[time-nuts] 10811 crystal orientation

[Didier]

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-bounces at febo.com 
> [mailto:time-nuts-bounces at 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 at febo.com To unsubscribe, 
> go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.