## PSN-L Email List Message

Subject: Re: Incresing the period of a lehmans seismomter ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Sat, 09 May 2009 23:28:18 +0000

```Hi all

Thanks for the help of the weeks. I could not have fixed the issues with
out you all.

I am still having minor issues adjusting the period of my lehman sensor.
I am not sure if I have to move the boom up or down to increase the
period of my sensor.

Regards.
J=F3n Fr=EDmann.

On f=F6s, 2009-05-08 at 05:41 +0000, JAMES RIDOUT wrote:
> Jon,
>       I found it very confusing when setting the period for my
> seismograph, and for a=20
> long time took the period to be the time it takes the arm to swing
> from one side to the
> other.( I could never get much more than 10 seconds)!!.
>  But apparently I am wrong, The period is the time it takes for the
> arm to swing
> past the same point in the same direction twice. So if you hold the
> arm towards you
>  and let it go, as it passes the centre, start a stopwatch, then
> let the arm go to the other side,
> then back towards you , and as it passes the centre again press stop.
> This is the period.
>   Anyone please correct me if I am wrong. !!.
>                                                                 James
>=20
> --- On Fri, 8/5/09, J=F3n Fr=EDmann  wrote:
>=20
>         From: J=F3n Fr=EDmann
>         Subject: Re: Incresing the period of a lehmans seismomter ?
>         To: psn-l@..............
>         Date: Friday, 8 May, 2009, 2:08 AM
>        =20
>         Hi all
>        =20
>         I got the period down to 6 seconds at the lower end, but at 4 sec=
onds
>         the high end. But I have to do it adjust the period really slowly=
.. I am
>         not sure what I can detect at 6 seconds.
>        =20
>         Geoffrey, I know what you mean. I am trying to understand somethi=
ng in a
>         diffrent language and am trying to understand something that I ha=
ve not
>         got a big traning on.
>        =20
>         Regards.
>         J=F3n Fr=EDmann.
>        =20
>         On fim, 2009-05-07 at 17:04 -0700, Geoffrey wrote:
>         > Gee, I believe this to be one of those
>         > garden gate seismometers.
>         > I always thought of it as a modified
>         > pendulum changing the acceleration of gravity
>         > in a trigonometric fashion.
>         > This means the mass is the lowest point on the lever arm
>         > or you can not have stability.
>         > It manipulates the pull of gravity
>         > like Sine or Cosine of the angle relative
>         > to horizontal.
>         > I believe you guys are thinking much more
>         > complex then myself.
>         > You more than likely will never
>         > take souls like me very serious.
>         > Sort of like Rodney Dangerfield ???
>         >=20
>         > ----- Original Message -----=20
>         > From: "J=F3n Fr=EDmann"
>         > To: "PSN-Postlist"
>         > Sent: Wednesday, May 06, 2009 7:54 PM
>         > Subject: Incresing the period of a lehmans seismomter ?
>         >=20
>         >=20
>         > Hi all
>         >=20
>         > Tomorrow I am going to make the final changes to my lehman seis=
momter. I
>         > hope that this changes make the seismomter get down to 20 secon=
ds period
>         > at most.
>         >=20
>         > The only thing that I need to know is this. What is the best wa=
y to
>         > increase the period of my lehman seismomter ? Moving the boom d=
own or
>         > up ? Or do I have to do something else.
>         >=20
>         > Regards.
>        =20
>         __________________________________________________________
>        =20
>         Public Seismic Network Mailing List (PSN-L)
>        =20
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