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Entry  Mon Feb 6 17:06:11 2012, steve, Update, SUS, oplev transferfunction of PIT: ETMY & ETMX ETMX_PIT.pngETMY_PIT.png
    Reply  Tue Feb 7 16:30:46 2012, steve, Update, SUS, ALL oplev PIT transfer functions 7x
       Reply  Thu Feb 9 16:46:02 2012, steve, Update, SUS, ALL oplev YAW transfer functions 7x
          Reply  Thu Feb 23 10:53:54 2012, steve, Update, SUS, oplev PIT transfer functions oplPITtrans.pdf
             Reply  Mon Feb 27 14:35:22 2012, steve, Update, SUS, oplev YAW transfer functions oplYAWtransf.pdf
Message ID: 6309     Entry time: Thu Feb 23 10:53:54 2012     In reply to: 6263     Reply to this: 6323
Author: steve 
Type: Update 
Category: SUS 
Subject: oplev PIT transfer functions 

 Oplev transfer functions PIT UGF were optimized to be at 2-3 Hz with 60 degree minimum phase margin by adjuting oplev gains.

Additional Notes by KI:

  • The PRM oplev has a tailored 3.3 Hz resonant gain in order to calm down a wobble during the lock acquisitions.
  • Also in the PRM oplev a 35 Hz elliptic cut-off filter wasn't  activated at the time when Steve measured it.
  • In both ITMs, elliptic cut-off filters seem to have higher corner frequencies compered with the others.
    • I guess these settings are from the old days.
  • ETMs and ITMs have whitening filters while the rest of the suspensions don't.
    • Without the whitening filters, normally the signals above 30 Hz are covered by some electrical noises or perhaps He-Ne laser intensity noise (#5630).
      • This is why we usually use the 35 Hz elliptic filters to roll off the control noises.
    • Since the ETMs and ITMs have whitening filters they potentially can have slightly higher corner frequencies in the elliptic filters.
      • Of course the corner frequencies need to be re-designed in terms of the amount of noise injection to the longitudinal motion.

 

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