[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.
bye,
Said
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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