## 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
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 ??
regards
geoff

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

Hi

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.

Regards.
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)
> SQR = SQUARE ROOT OF()
> 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
> SINE or COSINE
> 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.
> http://www.jonfr.com/myndir/v/geology/lehman/p5240001.jpg.html
>
> I can send psn file to anyone how wants.
>
> Regards.

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