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Entry  Thu Dec 12 21:23:15 2013, ericq, Update, Green Locking, Better Xarm OLTF Dec12_Xarm_OLTF.pdf
    Reply  Thu Dec 12 22:12:17 2013, Koji, Update, Green Locking, Better Xarm OLTF 
       Reply  Fri Dec 13 11:47:11 2013, Gabriele, Update, Green Locking, Better Xarm OLTF 
Message ID: 9459     Entry time: Thu Dec 12 21:23:15 2013     Reply to this: 9461
Author: ericq 
Type: Update 
Category: Green Locking 
Subject: Better Xarm OLTF 

With the newly repaired PDH board, I spent some time with the x arm green PDH loop. I found it SO MUCH EASIER to measure the OLTF by injecting before the servo, instead of after it. (i.e. I added a swept sine from the SR785 to the mixer output (error signal) before the servo input). This is likely because the error signal is much flatter. I used a 10mV excitation across the whole frequency range (30-100kHz). 

Here's the OLTF. I'm working on fitting it and breaking it up into its constituent TFs, then making a rudimentary noise budget. 


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