Great plots guys! Looking at these results I think my original claim still holds: ADEV goes up when a fan is involved versus no fan, even on a double oven 10811..
Clearly visible on the 10811, maybe not so much on the MV89 but that unit seems to have frequency moves into the xE-010 region on Marks plot so maybe the effect is just a bit hidden? Bye, Said Sent from my iPad On Dec 21, 2012, at 5:44 AM, Volker Esper <[email protected]> wrote: > ...and the picture of the experiment... > > >> The picture enclosed can give you a first impression. What we see is >> the difference time between the GPS signal and the OCXO (blue) >> ("PPS-TI"), which is an HP 10811. In red we can see the EFC. The total >> span is 24 h. >> >> Before I applied the fan, the noise was at a maximum of about +/- 20 ns. >> Some hours after starting the fan the noise is much greater. That should >> have a significant impact on the ADEV. >> >> I don't put the ADEV curves here, I make up for it when the EFC >> compensation is completely out of the scope, that will be in about 12 >> hours. I don't have the ADEV at 1 s, but the ADEV at 10 s has been >> almost constant. The ADEV at about 1000 s has a nasty bump now. >> >> IMHO that fits to the physical facts: the airflow will surely not affect >> the 10 s ADEV since the OCXO tries its best to isolate the oscillator >> from short time temperature influences. However, the turbulent air flow >> that I applied will influence the longer time ADEV. >> >> Have a nice solstice >> >> Volker >> >> >> >> >> Am 21.12.2012 12:44, schrieb Volker Esper: >>> >>> Yes, I made such a setup, it's now running 22 hours. I'll post the >>> results in two hours or so (if nothing evil happens to the earth, >>> meanwhile). >>> >>> Volker >>> >>> >>> Am 21.12.2012 03:35, schrieb [email protected]: >>>> Wish I had more time to play with this setup. >>>> >>>> How about fellow time nuts spend some time and present similar test >>>> data on >>>> their OCXO's to compare? >>>> >>>> I was interested in the 1s to 100s ADEV, and my runs were from 8 >>>> minutes to >>>> 20 minutes, certainly enough time to capture data for 1s to 100s ADEV >>>> measurements.. >>>> >>>> bye, >>>> Said >>>> >>>> >>>> In a message dated 12/20/2012 14:17:59 Pacific Standard Time, >>>> [email protected] writes: >>>> >>>> On 12/20/2012 01:34 PM, Bob Camp wrote: >>>>> Hi >>>>> >>>>> Temperature transients are not a good thing for an OCXO. If you >>>> deliberately use the fan to create a transient, then yes the OCXO will >>>> not be >>>> happy. The question it - what happens after the transient has settled >>>> out? The >>>> plot you have still looks a lot like a step function. >>>> >>>> I agree. Temperature steps stresses the OCXO oven loop and easily >>>> creates a gradient over the crystal. As the oven loop tracks in, the >>>> frequency returns to around normal. The trouble with forced air over a >>>> crystal is that the metal shield couples very well and acts like a heat >>>> sink. A think plastic cover over it and forced convection doesn't have >>>> the same effect. There is even being used by at least one vendor. Works >>>> very well for the extra cents of manufacturing cost. >>>> >>>> The HP10811 is recommended to be put in a airflow-quiet corner of the >>>> world. Look at it's mounting in the HP5370A/B for instance. >>>> >>>> Cheers, >>>> Magnus >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. > > <DSCF1758_bb.jpg> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
