[time-nuts] Trimble Tbolt temperature

[Bob kb8tq]

Hi

The temperature chip is there to “learn” the TC of the unit while it is in
lock. If and when the unit goes into holdover that information is used
to compensate the unit. If the environment does not change much when
you are in holdover this may be a benefit. If the HVAC goes when the 
holdover happens …. maybe not so much. 

The DAC and voltage reference  on the E-911 TBolts has a pretty 
substantial temperature coefficient. On top of the wide tune range of the 
OCXO this gives thepart a pretty substantial temperature wander. If holdover 
is part of the “plan” the temperature chip probably is worth having. 

The Nortel GPSDO’s have a very different OCXO in them (normally a double 
oven) with a narrower tuning range The DAC and voltage reference are
done very differently as well. On top of that, the Nortel spec for holdover
was much tighter than the E-911 requirement . Net is that the temperature
chip in the Nortel versions may not be as important, even in holdover.

Yes, way more than you wanted to know …...

Bob

> On Dec 4, 2019, at 2:52 AM, Christophe Huygens <christophe.huygens at kuleuven.be> wrote:
> 
> Thanks all - if of no consequence, case closed.
> 
> On 04/12/19 03:03, Tom Van Baak wrote:
>> Most TBolt measure board temperature to about 1/100th C resolution.
>> This is the correct behavior. Some TBolt report temperatures that seem
>> to step in 1 C increments, or they report a constant -55 C, or they
>> glitch once in a while. These are bugs.
>> 
>> You can replace the DS1620 chip if you want. It's perhaps best to
>> locate the 20-year old version of the chip. There are lots of threads
>> about this in the archive.
>> 
>> The DS1620, working or not, has no effect on the performance of a
>> running TBolt. So I've never bothered replacing any of mine. It may
>> have a slight effect on extended holdover performance. It's a long
>> story and I'm not sure if anyone has actually verified or quantified
>> this.
>> 
>> Here's additional info about the TBolt & DS1620; it's more complex
>> than you think:
>> 
>> "Strange temperature peak"
>> https://lists.febo.com/pipermail/time-nuts_lists.febo.com/2011-May/039188.html
>> 
>> 
>> "Trimble Thunderbolt GPSDO Temperature Sensor Details"
>> http://leapsecond.com/pages/tbolt-1620/
>> 
>> "Dallas state machine glitch"
>> https://www.digitemp.com/docs/ds1820-report.pdf
>> 
>> /tvb
>> 
>> 
>> On 12/3/2019 1:47 AM, Christophe Huygens wrote:
>>> Hi all,
>>> 
>>> I am back on time-nuts after many moons.
>>> 
>>> Lady heather shows constant -55deg C for my Tbolt.
>>> 
>>> all else seems to function fine (is in a constant T environment, sort
>>> of)
>>> 
>>> Any thoughts....
>>> 
>>> br and thanks
>>> 
>>> Xtof
>>> 
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>> 
>> 
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> 
> -- 
> --
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> prof. dr. ir. Christophe Huygens  iMEC-KULeuven-DistriNet
> 
> 
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