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Entry  Thu Sep 18 02:42:28 2014, Jenne, Update, LSC, AO path partly engaged Zoom_TRXTRY4_EngagingAO_1095059162.png0020.pdf
    Reply  Thu Sep 18 17:44:55 2014, Jenne, Update, LSC, Old AO cable pulled 
       Reply  Tue Sep 30 17:26:18 2014, ericq, Update, LSC, New AO cable in place 
    Reply  Fri Sep 19 04:05:05 2014, ericq, Update, LSC, AO path partly engaged TFSR785_19-09-2014_020555.pdfTFSR785_19-09-2014_033920.pdf
       Reply  Fri Sep 19 13:12:07 2014, Jenne, Update, LSC, AO path glitches 
Message ID: 10521     Entry time: Fri Sep 19 13:12:07 2014     In reply to: 10520
Author: Jenne 
Type: Update 
Category: LSC 
Subject: AO path glitches 


Discontinuities / glitches could be seen in the CM board fast output when MC board gains were changed, which isn't so nice. Incidentally, I notice now that each lock loss corresponded to a step of AO gain on the CM board.

Back in May I looked at all the glitches that happen when we change the AO gain slider on the CM board - see elog 9938.   I wonder if the MC IN2 gain slider has the same issues.  I think I'll look at this this afternoon. Maybe we can set the CM board gain someplace, and just use the MC IN2 slider (if it's not as glitchy) for the delicate part where we're just about to cross unity, and then later we can again use the CM board's AO gain.

EDIT:  Yes, the glitches on the CM board AO path are *much* bigger, and more frequent.  Interestingly, the biggest glitches were every 4 dB.  When I went from -29 to -28, again from -25 to -24, -21 to -20, etc.  I saw the largest glitches on the MC IN2 slider going -29 to -28 and -17 to -16, but if there were small glitches at other transitions, they didn't hit my trigger levels.  I think next time I try engaging the AO path I'll try to do the delicate stuff by upping the MC IN2 gain rather than the CM board AO gain.

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