PSN-L Email List Message
Subject: Re: Seismograph noise problem
From: Roger Sparks rsparks@..........
Date: Mon, 11 Feb 2008 06:35:25 -0800
Hi Larry,
The description of your seismometer seems very similar to mine, except
for the mount of the sensor cover.
I drilled three holes in the concrete floor, then put expansion bolts
in. The result is three 1/4 inch bolts extending about 2 inches above
the rug.
On top of these three bolts I laid a 3/4 inch thick particle board large
enough to support the seismometer cover. I stepped on the board both to
seat it and to ensure that the supporting bolts were solid. As I
recall, I re tightened the bolts after the first step-on, and
repeated the procedure.
I took the precaution of supporting the seismometer cover with three
support points, to prevent rocking of the cover. It sounds like you
accomplished the same thing with flexible/soft cover supports. My
seismometer goes inside of the cover.
I am very satisfied with the mounting now. You can see my occasional
postings from Ellensburg, Wash. on the PSN web site.
Good luck,
Roger
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> Subject: Re: Seismograph noise problem
> From: Larry Conklin
> Date: Sun, 10 Feb 2008 10:39:43 -0500
>
> Hi Roger,
>
> I it very interesting that you have had a similar problem, and I
> appreciate your suggestions. I my case, the sensor in in the basement,
> sitting on a concrete floor. Several years ago I epoxied three small
> aluminum plates to the floor for the settling screws to sit on. My
> concern at the time was that turning the leveling screw against the
> concrete was grinding into the floor, leaving concrete dust under the
> screw. One of the probable flaws in my construction is that the
> leveling screw is very small (#4) and more than likely not really firm
> enough. But, when I'm not being "haunted" the thing performs pretty
> well. Seems like problems stemming from the mechanical design shouldn't
> be episodic the way I have having them. I am using a 3 point mount, and
> the other two feet (base of the triangle) are sturdier.
>
> One thing that your comments encourage me to revisit is the way the
> cover over the sensor is made. It is made of 1/4/inch particle board
> and a little heavy on the heavy side. I is just sitting on the base
> frame of the sensor, held down by it's own weight. There are soft
> plastic feet attached where the contact is made to the frame. I don't
> normally make a point of pressing everything down to reseat things after
> i adjust it. Never occurred to me to do that. One thing I did try
> since this last episode started was to put a little piece of tape under
> each foot, to introduce a little "sqisshyness" to prevent the kind of
> "micro-rocking" that you apparently had. I didn't see any obvious
> difference.
>
> Guess I'm going to have to embark on a real science project.
>
> Larry
>
>
>
>
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