[time-nuts] Tbolt temperature sensor

gsteinba52 at aol.com gsteinba52 at aol.com
Thu Feb 5 20:05:50 UTC 2009


Why the doubt? 
Couldn't this just be one input to the Kalman filter? Does the external 
electronics package require the same temperature regulation as the OCXO?
Why not put a cold pack on the DS chip and see if the OXCO output swings as 
wildly as you expect (I think it would be irresponsibly poor design to control 
the OXCO outside of the crystal component).
Perhaps the early units had microdegree resolution for ambient air, but that 
doesn't mean the application *requires* microdegree resolution.

Jerry





Message: 6
Date: Thu, 5 Feb 2009 18:44:08 +0000
From: Mark Sims <holrum at hotmail.com>
Subject: [time-nuts] Tbolt temperature sensor
To: <time-nuts at febo.com>
Message-ID: <BLU125-W41A5B9F9F57936E392BF0ECEC00 at phx.gbl>
Content-Type: text/plain; charset="Windows-1252"


I doubt the temperature sensor is just used for environmental monitoring.  If it 
was,  they would most likely have just used the basic 0.5C resolution reading 
and have been done with it.    Instead,  they do the high res read routine and 
then feed that into a filter to get very smooth high resolution (microdegree 
scale) values.

The whole purpose of a GPSDO with an expensive double oven OCXO is to provide 
extremely high quality holdover performance when GPS signals go away.  To 
achieve this level of performance one needs to compensate for the affects of 
temperature on the parts of the system outside the oven.  0.5C resolution is not 
up to the task of maintaining parts per trillion accuracy.   There does not 
appear to be any other temperature sensor in the Tbolt.



------------
Isn't it likely that a temperature sensor adjacent to the RS232 connector  is 
just going to monitor unit temperature for environmental  purposes, perhaps, 
for example, to give the option for flagging up an  overheating situation, in 
which case surely 0.5C resolution is more than  adequate and the "clunkiness" 
isn't really an issue?




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