[time-nuts] Thermal impact on OCXO
tshoppa at gmail.com
Wed Nov 16 15:33:03 EST 2016
I've broadly understood the aging in the first days to month as being
dominated by "bake-out". It's well fit with a logarithmic curve but the
effect is so large in the first weeks that it hides the true long term
aging (which could well have a different direction).
On Wed, Nov 16, 2016 at 2:41 PM, Lars Walenius <lars.walenius at hotmail.com>
> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch
> type without EFC marked OFC MC834X4-009W with date code 97. Probably it was
> from some base station testing and it had been sitting in my shelf since
> 98. The OCXO were battery backed but at two occasions (2004 and 2007) we
> had power fails that drained the battery as can be seen in the graph.
> Just out of curiosity I yesterday put just the first thirty days (like in
> the pdf mentioned below) and let Excel calculate the logarithmic function.
> If I extrapolate that to 10 years it seems that the drift would be
> 6E-13/day but as can be seen in the aging graph it was more like ten times
> Some days ago I started the OCXO again after it had been on the shelf for
> more than 4 years. Enclosed is a graph for the first 7 days. After six and
> half days it seems to be a jump of about 1.5E-10 and as I have no
> indication of anything else I believe it is from the OCXO.
> >On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe <scott.j.stobbe at gmail.com>
> > Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> > i/1987papers/Vol%2019_16.pdf; the first that showed up on a google
> > Year Aging [PPB] dF/dt [PPT/Day]
> > 1 180.51 63.884
> > 2 196.65 31.93
> > 5 218 12.769
> > 9 231.69 7.0934
> > 10 234.15 6.384
> > 25 255.5 2.5535
> > If you have a set of coefficients you believe to be representative of
> > OCXO, we can give those a go.
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