PSN-L Email List Message

Subject: Re: VBB-BB Tiltmeter info
From: "meredith lamb" mlamb1@.........
Date: Sun, 06 May 2001 09:38:40 -0700

sean@........... wrote:

> The abstract explains the principle of its operation. Since the VBB-BBT
> is insensitive to horizontal acceleration, which a horizontal seis
> senses, its output will only be the tilt noise of the pier environment,
> which a horizontal seis is also sensitive to, especially at long periods.
> So with identical tilt sensitivities, the signal from the VBB-BBT can
> be subtracted from that of the broadband horizontal seis, leaving only
> the true seismic signal of interest. The VBB-BBT signal must be digitized
> and processed identically to the broadband seismic signal.

I maybe presumptive on this, but it sounds like a seismic station
would likely need two of the VBB-BB's, one for each direction
orientation of a "companion" normal BB horizontal seismometer?
This leads up to the question of whether your tiltmeter is indeed
direction sensitive which I presume it is?  This sounds like a
very good "noise filter" which would give a much clearer seismic
picture with alot of better implications for professional 
installations and researchers.  No wonder Dr. Hutt with USGS
wanted you to pursue it with vigor!

> Regards,
> Sean-Thomas
> I will review the info on the bought magnet and the coil construction
> and post it tomorrow. I also have a box flexure design for the BBT that
> I also used to make a compact (10" long) horizontal broadband seis as a
> companion to a compact version of the the leaf spring vertical.

That should be very interesting also; its always nice to read of
leading edge material that inspires advancements; as you are
the only real instrumentation authority (teacher)that PSN benefits

Thanks, Meredith Lamb


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Larry Cochrane <cochrane@..............>