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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: 1888     Entry time: Thu Aug 31 20:24:38 2017     Reply to this: 1890
Author: Craig, awade 
Type: DailyProgress 
Category: FSS 
Subject: OLGs from OUT2/EXC measurements 

We have (finally) gotten appropriate FSS OLGs for both paths.

I wrote a script netgpibdata/takeManyMeasurements.py which does exactly what it says it does.  It takes one .yml file and runs it as many times as you want.  In this way we got overnight measurements of OUT2/EXC.

Then, today I took TFs through OUT2/EXC with the loop open.  I will call these measurements Excitation Gain TFs.  Excitation Gain TFs must be divided from OUT2/EXC and OUT1/EXC measurements to get accurate OLGs:

OUT2/EXC = EXC_GAIN/(1 - OLG) = CLG

To get OLG data from the Exc Gain TF and CLG, run my script ctn_labdata/scripts/EXC_to_OUT2_OLGwriter.py:

python EXC_to_OUT2_OLGwriter.py EXC_GAIN_TF.txt CLGTFs*.txt

It will print out one OLG txt file for every CLG txt file you put in.  It writes the OLGs into another ctn_labdata/data/ directory... works great.

Finally, make a distrbution of your OLGs using ctn_labdata/scripts/TFdistributionPlotter.py:

python TFdistributionPlotter.py OLGTFs*.txt --title 'OLGs from OUT2/EXC with open loop correction' --yAxisLimitPercent 50 --yAxisLimitDegrees 50

This will make a PDF of two merged plots, attached below if you have imagemagick on your computer.  It will also automatically produce a tar with all the OLGTFs*.txt data files, the merged plot, and the script itself in it.


North UGF = 300 kHz

South UGF = 400 kHz

Phase margin is probably 180 degrees off...?

North Uncertainty ~ 5 % and 3 degrees

South Uncertainty ~ 10 % and 5 degrees

These seem like really solid measurements of the FSS loop gain.  I actually believe them for once.  Especially since there are 10 of them for each... we can take 1000 overnight if we feel the need.

I'm gonna try and take like 10 Crossover TFs for both paths, and see where we have "coherence" (read: low uncertainty).  Then maybe we can get PZT and EOM TFs we actually believe, or at least ones with uncertainty budgets.

Attachment 1: 20170831_195251_OLG_from_North_OUT2_over_EXC_29-08-2017_221042_Merged.pdf  590 kB  | Hide | Hide all
20170831_195251_OLG_from_North_OUT2_over_EXC_29-08-2017_221042_Merged.pdf 20170831_195251_OLG_from_North_OUT2_over_EXC_29-08-2017_221042_Merged.pdf
Attachment 2: 20170831_195401_OLG_from_South_OUT2_over_EXC_30-08-2017_002657_Merged.pdf  723 kB  | Hide | Hide all
20170831_195401_OLG_from_South_OUT2_over_EXC_30-08-2017_002657_Merged.pdf 20170831_195401_OLG_from_South_OUT2_over_EXC_30-08-2017_002657_Merged.pdf
Attachment 3: 20170831_200715_OLG_from_South_OUT2_over_EXC_30-08-2017_002657.tar.gz  510 kB
Attachment 4: 20170831_200850_OLG_from_North_OUT2_over_EXC_29-08-2017_221042.tar.gz  421 kB
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