PSN-L Email List Message

Subject: Re:Noise
From: rsparks rsparks@..........
Date: Sun, 13 Apr 2008 06:26:26 -0700

Hi Dick,

I took a look at your posting.  Nice job of collecting information and

For reference, I collected one hours noise from this morning.
My seismometer is a tilted vertical with a single long spring supporting
the sensing coil.  The spring is the hinge.  I post under the station
identifier "EBGZ".  The seismometer is in the basement.

 From looking at your pictures and FFT, I wondered if all of your
components are either securely assembled or placed on three point
mounts.  Four point mounts or components resting on flat surfaces can be
unexpected balanced between two semi-stable positions.  If so, the
microsiems or quakes can move the components between those two positions
resulting in high frequency noise.

Another source of noise can be the hinges.  The AS-1 actually has three
hinges if  you count the spring attachment points as moving
connections.  I don't know if lubrication with a light oil would help or
not.  The problem from hinges is that all hinges have some friction, and
the motion in a seismometer hinge starts and stops.  Static friction is
always greater than moving friction so there is a small "tremble" as the
transfer between static and moving occurs.   This "tremble" would be
recorded as noise.

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.

Certainly the wind can cause noise but you are probably well aware of
the magnitude of wind and other locally generated noise sources.

Good luck on your noise hunt.


> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 1                                                           |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Noise
> From:    "Thomas Dick" 
> Date:    Sat, 12 Apr 2008 21:45:03 -0500
> I have never been satisfied with my setup. I would like some suggestions =
> on where to look for the noise I still get on my units. Among the things =
> that I have enjoyed identifying included wind, walnuts falling on the =
> porch roof, a microwave oven, garbage trucks(empty and full), falling =
> trees, an assortment of caterpillars and shovels moving dirt and a =
> seismic truck testing soils in my area for liquifaction. If anybody has =
> the time, I put a rather large PDF file (~2.5 megs) on this site =
> My eventual goal is to get to the =
> level of the rest of the PSN event submissions. Your suggestions would =
> be welcomed.


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