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Entry  Wed Oct 30 00:02:25 2013, Jenne, Update, LSC, LSC demod boards need some thought 
    Reply  Wed Oct 30 01:22:56 2013, Jenne, Update, LSC, REFL 165 demod phase adjusted 
       Reply  Wed Oct 30 01:44:13 2013, Jenne, Update, LSC, MICH and PRCL gains adjusted (Config file saved) 
          Reply  Wed Oct 30 03:36:51 2013, Jenne, Update, LSC, MICH and PRCL UGFs change with ALS enabled 
             Reply  Mon Nov 4 15:46:17 2013, Jenne, Update, LSC, Thoughts and Conclusions from last week's PRMI+2arms attempt 12x
                Reply  Tue Nov 5 19:39:27 2013, Jenne, Update, LSC, OpLev time series OpLevs_during_PRMI_2arms.pdf
    Reply  Wed Oct 30 03:33:17 2013, Rana, Update, LSC, LSC demod boards need some thought 0309.png
       Reply  Wed Oct 30 08:32:55 2013, Evan, HowTo, Computer Scripts / Programs, matplotlibrc 
Message ID: 9313     Entry time: Wed Oct 30 01:22:56 2013     In reply to: 9312     Reply to this: 9314
Author: Jenne 
Type: Update 
Category: LSC 
Subject: REFL 165 demod phase adjusted 

Quote:

For tonight, Rana has put a coax 100 MHz highpass filter on the input to the REFL165 demod board.

 This of course changes our demod phase.  Rana plotted a 4th order elliptic filter in Matlab, and from the plot determined that we should expect around 60 degrees of difference in our phase. 

To actually set the phase, I locked PRMI on AS55Q and REFL33I (MICH gain = -8.0, PRCL gain = +0.05, with 1's in the matrix elements).  I then turned on the PRCL oscillation notch (564 Hz), and turned on the sensing matrix's drive at that frequency, and looked at the spectrum of REFL165. 

The previous REFL165 demod phase was 96 degrees, so I was looking around either 36 degrees or 156 degrees.  The phase that minimized the peak in the Q signal while driving PRCL was 37.5 degrees.  Good work Matlab/Rana.

I then looked at the transfer functions between REFL33 and AS55 and REFL165, to see if there were any sign flips that happened.  There were not.  As expected, it was just a little extra phase delay.

I was able to lock PRMI with REFL 165 again after this phasing, and I am now taking transfer functions of the MICH and PRCL loops to make sure that we have the gains about right.

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