PSN-L Email List Message

Subject: Re: Did I get 12 second period ?
From: "Geoffrey" gmvoeth@...........
Date: Mon, 25 May 2009 11:00:38 -0700

Hello Mr. Frimann;

I understand you live in cold country.
Could it be possible that ice will
somehow throw your entire
house out of level however slight
that may be ??
Freezing around the foundation ?
An error of only a fraction of a degree
from level will make a difference with the device
you are using. By comparison a geophone
will operate with more slop ( greater displacement
in orientation ). I think my geophone has a slop of
5 degrees from level. ( HS-10-1 ).
Possibly there is something magnetic on your boom
attracting to the magnets ??

----- Original Message ----- 
From: "Jón Frímann" 
Sent: Monday, May 25, 2009 5:54 AM
Subject: Re: Did I get 12 second period ?


The floor is level, this is the same floor where I keep my geophone,
with any issues.

However, the lehman sensor appears to be this high so I can get 12 to 20
second period. I am not sure why that is.

The only problem that I am dealing with now is that once I have setup
the correct period. I something find that the coil slides to the magnets
and gets stuck there. I do not know why that movment happens. I am
trying to fix that issue.

Jón Frímann.

On sun, 2009-05-24 at 22:48 -0700, Geoffrey wrote:
> It Seems To Me your floor was not level to begin with ?
> You most probably needed an angle of 1 degree or less
> from level ?
> I figure a little over 2 degrees for only 5 seconds
> using trig to figure the effect on the acceleration
> of gravity.
> P=2PiSQR(L/g)
> P = period in seconds
> Pi = 3.121(whatever)
> L = length of pendulum in inches
> g = gravity in inches per (second squared)
> g' = SINE or COSINE of the anglular displacement from zero g
> If you fix L
> at current gravity
> you change angle according to
> like g sin(angle) relative to horizontal
> or vertical.
> At vertical you got full g
> but at horizontal or inverted its zero.
> Sort of vectored by a lever arm.
> A spring with a linear constant acts
> just like a pendulum.
> If it takes 10 inches to get one second on a
> pendulum it also takes ten inches of extension
> of a spring to get one second.
> Or so it seems to me.
> In Physics class we used this frictionless
> puck floating on a rail at different angles
> to show how it could affect the acceleration.
> Frictionless on a cushion of air.
> ----- Original Message ----- 
> From: "Jón Frímann" 
> To: "PSN-Postlist" 
> Sent: Sunday, May 24, 2009 1:35 PM
> Subject: Did I get 12 second period ?
> Hi all
> I did one little change to my lehman seismometer. I did rase the front
> of the seismomter up from where it was. This appears to have incresed
> it's period to about 12 seconds.
> Here is are pictures of what I did.
> I can send psn file to anyone how wants.
> Regards.


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