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Message ID: 13867     Entry time: Fri May 18 19:59:55 2018
Author: Jon Richardson 
Type: Configuration 
Category: Electronics 
Subject: AUX-PSL PLL Characterization Measurements 

Below is analysis of measurements I had taken of the AUX-PSL PLL using an SR560 as the servo controller (1 Hz single-pole low-pass, gain varied 100-500). The resulting transfer function is in good agreement with that found by Gautam and Koji (#13848). The optimal gain is found to be 200, which places the UGF at 15 kHz with a 45 deg phase margin.

For now I have reverted the PLL to use the SR560 instead of the LB1005. The issue with the LB1005 is that the TTL input for remote control only "freezes" the integrator, but does not actually reset it. This is fine if the lock is disabled in a controlled way (i.e., via the medm interface). However, if the lock is lost uncontrollably, the integrator is stuck in a garbage state that prevents re-locking. The only way to reset this integrator is to manually flip a switch on the controller box (no remote reset). Rana suggests we might be able to find a workaround using a remote-controlled relay before the controller.

Attachment 1: SR560_OL.pdf  168 kB  Uploaded Fri May 18 21:11:45 2018  | Hide | Hide all
SR560_OL.pdf
Attachment 2: SR560_CL.pdf  212 kB  Uploaded Fri May 18 21:12:07 2018  | Hide | Hide all
SR560_CL.pdf
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