[time-nuts] Z3805A cooling requirements?

Said Jackson saidjack at aol.com
Fri Dec 21 17:27:29 UTC 2012


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 <ailer2 at t-online.de> 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 SAIDJACK at aol.com:
>>>> 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,
>>>> magnus at rubidium.dyndns.org 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
>>>> 
>>>> 
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>>> 
>>> 
>>> 
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