PSN-L Email List Message
Subject: Re: Re:Noise
From: "Thomas Dick" dickthomas01@.............
Date: Sun, 13 Apr 2008 12:30:44 -0500
From looking at your pictures and FFT, I wondered if all of your
components are either securely assembled or placed on three point
Four point mounts or components resting on flat surfaces can be
unexpected balanced between two semi-stable positions.
I did use four pivot points on the Lehmans...a mistake I won't make again
.... the bases for the Lehmans are 1/4" steel these could be used as boat
anchors ... unfortunately I sold the boat! The support of the mental plates
that hold the magnets isn't as stable ... this could be an issue. But the
peaks at 4 hz is gound on the geophone buried outside!
If so, the microsiems or quakes can move the components between those two
resulting in high frequency noise
.. The AS-1 uses a knief edge rather than a hinge. The AS-1 sits in an old
refrigerator with the door closed. The pivot point on the booms of the
Lehmans is a stainless steel ball bearing. The only issue I haven't
addressed is that the Lehmans sit on concrete blocks sitting on the concrete
floor. From what you infer, this might be an issue. I raised the Lehmans up
off the floor so that I didn't have to bend over as much.
I collected one hours noise from this morning.
Mine are one minute but it would help know where you two are....???
Georgia??? Macon ...right?
You could test the electronic noise by locking the seismometer. I would
not expect much noise from electronics compared to the noise that will
come from the seismometer output.
suggestion under advisement
This issue has been around for some time. I even sent one amp board back to
Larry for him to look at. I put an isolation transformer and battery back up
to help smooth out the AC. I even had the local electric company come
out(firends in the right places) with special equipment and test the
incoming AC...nothing serious there.
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