Hi Ok, what happens if you keep the air gun in the exact same position and let it stabilize for an hour with no insulation around the OCXO ?
Bob On Dec 19, 2012, at 7:24 PM, [email protected] wrote: > Hi Bob, et. al., > > this discussion prompted my interest to see how a 10811-600160 unit that we > have sitting here on the bench would react to airflow changes. I had a > thin layer of anti-static shipping material around the unit, and I opened up > one side of that layer and then pushed air into that side. > > The unit is from a 53132A counter, and has the 53132A OCXO PCB with voltage > regulator attached to it, and is being fed from an external stable power > supply. > > Please see the frequency plot attached, I used an air gun to push air onto > the unit for about 60 seconds or so. The unit had quite a large and > immediate change in frequency, up to about 3.5E-011 and then down to -4E-011 > at > which point I captured the image (while it was still drifting negative). I > did not wait until it settled back (will take probably 30 minutes or more I > would guess), but it went quite a bit more negative after I captured the > plot. > > This airflow sensitivity is probably a combination of the circuitry on the > support PCB, the OCXO, and the external power supply. > > The stability before the unit was exposed to the airflow was quite good as > can be seen in the left half of the plot, and I think this illustrates how > adding a bang-bang type airflow to these oscillators can worsen ADEV > performance significantly, albeit we are talking 10's to 100's of parts per > trillion here.. I would much rather see the unit perform as it did initially > in > my test setup without the airflow though. > > bye, > Said > > > > > > > In a message dated 12/16/2012 18:11:02 Pacific Standard Time, [email protected] > writes: > > Hi > > … and what I'm trying to say also comes from the real world... > If you start putting "stuff" on an OCXO, be careful about the case > temperature and how the OCXO is spec'd. A few mm of dead air can make a good > insulator. That can boost the case temp quite a bit. > > Bob > > On Dec 16, 2012, at 9:06 PM, Magnus Danielson <[email protected]> > wrote: > >> On 12/17/2012 02:47 AM, Bob Camp wrote: >>> Hi >>> >>> The gotcha here is that an un-cooled piece of gear will heat up and > cool down as it's work load changes. There is no "magic bullet" that keeps > the temperature constant with zero airflow in a normal design. Yes, I'm old > enough to remember oil cooled computers. Still no constant temperature and > you have turbulence. >> >> I agree that there is no "silver bullet", but my point was that > sometimes you kill one property when you apply a solution to another > problem. I am > very well aware of heating problems and cooling my components, as this is > part of my real world. But rather than isolating the full box, I'm talking > about the TCXO or OCXO. Just putting a small wind-shield over it changes > things a lot at times. >> >> Cheers, >> Magnus >> > > <10811_60160.pdf>_______________________________________________ > 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.
