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Entry  Fri Feb 10 02:35:29 2012, kiwamu, Update, IOO, crazy ground motion MCunlock.png
    Reply  Fri Feb 10 11:01:31 2012, steve, Update, IOO, crazy ground motion seism1davg.png
       Reply  Fri Feb 10 11:46:44 2012, steve, Update, IOO, seismic noise back to normal seism4h.pngseis60s.pngoneday.png
          Reply  Fri Feb 10 15:47:38 2012, rana, Update, PEM, seismic noise back to normal 
             Reply  Fri Feb 10 15:52:35 2012, Jenne, Update, PEM, seismic BLRMS loud too 
                Reply  Fri Feb 10 23:58:30 2012, rana, Update, PEM, seismic BLRMS loud too 
                   Reply  Mon Feb 13 11:30:51 2012, Jenne, Update, PEM, seismic BLRMS loud too 
                      Reply  Mon Feb 13 12:02:17 2012, Koji, Update, PEM, seismic BLRMS loud too 
    Reply  Fri Feb 10 23:19:09 2012, kiwamu, Update, IOO, cross talk causing fake seimometer signals 
Message ID: 6274     Entry time: Fri Feb 10 23:19:09 2012     In reply to: 6266
Author: kiwamu 
Type: Update 
Category: IOO 
Subject: cross talk causing fake seimometer signals 

[ Koji / Kiwamu ]

The frequent unlock of the MC are most likely unrelated to ground motion.

Although the reason why MC became unstable is still unclear.

 

 

There are two facts which suggest that the ground motion and the MC unlock are unrelated :

(1) It turned out that the seismometer signals (C1:PEM-SEIS-STS_AAA ) have a big cross talk with the MC locking signals.

    For example, when we intentionally unlocked the MC, the seismometer simultaneously showed a step-shaped signals, which looked quite similar to what we have observed.

    I guess there could be some kind of electrical cross talk happening between some MC locking signals and the seismometer channels.

    So we should not trust the signals from the STS seismometers. This needs a further investigation.

(2) We looked at the OSEM and oplev signals of some other suspended optics, and didn't find any corresponding fluctuations.

    The suspensions we checked are ETMX, ETMY, ITMX and MC1.

     None of them showed an obvious sign of the active ground motions in the past 24 hours or so.

Quote from #6266

It seems that somehow the seismic noise became louder from about 1:00 AM.

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