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 Mon Jul 27 16:47:53 2015, ericq, Update, IOO, MC2 -> MCL Actuator TF 
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 Thu Jul 30 02:06:20 2015, Ignacio, Update, IOO, MC2 <-> MCL Actuator TF fitted
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Wed Aug 12 22:33:36 2015, Ignacio, Update, IOO, Re-measured MC2 -> MCL TF
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Fri Aug 28 20:15:49 2015, rana, Update, IOO, MC2 -> MCL Actuator TF
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Mon Aug 31 07:49:11 2015, ericq, Update, IOO, MC2 -> MCL Actuator TF
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Mon Aug 31 14:15:23 2015, Ignacio, Update, IOO, Measured the MC_F whitening poles/zeroes
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Message ID: 11539
Entry time: Fri Aug 28 20:15:49 2015
In reply to: 11447
Reply to this: 11548
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| Author: |
rana |
| Type: |
Update |
| Category: |
IOO |
| Subject: |
MC2 -> MCL Actuator TF |
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| qQuote: |
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I made a measurement of the MC2 actuator transfer function by injecting noise from 1-100Hz into LSC_MC2_EXC for about 15 minutes, then estimating the TF from MC2_OUT to IOO_MC_L with CSD/PSD. The inverse of this TF will be applied to their Wiener target data to give us the direct subtration filter we want.
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I think what happened here is you forgot to undo the MC_F whitening filter which is the Generic Pentek Interface board next to the MC servo board. I suggest you guys measure this on Monday so you can correctly estimate the MC length noise. And then perhaps undo the whitening in the anti-whitening filter of this filter bank so that the signal which is recorded is in units of kHz.
This should allow your online subtraction filter to be more correct: roughly speaking, the phase shift below a pole or zero is going to be 45*(f/fp) deg. Since we expect there to be 2 zeros at 15 Hz, it would be 9 deg phase shift at 1.5 Hz and limit the subtraction to ~80%. |