[time-nuts] Re: hydrogen rich environment and oscillators
Bob Camp
kb8tq at n1k.org
Tue Dec 13 17:09:25 UTC 2022
Hi
As price goes down, so must cost. If not, the outfit goes broke. Working
out just what gets âleft outâ on a $1 TCXO is almost impossible unless
you can go do an audit of the production line at the time the parts are
being made.
Next question would be: Are the parts evacuated before seal? Iâd bet not.
They likely get some sort of inert gas fill and thatâs about it. If so, you
already *have* gas in the package. Thereâs not a lot that a one gas
will do vs another as far as damping the crystal. Also, with a more or less
zero pressure differential, not much He or H is going to work itâs way into
the package. Yes, this *assumes* the parts are crystal based â¦.
Itâs not all that hard to test this out. Get or rig a pressure container that
will take 50 to 100 PSI. Go over to the local gas store and get a small
bottle of He or H. Bomb the parts overnight at 50 to 100 PSI. Pull them
out and see if they still work â¦â¦ If so, you have just done what is likely
the â100 year testâ on the parts. If they donât work, see if you have crushed
the parts ( = smashed the package flat â¦) and try again at a lower
pressure ⦠:)
Bob
> On Dec 13, 2022, at 10:01 AM, Lux, Jim <jim at luxfamily.com> wrote:
>
> On 12/13/22 5:57 AM, Bob Camp wrote:
>> Hi
>>
>> If you have a welded package TCXO, itâs a reasonable guess that it may have gone
>> through the normal âmil specâ leak test. Mil STD-202 method 112 test condition C
>> gives you all sorts of fun information. It also heads off in many directions.
>>
>> As normally done on a crystal oscillator, you put the parts in a pressure vessel for
>> about an hour. Itâs pressurized at around 50 PSI with 10% helium. Yes both the time
>> and pressure are past what method 112 calls out as the minimums.
>>
>> After being soaked like this, they go into a mass spectrometer to look for helium
>> coming back out of the parts.
>>
>> Pretty much any mil spec or space spec welded part would go through that test or
>> something very much like it. Thatâs true regardless of who made the part.
>>
>> The only relevant point here is that if this sort of exposure killed the parts, it would
>> show up and folks would very much know about it.
>>
>> Welded crystals going into precision oscillators get the same sort of leak check or
>> possibly something more in depth. Thereâs no guarantee on this so itâs not quite as
>> much a sure thing as the space or mil oscillators. Still, if this killed crystals you would
>> know about it.
>>
>> Before anybody asks, yes, some parts do leak. I donât remember any of them being
>> non-functional. However, you donât test those parts much. They are headed to the
>> recycle bin.
>>
>> Bob
>
>
> OK. so welded packages (particularly those that are procured for space) aren't likely to leak, they tested, etc. I'm sort of interested, though in COTS cheap oscillators like these tiny $1 Abracon units. (I don't know what they use on Arduinos and RPi, but it's something like this).
>
> https://www.mouser.com/datasheet/2/3/ASEseries-38758.pdf
>
> They're sort of silent on the datasheet about sealing, etc. And at $1.38 each, do they actually leak test them?
>
>
>
>
>
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