[time-nuts] Thunderbolt performance vs temperature sensor

SAIDJACK at aol.com SAIDJACK at aol.com
Sat Mar 7 03:35:30 UTC 2009

Hi there,
Would you have the EFC plots while in holdover for us?
You can try to place the unit into your refrigerator. That will drop it  down 
to 3C or so from ambient. That will give you enough of a change so that you  
can see how the EFC changes with the two sensors.. It will also give you a 
good  idea how good the OCXO itself can handle thermal shocks.
BTW: the drift you described is quite high, it definitely busts the CDMA  
spec in both cases (CDMA: 7us/Day or so). But I am not surprised by this if they  
use the Dallas chip for temp compensation of the OCXO.
A good GPSDO (with double oven) should not drift more than 1us per day  
typically in holdover after one week of continuous operation.
In a message dated 3/6/2009 16:04:32 Pacific Standard Time,  
holrum at hotmail.com writes:

Hello  Said,

The Tbolt that I used for the test was well aged (several months  of 
operation) and stable prior to the tests.  It was only powered down  for the 10 
minutes or so that it took to swap out the old sensor.

I  tried to choose data sets that were fairly comparable temperature wise.   
I also chose the basic measurement interval to be 1 hour so that temperature  
would not be changing much over the hour.  I am fairly confident that the  
results reflect changes due to the temperature sensor.

I wanted to make  the measurement PPS drift / degree C change / hour but the 
later model (low  res) temp sensor chip would seldom produce a recordable 
change in temperature  over a one hour period.

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