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Entry  Thu Aug 31 20:24:38 2017, Craig, awade, DailyProgress, FSS, OLGs from OUT2/EXC measurements 20170831_195251_OLG_from_North_OUT2_over_EXC_29-08-2017_221042_Merged.pdf20170831_195401_OLG_from_South_OUT2_over_EXC_30-08-2017_002657_Merged.pdf20170831_200715_OLG_from_South_OUT2_over_EXC_30-08-2017_002657.tar.gz20170831_200850_OLG_from_North_OUT2_over_EXC_29-08-2017_221042.tar.gz
    Reply  Fri Sep 1 16:58:10 2017, rana, DailyProgress, FSS, OLGs from OUT2/EXC measurements 
       Reply  Tue Sep 5 20:38:20 2017, awade, DailyProgress, FSS, Tuning the PC servo notch elog_EOMServoNotchTune.pdf20170904_FSSTFs_tuningEOMServoNotch.zip
Message ID: 1896     Entry time: Tue Sep 5 20:38:20 2017     In reply to: 1890
Author: awade 
Type: DailyProgress 
Category: FSS 
Subject: Tuning the PC servo notch 

I went to the lab yesterday and tuned C13 on the EOM Path servo stage notch (see schematics in DCC-D040105).  I took a before and after supression function in the common path to show the change but it turns out I had not hooked the excitation up, so the data are no good.  

The notch was a little off the EOM resonance.  It was super sensitive and the capacitance of the screwdriver touching the capacitor also affected the notch frequency.  Through trial and error I think I got it centered but its a bit hard to quantify how much better it is.  I took a out1/out2 type transfer function while I was doing the tuning (attached below). It was imposible to get the notch to exactly overlap and cancel the EOM peak.  I guess the idea is to mostly cancel it and not compleatly null over that band. As there is no driving excitation in this measurement I'm not sure how much I trust the abolute magnitude of the supression.  However, it is centered now, we'll see once we re take the loop supression function and unrap the open loop gain from that.


Data is stored in ligo git repo ctn_labdata under data/20170904_FSSTFs_tuningEOMServoNotch. Zip of data and plotting scripts attached in zip below.

Attachment 1: elog_EOMServoNotchTune.pdf  50 kB  | Hide | Hide all
Attachment 2: 20170904_FSSTFs_tuningEOMServoNotch.zip  871 kB
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