5:51 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] 10811 crystal orientation > > > 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.