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40m Log |
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Wed Apr 26 01:00:23 2017, gautam, Update, General, DRMI locking  
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Fri Apr 28 02:04:36 2017, gautam, Update, General, DRMI locking
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Fri Apr 28 13:56:26 2017, rana, Update, General, DRMI locking
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Mon May 1 16:29:51 2017, gautam, Update, General, DRMI locking 
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Mon May 1 21:45:54 2017, ericq, Update, General, DRMI locking
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Wed May 3 18:45:45 2017, rana, Update, General, DRMI locking
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Thu May 4 19:03:15 2017, gautam, Update, General, DRMI locking - preliminary MICH NB   
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Fri May 5 10:13:02 2017, ericq, Update, General, MICH NB questions
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Fri May 5 12:10:53 2017, gautam, Update, General, MICH NB questions
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Sat May 6 21:52:11 2017, rana, Update, General, MICH NB questions
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Wed May 10 01:56:06 2017, gautam, Update, General, MICH NB - OL coupling  
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Wed May 10 16:53:38 2017, rana, Update, General, MICH NB - OL coupling
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Wed May 10 17:17:05 2017, gautam, Update, General, DAC / Coil Driver noise
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Wed May 10 17:46:44 2017, gautam, Update, General, DAC / Coil Driver noise - SRM coil driver + dewhite board removed
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Thu May 11 09:45:46 2017, rana, Update, General, DAC / Coil Driver noise - SRM coil driver + dewhite board removed
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Thu May 11 18:59:22 2017, gautam, Update, General, SRM coil driver + dewhite board initial survey 
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Fri May 12 01:36:04 2017, gautam, Update, General, SRM coil driver + dewhite board LISO modeling 
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Fri May 12 12:34:55 2017, gautam, Update, General, ITM and BS coil driver + dewhite board pulled out
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Fri May 12 18:50:08 2017, gautam, Update, General, ITM and BS coil driver + dewhite board pulled out
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Mon May 22 13:37:01 2017, gautam, Update, General, DAC noise estimate 
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Tue May 23 22:58:23 2017, gautam, Update, General, De-Whitening board noises
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Thu May 25 19:27:29 2017, gautam, Update, General, Coil driver board noises
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Mon May 29 16:47:38 2017, gautam, Update, General, Coil driver boards reinstalled  
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Tue May 30 16:02:59 2017, gautam, Update, General, Coil driver boards reinstalled
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Thu Jun 1 00:10:15 2017, gautam, Update, General, Coil driver boards reinstalled
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Fri Apr 28 19:32:06 2017, gautam, Update, General, DRMI locking - PRCL angular FF 
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Message ID: 12983
Entry time: Wed May 10 17:17:05 2017
In reply to: 12979
Reply to this: 12984
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Author: |
gautam |
Type: |
Update |
Category: |
General |
Subject: |
DAC / Coil Driver noise |
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Suspension Actuator noise:
There are 3 main sources of electronics noise which come in through the coil driver:
- Voltage noise of the coil driver.
- The input referred noise is ~5 nV/rHz, so not a big issue.
- The Johnson noise of the output resistor which is in series with the coil is sqrt(4*k*T*R) ~ 3 nV/rHz. We probably want to increase this resistor from 200 to 1000 Ohms once Gautam convinces us that we don't need that range for lock acquisition.
- Voltage noise of the dewhitening board.
- In order to reduce DAC noise, we have a "dewhitening" filter which provides some low passing. There is an "antiDW" filter in the digital part which is the inverse of this, so that when they are both turned on, the result is that the main signal path has a flat transfer function, but the DAC noise gets attenuated.
- In particular, ours have 2 second order filters (each with 2 poles at 15 Hz and 2 zeros at 100 Hz).
- We also have a passive pole:zero network at the output which has z=130, 530 Hz and p = 14, 3185 Hz.
- The dewhitening board has an overall gain of 3 at DC to account for our old DACs having a range of +/-5 V and our coil drivers having +/- 15 V power supplies. We should get rid of this gain of 3.
- The dewhitening board (and probably the coil driver) use thick film resistors and so their noise is much worse than expected at low frequencies.
- DAC voltage noise.
- The General Standards 16-bit DACs have a noise of ~5 uV/rHz.
- the satellite box is passive and not a significant source of noise; its just a flaky construction and so its problematic.
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