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Entry  Mon Oct 14 17:01:43 2019, anchal, Notes, Laser, South Laser Switched Off! SouthLaserStopped.pdf
    Reply  Mon Oct 14 18:30:14 2019, anchal, Notes, PMC, South PMC Error Signal Oscillations SPMCMixerOutOscillations.pdf
       Reply  Tue Oct 15 18:54:16 2019, anchal, Notes, PMC, South PMC further problems 
          Reply  Wed Oct 16 16:56:43 2019, anchal, Notes, PMC, South PMC won't work with it's own Servo Card only 
             Reply  Wed Oct 16 17:33:08 2019, Koji, Notes, PMC, South PMC won't work with it's own Servo Card only 
                Reply  Wed Oct 16 18:46:58 2019, anchal, Notes, PMC, South PMC started working somehow :( 
                   Reply  Wed Oct 23 17:39:44 2019, anchal, Notes, PMC, South PMC started working somehow :( 
                      Reply  Fri Oct 25 16:50:12 2019, anchal, Notes, PMC, South PMC problem debugging efforts 
                         Reply  Tue Oct 29 19:10:59 2019, anchal, Notes, PMC, South PMC problem debugging efforts SPMC_Diagnostics.pdf
                            Reply  Wed Oct 30 15:15:28 2019, anchal, Notes, PMC, Replacing U5A AD602 didn't solve the issue. 
                               Reply  Wed Oct 30 18:35:31 2019, anchal, Notes, PMC, Issue closed 
                                  Reply  Mon Nov 4 12:15:01 2019, anchal, Notes, PMC, Changing the autolocking method 
Message ID: 2469     Entry time: Wed Oct 30 18:35:31 2019     In reply to: 2468     Reply to this: 2471
Author: anchal 
Type: Notes 
Category: PMC 
Subject: Issue closed 

It turns out I did not have a full understanding of the problem and it was not really a problem. The blanking (pin 4) on U5A AD602 doesn't shut down the channel, it just reduced the gain by 100. So if the gain in previous stage is large enough, the lock can still be acquired. And that's what was happening.

Ideally, we need to keep the AD602 on all the time and lock by scanning the offset with low gain. The loop will catch the lock (the exact same thing I thought was a problem) and once that has happened, we can just increase the loop gain the set value.


Presently, the gain behind the U5A AD602 is 101, which is kind of high. I just need to check if the above-mentioned locking method would work robustly without wrongly getting locked to any higher-order modes with the gain slider set to some threshold value within -10 dB to 30 dB. If that can't be done, I might have to reduce the gain in the first stage. For now, the cavities are locked and beatnote is traveling towards set point.

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