40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
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
elog_EOMServoNotchTune.pdf
Attachment 2: 20170904_FSSTFs_tuningEOMServoNotch.zip  871 kB
ELOG V3.1.3-