[time-nuts] Trimble Tbolt temperature

Wed Dec 4 21:01:17 UTC 2019

Azelio,

Grab a copy of the TBolt user manual; google ThunderBoltBook2003.pdf

Section 5.1.2 (Kalman Filtering) on page 5-4 (PDF page 48) says:

----

Kalman filtering is a technique that improves the performance of a GPS 
disciplined clock when GPS drops out. This state is called holdover. 
During holdover the clock relies solely on the oscillator.

Oscillator performance is subject to two basic effects. First, changes 
in environmental temperature can cause the oscillator to speed up to 
slow down. Second, the oscillator has a natural tendency to drift over 
time. This is called aging.

Both temperature and aging can be mathematically predicted. However, the 
characteristics vary from crystal to crystal. The Kalman filtering 
monitors the unique oscillator performance over time and temperature and 
records this behavior.

Then when the clock goes into holdover this filtering corrects for these 
effects producing a more accurate clock. The longer a clock has to 
’train’ the better the Kalman filtering performance will be. 24 hours is 
considered the minimum necessary for good performance.

----

/tvb

On 12/4/2019 7:57 AM, Azelio Boriani wrote:
> 'The temperature chip is there to “learn” the TC of the unit while it
> is in lock.'
> I think this is news for the group: as of my knowledge, we don't know
> if the 1620 has an active role in the TBolt other than measuring
> temperature for the TSIP output.
>
> On Wed, Dec 4, 2019 at 4:04 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>> 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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