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Entry  Wed Nov 11 12:50:10 2009, Jenne, Update, PEM, Seismometer Noise Characteristics HuddleTest_Aug2009data.png
    Reply  Thu Apr 22 20:28:40 2010, Jenne, Update, PEM, Seismometer Noise Characteristics Gur1_Gur2_noise.png
       Reply  Thu May 27 23:59:54 2010, rana, Update, PEM, New Foam Box installed Untitled.png
          Reply  Fri May 28 00:40:53 2010, rana, Update, PEM, DAQ down 
             Reply  Fri May 28 10:44:47 2010, josephb, Update, PEM, DAQ down 
                Reply  Tue Jun 8 18:39:36 2010, rana, Update, PEM, DAQ down 
                   Reply  Tue Jun 8 20:52:25 2010, josephb, Update, PEM, DAQ up (for the moment) 
          Reply  Fri May 28 11:26:35 2010, Jenne, Update, PEM, New Foam Box installed 
          Reply  Tue Jun 1 11:47:14 2010, steve, Update, PEM, lead balls on concrete P1060269.JPG
             Reply  Wed Jun 9 19:47:08 2010, nancy, Update, PEM, lead balls on concrete 
                Reply  Thu Jun 10 07:53:14 2010, Alberto, Update, PEM, LaTeXlabs 
                   Reply  Thu Jun 10 10:58:02 2010, Koji, Update, General, LaTeXlabs 
                      Reply  Thu Jun 10 11:10:21 2010, Alberto, Update, General, LaTeXlabs 
Message ID: 2833     Entry time: Thu Apr 22 20:28:40 2010     In reply to: 2237     Reply to this: 3002
Author: Jenne 
Type: Update 
Category: PEM 
Subject: Seismometer Noise Characteristics 

Quote from elog 2237, 11 Nov 2009:

The attached plot shows the spectra of the 3 Z axes of the 3 seismometers we have (this data is from ~20Aug2009, when the Ranger was in the Z orientation) in Magenta, Cyan and Green, and the noise of each of the sensors in Red, Blue and Black.  The noise curves were extracted from the spectra using the Huddle Test / 3 Corner Hat method.  The Blue and Black traces which are just a few points are estimates of the noise from other spectra.  The Blue points come from the Guralp Spec Sheet, and the Black comes from the noise test that Rana and I did the other day with the Ranger (elog 2223).  

I'm not really happy with the black spectra - it looks way too high.  I'm still investigating to see if this is a problem with my calibration/method....

 So, as it turns out (surprise), I'm a spaz and forgot a 2*pi when calibrating the Guralp noise spectra from the spec sheet.  I noticed this when redoing the Huddle Test, and comparing my Spec Sheet Guralp noise with Rana's, which he shows in elog 2689.  When going from m/s^2, the units in the spec sheet, I just tilted the line by a factor of frequency.  Koji pointed out that I needed a factor of 2*pi*f.  That moves the Guralp spec line in the plot in elog 2237 (to which this entry is a reply) down by ~6, so that my measured noise is not, in fact, below the spec.  This makes things much more right with the world.

In other news, I redid the Huddle analysis of the 2 Guralp seismometers, ala Rana's elog 2689. The difference is now we are on the granite slab, with soft rubber feet between the floor and the granite.  We have not yet cut holes in the linoleum (which we'll do so that we're sitting directly on the 40m's slab).

Rana> this seems horrible. Its like there's a monster in there at 6-7 Hz! Either the seismos are not centered or the rubber balls are bad or Steve is dancing on the granite slab again.

 

Attachment 1: Gur1_Gur2_noise.png  131 kB  | Show | Show all
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