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Entry  Fri Dec 15 17:05:55 2017, gautam, Update, PEM, Trillium seismometer DC offset Trillium.png
    Reply  Fri Dec 15 18:23:03 2017, rana, Update, PEM, Trillium seismometer DC offset 
Message ID: 13482     Entry time: Fri Dec 15 17:05:55 2017     Reply to this: 13483  
Author: gautam 
Type: Update 
Category: PEM 
Subject: Trillium seismometer DC offset 

Yesterday, while we were bringing the CDS system back online, we noticed that the control room wall StripTool traces for the seismic BLRMS signals did not come back to the levels we are used to seeing even after restarting the PEM model. There are no red lights on the CDS overview screen indicative of DAQ problems. Trending the DQ-ed seismometer signals (these are the calibrated (?) seismometer signals, not the BLRMS) over the last 30 days, it looks like

  1. On ~1st December, the signals all went to 0 - this is consistent with signals in the other models, I think this is when the DAQ processes crashed.
  2. On ~8 December, all the signals picked up a DC offset of a few 100s (counts? or um/s? this number is after a cts2vel calibration filter). I couldn't find anything in the elog on 8 December that may be related to this problem.

I poked around at the electronics rack (1X5/1X6) which houses the 1U interface box for these signals - on its front panel, there is a switch that has selectable positions "UVW" and "XYZ". It is currently set to the latter. I am assuming the former refers to velocities in the xyz directions, and the latter is displacement in these directions. Is this the nominal state? I didn't spend too much time debugging the signal further for now.


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