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40m Log |
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Tue Dec 26 17:24:24 2017, Steve, Update, General, power outage
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Thu Dec 28 17:22:02 2017, gautam, Update, General, power outage - CDS recovery
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Thu Jan 4 14:39:50 2018, gautam, Update, General, power outage - timing error
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Fri Jan 5 21:54:28 2018, rana, Update, General, power outage - timing error
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Fri Jan 5 22:19:53 2018, gautam, Update, General, power outage - timing error
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Sat Jan 6 18:27:37 2018, gautam, Update, General, power outage - IFO recovery 
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Mon Apr 16 22:09:53 2018, Kevin, Update, General, power outage - BLRM recovery 
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Tue Apr 17 09:57:09 2018, Steve, Update, General, seismometer interfaces 
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Wed Apr 18 20:33:19 2018, Kevin, Update, General, seismometer interfaces  
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Fri Apr 20 23:36:28 2018, Kevin, Update, PEM, Seismometer BLRMs  
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Tue Apr 24 21:19:08 2018, Kevin, Update, PEM, Seismometer BLRMs   
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Wed Apr 25 17:44:39 2018, Arnold, Update, PEM, PEM Anti-Alias wiring
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Thu Apr 26 09:35:49 2018, Kevin, Update, PEM, PEM Anti-Alias wiring 
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Thu Apr 26 20:22:21 2018, Kevin, Update, PEM, ADC common mode rejection with new seismometer connections 
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Wed May 16 21:02:22 2018, Kevin, Update, PEM, ADC common mode rejection with new seismometer connections
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Thu Jun 14 15:24:32 2018, Steve, Update, PEM, ADC DAC In Line Test Boards are in
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Tue Jan 2 15:43:35 2018, Steve, Update, VAC, pumpdown after power outage
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Wed Feb 7 15:50:42 2018, Steve, Update, VAC, IFO pressure monitoring
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Message ID: 13849
Entry time: Wed May 16 21:02:22 2018
In reply to: 13794
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Author: |
Kevin |
Type: |
Update |
Category: |
PEM |
Subject: |
ADC common mode rejection with new seismometer connections |
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As described in this elog, the ADC for the seismometers now has the signals wired directly to the ADC instead of going through an AA board or other circuit to remove any common mode noise. This elog describes one test of the common mode rejection of this setup. Guantanamo suggested comparing directly with a recent spectrum taken a few months before the new setup described in this elog.
Today I took a spectrum (attachment 1) of C1:PEM-MIC_2 (Ch17) and C1:PEM-MIC_3 (Ch18) with input to the ADC terminated with 50 Ohms. These are two of the channels plotted in the previous spectrum, though I don't know how that plot was normalized. It's clear that there are now strong 60 Hz harmonic peaks that were not there before, so this new setup does have worse common mode rejection. |
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