PSN-L Email List Message

Subject: RE: Changes to my Lehman sensor
From: "Gary Lindgren" gel@.................
Date: Wed, 8 Apr 2009 09:52:41 -0700

Hi Jon,
Have you tried raising the front end of the sensor to increase the =
Were you able to measure the time it takes the undamped arm swing =
to reduce by 1/2 after a gentle push.

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
Behalf Of J=F3n Fr=EDmann
Sent: Tuesday, April 07, 2009 5:57 PM
To: psn-l@..............
Subject: Re: Changes to my Lehman sensor


I will change the wire layout when I get the new arm. I was adviced to
keep the coil on the arm, not the base it self.

The natrual period of the sensor as it was setup was around 0.3Hz. But
it's range was only limited to that.

J=F3n Fr=EDmann.

On mi=F0, 2009-04-08 at 06:43 +1000, Dave Nelson wrote:
> Hi Jon,
>                 having iron in that area within the field of the =
magnet is

> not a good idea
> you would be much better off to use brass  if you didnt want to use
>     I also notice from your photo's that your pickup wire from the =
> a rather heavy looking wire will also affect the movement of the arm.  =

> usual
> practice, if  a person insists of putting the coil on the arm, is to=20
> terminate the
> heavier wire at the pivot end of the arm and to use VERY FINE  from =
> termination,  say 24-28 SWG enamelled wire wound in a loose coil say ~ =
>   of pencil/ pen diameter, then terminate that fine wire on the base =
> seismom.
> and then run heavier wire  again to the electronics.
> I can almost guarantee that the way you have taken your wire off the =
> will have
> a serious effect on the free movement of the arm!
> Dave N
> Sydney
> At 07:32 PM 4/7/2009 +0000, you wrote:
> >Hi
> >I belive that I found the last problem (according to the idea). The =
> >problem is the alunium rod that I have used as an arm. I belive that =
> >was too soft to work properly and because of that I didn't behave
> >correctly.
> >I am going to replace it with iron based arm and there is going to be =
> >steel based end on it. I hope that gives me the resault that I want.
> >Regards.
> >J=F3n Fr=EDmann.
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