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Entry  Mon Dec 5 10:39:16 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue 
    Reply  Tue Dec 6 09:02:17 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue 
       Reply  Tue Dec 6 10:38:19 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue Screenshot.pnggps_time_offset.png
          Reply  Tue Dec 6 11:22:58 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue Screenshot-3.png
             Reply  Tue Dec 6 16:55:51 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue Screenshot.png
                Reply  Wed Dec 7 08:14:05 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue Screenshot-1.png
                   Reply  Wed Dec 7 16:27:11 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue 
                      Reply  Thu Dec 8 09:26:10 2016, Gabriele, Electronics, Configuration, Trying to debug GPS time issue figure_1.pngfigure_1.png
Message ID: 229     Entry time: Tue Dec 6 11:22:58 2016     In reply to: 228     Reply to this: 231
Author: Gabriele 
Type: Electronics 
Category: Configuration 
Subject: Trying to debug GPS time issue 

I swapped the SR signal generator with an Agilent 33210A. Shut down and restarted the cymac3. Now the command line GPS and the IOP model GPS are aligned within one second. Let's see if it stays this way.

 

Quote:

UPDATE:

Now the time difference is about 30 seconds. It seems that the real time model is about 29 seconds advanced with respect to the GPS time one gets from a python script command running on the cymac3

The GPS time I get from python is the same I get from a shell script on the workstation or on the cymac3. I checked that it is also consistent with the GPS time on cymac2.

I moved the picomotors at precise times and looked at the data in the frames. Indeed the data has the wrong time stamp.

Quote:

Things seems to be worse now. This morning I injected noise at GPS 1165078533 (real time, as obtained from the python command line, and consistent with what displayed in the MEDM screen) and found the injection in the data at GPS 1165078555, so 22 seconds later...

Quote:

For a long time I had problems with the GPS time in frames being different from the real one.

This morning I rebooted the cymac3 and swapped the function generator with a new one.

I tested the GPS time in frames by switching on teh ESD noise at a given GPS time and checking the frames. The times are aligned.

I'll have to wait and see if this remains stable over time (in the past i saw an acculation of few seconds per day)

 

EDIT: I checked the two SR DS345 one against the other. Indeed, when bpth set to generate 65536 Hz, there is a continuos drift in the relative phase, accounting for one cycle over about 3.9 seconds. This would sum up to one second over ~256000 seconds, or about 3.5 days. It seems more or less comparable with the amount of GPS time mis-syncronization I saw. I'll have to wait a few days to see if the new clock is stable.

 

 

 

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