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Entry  Sun Sep 4 18:43:55 2016, awade, DailyProgress, DAQ, Setting up PID slow controls for FSS, issues with fb2 on restart 100_0203.JPG
    Reply  Mon Sep 5 18:37:16 2016, awade, DailyProgress, DAQ, Setting up PID slow controls for FSS, issues with fb2 on restart 
       Reply  Wed Sep 7 13:03:56 2016, awade, DailyProgress, DAQ, Setting up PID slow controls for FSS (South path) SLOW_PID.plScreen_Shot_2016-09-07_at_12.46.47_PM.pngScreen_Shot_2016-09-07_at_12.52.44_PM.pngScreen_Shot_2016-09-07_at_12.58.05_PM.png
          Reply  Fri Sep 23 17:21:02 2016, awade, DailyProgress, DAQ, Setting up PID slow controls for FSS 100_0210.JPG
             Reply  Mon Oct 3 18:10:26 2016, rana, DailyProgress, TempCtrl, Setting up PID slow controls for FSS 
                Reply  Tue Oct 4 11:08:27 2016, awade, DailyProgress, TempCtrl, Setting up PID slow controls for FSS 
Message ID: 1722     Entry time: Fri Sep 23 17:21:02 2016     In reply to: 1718     Reply to this: 1731
Author: awade 
Type: DailyProgress 
Category: DAQ 
Subject: Setting up PID slow controls for FSS 

I realized that there is no low pass filtering of the acromag output to the north path slow controls input. I was just going to copy the LP filter used for the south path, but am not sure what it is doing to cut off HF.  I measured its TF with a SR780 and its not LP filtering at all (loaded with 50Ω or not).

This is the filter (pictured below), its just a shunt capacitor (22µF) installed in parallel across the BNC terminals. 

Present LP filter on south path

 

This should be fine I guess for cutting out ripple voltage. Am I missing something or do we want a more typical LP filter like an RC circuit to operate with a (say) 10 Hz cut off.  I'm not sure of the design motivations.

Quote:

A perl script is now implemented (running on acromag1) that gives PID control of the south laser temperature 'slow input'. (North cavity will be setup next).

The script (attached) was pulled from the fb2 machine controls home folder and was a version earlier attributed to Tobin Fricke 2007-01-09 then modified variously by Frank, Tara and now me. I have removed various proprietary channel calls buried in the script and moved them to the preamble variable declarations section of the script so they are easily modifiable in the future. The following software channels were declared in the IOCTEST_BIO_generic.db database file (on acromag1) so that the perl script's PID constants can be accessed and changed from front end interface:

  • C3:PSL-ACAV_SLOWFSS_SETPOINT (Setpoint monotor voltage the PID aims for)
  • C3:PSL-ACAV_FSS_SLOWPID_KP
  • C3:PSL-ACAV_FSS_SLOWPID_KI
  • C3:PSL-ACAV_FSS_SLOWPID_KD
  • C3:PSL-FSS_SLOWPID_TIMEOUT  (i.e. the time step interval of the do loop)
  • C3:PSL-ACAV_FSS_SLOWPID_BLINK (Status blinker to show script is ticking over)
  • C3:PSL-ACAV_FSS_SLOWPID_EN (Loop engaged 1 = yes, 0 = no)

These channels were then added to the C3PSL_LASER_SLOW.adl panel as sliders and buttons for user control. 

Screen shot of current front panel

The loop was engaged but needs some tuning.  I will search back through the elog and see if there are any nominal starting values and then optimize. There is a note from from Tara in this post PSL:1155 that he put a low pass filter on both the output AND the input.  There are little glitches in the data (as you can see below). It might be prudent to put this kind of filtering on the input, or at least adjust the averaging. 

First PID lock engage for South Slow laser controls, some oscillations that need damping
ADC has some glitches, not sure how this will affect the control loop or
if will be inherently filtered by the pole of the crystal temperature repsonse

 

 

Quote:

Computer fb2 rebooted eventually (>1 hour).  fb2 now has a much faster response to ssh logins which would take ~20 s to ask for a password before.   

 

 

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