[time-nuts] Z3805 initial behaviour after power up

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jun 17 06:39:22 EDT 2009


Steve Rooke wrote:
> Ulrich,
>
> I must have lost the plot here but I thought that was only for HPIB
> data. How are you collecting the data?
>
> 73,
> Steve
>
> 2009/6/17 Ulrich Bangert <df6jb at ulrich-bangert.de>:
>   
>> Steve,
>>
>> my PLOTTER utility. I thought you did already try it out?
>>
>> 73s Ulrich, DF6JB
>>
>>     
>>> -----Ursprungliche Nachricht-----
>>> Von: time-nuts-bounces at febo.com
>>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Steve Rooke
>>> Gesendet: Mittwoch, 17. Juni 2009 11:03
>>> An: Discussion of precise time and frequency measurement
>>> Betreff: Re: [time-nuts] Z3805 initial behaviour after power up
>>>
>>>
>>> Ulrich,
>>>
>>> What are you using to produce the graph you attached please?
>>>
>>> 73,
>>> Steve
>>>
>>> 2009/6/17 Ulrich Bangert <df6jb at ulrich-bangert.de>:
>>>       
>>>> Gents,
>>>>
>>>> yesterday I received the Z3805 that I had bought from
>>>>         
>>> fluke.I on eBay
>>>       
>>>> and immediately put it to work. I recorded the EFC value as well as
>>>> the PPS TI value over about 20 hours. Attached is the graph of thes
>>>> two values.
>>>>
>>>> I interprete this graph in this way:
>>>>
>>>> 1) Immediately after power up (perhaps up to the end of the site
>>>> survey) the regulation loop seems to work with a very short time
>>>> constant which is able to bring the PPS TI close to zero
>>>>         
>>> although the
>>>       
>>>> OCXO has lots of drift at this time.
>>>>
>>>> 2) Then the loop time constant seems to switch to a
>>>>         
>>> significant higher
>>>       
>>>> value which does not keep up with the oscillator's drift,
>>>>         
>>> which leads
>>>       
>>>> to the negative excursion of nearly 500 ns.
>>>>
>>>> 3) This seems to be too much for the regulation which leads to
>>>> switching back to the short time constant and to bring the
>>>>         
>>> PPS TI back
>>>       
>>>> to near zero and to return to the longer time constant again...
>>>>
>>>> 4) ...which lets the procedure repeat again and again:
>>>>         
>>> Drift to -500
>>>       
>>>> ns and pullback.
>>>>
>>>> 5) Note that I thought it was a kind of malfunction and send a
>>>> :system:preset command to the device after the last negative PPS TI
>>>> spike. The result was, that the total procedure repeated: About 2
>>>> hours of PPS TI close to zero then again the drift and pullback
>>>> procedure however with a reduced drift rate.
>>>>
>>>> 6) After 11 hours or so the regulation loop's time constant
>>>>         
>>> seems to
>>>       
>>>> match the OCXO's drift and a "real" lock of the pll seems to take
>>>> place. (The lock led had been on already hours ago...)
>>>>
>>>> Since I do not have an manual for the Z3805: Can any of you Z3801
>>>> owners second this behaviour to be normal or would you
>>>>         
>>> think that it
>>>       
>>>> is kind of special for the Z3805 or even a real malfunction (in the
>>>> sense that the OCXO's drift is above the specs in the beginning)?
>>>>
>>>> Best regards
>>>> Ulrich Bangert
>>>>
>>>> Ulrich Bangert
>>>> www.ulrich-bangert.de
>>>> Ortholzer Weg 1
>>>> 27243 Gross Ippener
>>>>
>>>> _______________________________________________
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>>>> and follow the instructions there.
>>>>
>>>>         
>>>
>>> --
>>> Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
>>> A man with one clock knows what time it is;
>>> A man with two clocks is never quite sure.
>>>
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>>>       
>> _______________________________________________
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>> and follow the instructions there.
>>
>>     
>
>
>
>   
Steve

You're confusing Ulrich's PLOTTER program with his EZGPIB program (which
can also communicate with RS232 devices like GPSDOs).
Once the data has been logged using EZGPIB, then Plotter can be used to
plot/analyse the stored results.

Bruce





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