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Entry  Tue Oct 8 08:08:18 2019, gautam, Update, PEM, PEM BLRMS anomaly PEManomaly.png
    Reply  Wed Oct 23 11:49:21 2019, gautam, Update, PEM, PEM BLRMS anomaly seisAll_20191021.pdfspecGrams.zip
       Reply  Thu Oct 24 18:37:15 2019, gautam, Update, PEM, T240 checkout 
          Reply  Tue Nov 5 12:37:50 2019, gautam, Update, PEM, T240 interface unit pulled out T240_recenter.pdfffPotential.pdf
             Reply  Wed Nov 13 19:34:45 2019, gautam, Update, PEM, Follow-up on seismometer discussion seisAll_20191111.pdfffPotential.pdf
                Reply  Wed Nov 13 20:15:56 2019, rana, Update, PEM, Follow-up on seismometer discussion 
                   Reply  Wed Nov 13 23:40:15 2019, gautam, Update, PEM, Follow-up on seismometer discussion seisAll_20191111_1Hz.pdf
                      Reply  Thu Nov 14 12:11:04 2019, rana, Update, PEM, Follow-up on seismometer discussion 
                      Reply  Fri Nov 15 00:18:41 2019, rana, Update, PEM, Follow-up on seismometer discussion MCshake.pdf
                         Reply  Fri Nov 15 12:16:48 2019, gautam, Update, PEM, Follow-up on seismometer discussion BS_ZspecGram.pdf.zip
                            Reply  Mon Nov 18 14:32:53 2019, gautam, Update, PEM, Follow-up on seismometer discussion 
                               Reply  Tue Nov 19 21:53:57 2019, gautam, Update, PEM, Follow-up on seismometer discussion seisxSpec.pdf
Message ID: 15013     Entry time: Tue Nov 5 12:37:50 2019     In reply to: 14992     Reply to this: 15022
Author: gautam 
Type: Update 
Category: PEM 
Subject: T240 interface unit pulled out 

I removed the Trillium T240 DAQ interface unit from 1X4 for investigation.

It was returned to the electronics rack and all the connections were re-made. Some details:

  1. The board is indeed a D1000749-v2 as Koji said it is. There is just an additional board (labelled D1001872 but for which there is no schematic on the DCC) inside the 1U box that breaks out the D37 connector of the v2 into 3 D15 connectors. I took photos.
  2. Armed with the new cable Chub got, and following the manual, I ran the re-centering routine.
    • Now all the mass-monitoring position voltages are <0.3 V DC, as the manual tells me they should be.
    • I noticed that when the seismometer is just plugged in and powered, it takes a few minutes for the mass monitoring voltages to acquire their steady state values.
    • The V indicator reported ~-2V DC, and the W indicator reported -3.9V DC.
    • While running the re-centering routine, I monitored the mass-position indicator voltages (via the backplane D15 connector) on an oscilloscope. See Attachment #1 for the time series. The data was rather noisy, I don't know why this is, so I plot the raw data in light colors and a filtered version in darker colors. Also, there seems to be a gain of x2 in the voltages on the backplane relative to what the T240 manual tells me I should expect, and the values reported when I query the unit via the serial port.
    • We should ideally just install another Acromag ADC in the c1susaux box and acquire these and other available diagnostic information, since the signals are available.
    • We should also probably check the mass position indicator values in a few days to see if they've drifted off again.
    • Looking at the raw time series / spectra of the BS channels, I see no obvious signatures of any change. 
    • I will run a test by locking the PRC and looking for coherence between the seismometer data and angular motion witnessed by the POP QPD, as this was what signalled my investigation in the first place.

Update 445pm: Seems to have done something good - the old feedforward filters reduce the YAW RMS motion by a factor of a few. Pitch performance is not so good, maybe the filter needs re-training, but I see coherence, see Attachment #2 for the frequency domain WF.

Attachment 1: T240_recenter.pdf  132 kB  Uploaded Tue Nov 5 16:03:16 2019  | Hide | Hide all
T240_recenter.pdf
Attachment 2: ffPotential.pdf  80 kB  Uploaded Tue Nov 5 21:07:01 2019  | Hide | Hide all
ffPotential.pdf
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