[time-nuts] Z3805 initial behaviour after power up
sar10538 at gmail.com
Wed Jun 17 05:03:11 EDT 2009
What are you using to produce the graph you attached please?
2009/6/17 Ulrich Bangert <df6jb at ulrich-bangert.de>:
> 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
> 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
> Ortholzer Weg 1
> 27243 Gross Ippener
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