PSN-L Email List Message
Subject: Re: New Lehman seismometer pivots
From: Dave Nelson dave.nelson@...............
Date: Sat, 02 May 2009 16:02:47 +1000
As I told you
several weeks ago and Bob McClure said within the last
couple of days .....
"DO SOMETHING ABOUT THE WIRE LEAD TO THE COIL!!! You cannot
leave it hanging loose from the boom. Cut it near the lower pivot,
secure it to the boom, and join it with coils of fine copper wire to
terminals on the frame. The terminals should be located as near to the
lower pivot as possible."
Jon.... You MUST do this you, will NEVER achieve long
period, free motion of the
arm until you get this sorted out. It is absolutely essential to
get rid of that huge
thick cable coming off the pivot end of the boom, it will be totally
attempt you make to try to get any decent sort of period from the
Until you change that, almost anything else you do to the unit will be
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
( 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
At 01:58 PM 5/1/2009 +0000, you wrote:
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.
After the weekend I am going to do one more change. I plan to change
setting of the arm. So it has not such sharp angle, but I belive that
hampering my effort in getting the frequancy below 0.4Hz, as sharp
means faster movement of the arm.
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