PSN-L Email List Message

Subject: Re: New Lehman seismometer pivots
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Sat, 02 May 2009 10:40:51 +0000


The wire is not the issue. As it currently is it not loose. But I did
place it nicely in regards to the boom and it's movement. The boom it
self is free to move without issue.

I am going to fix a lot of minor issues after the weekend, then I am
going to post more pictures. I have posted new pictures here, they are
hopefully more detailed then before.

J=F3n Fr=EDmann.

On lau, 2009-05-02 at 16:02 +1000, Dave Nelson wrote:
> Jon,
>           As I told you several weeks ago and Bob McClure said within
> the last=20
> couple of days .....
> leave it hanging loose from the boom. Cut it near the lower pivot,=20
> secure it to the boom, and join it with coils of fine copper wire to=20
> terminals on the frame. The terminals should be located as near to
> the=20
> lower pivot as possible."
> Jon.... You MUST do this you, will NEVER achieve long period, free
> motion of the=20
> arm until you get this sorted out.  It is absolutely essential to get
> rid of that huge=20
> thick cable coming off the pivot end of the boom, it will be totally
> destroying any=20
> attempt you make to try to get any decent sort of period from the
> seismometer.
> Until you change that, almost anything else you do to the unit will be
> worthless.
> see how it is done on this commercial long period seismo that I and
> others are/have used .....
> you can see that in this case there are 2 pair of cables coming along
> the boom=20
> ( there are 2 pickup coils on this seismo)  they are terminated then
> VERY fine wire connects them to terminals on the vertical part of the
> frame.  Use 26 - 30 swg enamelled wire ( the finer the better).  and
> also use finer cable between the pickup coil and the terminal point
> that that thick cable you are currently using.
> cheers
> Dave Nelson
> Sydney
> Australia
> At 01:58 PM 5/1/2009 +0000, you wrote:
> > Hi
> > I am still unable to get the sensor frequancy below 0.4Hz. But this
> > design is a lot more flexable then the last one I used.
> >=20
> > After the weekend I am going to do one more change. I plan to change
> > the
> > setting of the arm. So it has not such sharp angle, but I belive
> > that is
> > hampering my effort in getting the frequancy below 0.4Hz, as sharp
> > angle
> > means faster movement of the arm.
> >=20
> > Regards.
> > J=F3n Fr=EDmann.


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