[time-nuts] Tbolt temperature sensor

[Bruce Griffiths]

Mark Sims wrote:
> 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?
>   
Mark

Unless there is sufficient noise or dither merely filtering/averaging a
large number of temperature readings will not increase the resolution to
below 1lsb.
Either internal noise or temperature fluctuations with an amplitude of
at least 1 lsb or so are necessary.


Bruce