[time-nuts] CS reservoir depletion

Bob Camp lists at rtty.us
Fri Jan 14 17:55:52 UTC 2011


There is a lot of data that says crystals "relax" while off power. The older
they are (the older the process) the more likely they are to do so. The net
effect is that they will move much faster on a per day basis than you would
expect them to. They will eventually calm down, but it can take months.
Things like mounting stress (TCE miss match), and thermally introduced
changes in junk equilibrium are the two most commonly claimed sources. 

One example is the GR standard I have in the basement. It's now down to a
sub 1.0x10^-11 per day sort of aging rate. When I fired it up, it was moving
more than 1.0x10^-8 per day.

As with any rule like this, there will indeed be parts that break the rule.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of J. Forster
Sent: Friday, January 14, 2011 12:45 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] CS reservoir depletion

Bob, is there any indication in you have to "run it for a while" depends
on how long it has been off?

Does a crystal oscillator that has been off for 50 years, take longer than
one that has been off for a week?

I ask because the 1818.18 Hz crystal in a LORAN-A Test Set I picked up is
currently running at about 1818.48 Hz. It's been off since about 1945.




 That assumes it was on power for a good part of
> it's
> life. If it's been on the shelf for 20 years, you may need to run it for a
> while ...
> Bob

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