PSN-L Email List Message
Subject: Re: Which is which?
From: Kevin Brunt k.brunt@.........
Date: Fri, 11 Sep 2009 15:19:51 +0100 (GMT Daylight Time)
On Fri, 11 Sep 2009 10:00:30 -0400 Brett Nordgren
> Hi All,
> A few days ago, Dave Nelson in California was able to obtain the loan of a
> Nanometrics Trillium Compact-120, a professional quality triaxial packed
> into a can only slightly larger than a large geophone. Our plan is to
> compare its output with the home-built Force Balance Vertical running
> beside it.
> Soon after it was installed, California obliged with a nice 3.9 up the
> coast which gave us a modest sized test signal containing some higher
> frequency energy, which we could use to compare the two instruments. Both
> instruments' outputs were filtered with a 20Hz 4-pole low pass and the
> Trillium had a two pole high-pass added at 1/50Hz, in order to match the
> 50-second low frequency rolloff of the FBV, since its own rolloff was at
> 120 seconds.
> The results are shown at http://bnordgren.org/seismo/TvsFBV01.gif or the
> somewhat larger http://bnordgren.org/seismo/TvsFBV01.jpg
> Question: Which is the $7000 Trillium and which is the FBV built by Dave?
> Brett .
You have checked that you haven't connected both channels to the same sensor? :)
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