[time-nuts] CSAC Project(was CSAC purchase)

gandalfg8 at aol.com gandalfg8 at aol.com
Thu Jan 25 12:39:06 EST 2018


The CSAC spec sheet calls out an aging rate of 0.9 ppb per month as 
“typical”. There is also a temperature spec of 0.4 ppb. If both are correct 
for your sample (*and* aging is linear ) you would be out by roughly 10 ppb
per year. There also is a voltage stability spec that might be impacted depending
on how you manage power. 

Taking the 30 ppb = 1 second number, you are at a 1 second / year rate after 3 years. 
At that point, you have already drifted by a second, if the assumptions are correct. 
This makes a massive assumption that the aging stays at the “typical” rate
for years. It’s a very good guess that it does not. Is it going to be 1/3 or 1/10
of typical over that period? Who knows. 

Bottom line, you are going to be pretty far from 1 second per 100 years with 
a CSAC based wrist watch, if it runs for years (or even for months).  It *will*
do *way* better than a TCXO or OCXO based watch over months or years.
It’s still not perfect. 



 "if it runs for years (or even months)" sounds like an informed comment:-)

When searching for some data recently I came across a report which might be relevant.

"A Second Look at Chip Scale Atomic Clocks for Long Term Precision Timing", written by 
Alan T. Gardner and John A. Collins of the  Woods Hole Oceanographic Institution, details their
experience with a number of earlier and more recent CSAC modules and their findings make
for very interesting reading.

At the time of writing a copy is available here....



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