Hi Larry,

My experience parallels yours with loose mounted components.  I once 
went through a rug to concrete below and failed to make good contact 
with one screw on the concrete.  I was effectively floating on the rug 
with one of the three seismometer legs!   Very noisy!

Based on this experience, I am careful to make all mechanical contacts 
solid connections in some way.  I even drilled holes into the concrete 
and mounted my seismometer solidly.  I thought there was a small 
improvement in the noise level after taking this somewhat extreme measure.

I also avoid pivot points in favor of bending joints to avoid noise.  
Friction is present in our seismometers if there is a moving joint and 
mechanical friction is always noise.

Maybe look more carefully at any mechanical connection that might be 
loose, maybe  not only in the leveling screws.  Look also at the 
mounting of the surrounding air/insulating box, making sure it is not 
rocking from the ever present 0.2 Hz peak noise or more likely, the 
thermal air currents in your room.

Good luck,

Roger
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| Message 3 | '------ ------ ------ ------ ------ ------ ------ ------ 
------ ------' Subject: Haunted system misbehaving again From: Larry 
Conklin  Date: Tue, 19 Jun 2012 14:54:30 -0400 I 
have an SG sensor that has intermittently had serious noise problems, 
literally for years. Mechanically, it is very similar to the design that 
is shown on Larry's PSN web site, and it uses Larry's electronics board, 
which I believe he is no longer selling. When the thing is running 
properly I've been quite happy with it. But occasionally, for reasons I 
have never been able to pin down, it exhibits extreme low frequency 
noise, to the point where it is basically useless. The current episode 
began with the system running very well, but it was in need of leveling, 
which I've typically need to do every couple of weeks or so. Before I 
adjusted the leveling screw, it was quiet. After messing with it it 
became extremely noisy. So, you'd believe that it was some sort of 
mechanical problem, right? And I've had several other episodes that 
began the same way. This time, when I brought it upstairs on the bench, 
I did in fact discover that the lock nut on the leveling screw was 
loose, and I "fixed" the problem by re-tightening it. Ran pretty well 
for a week or so thereafter, but not really as quiet as it should be. 
Then, it spontaneously got quite noisy again, interspersed with periods 
where it ran ok. I have a lot of other history with seemingly mutually 
exclusive symptoms/probable causes, but the bottom line is I don't have 
a clue what is really going on. I'm tempted to believe that there is 
something subtle wrong with the electronics board, but in past attempts 
to trouble shoot it, haven't been able to find anything. If there is 
anyone out there who has one of Larry's SG boards that they're willing 
to part with, I'd be interested in buying it. If for no other reason 
than to rule out the board as the source of the problem. For the 
curious, I have a little web page that I dump drum reports up to daily. 
The report for today (so far) shows a particularly noisy day, but does 
include the quake that happened in the Aleutians this afternoon. The 
page also shows drum reports from the day this round of the problem 
started. The day started just fine, until the big transient that 
resulted when I went down and adjusted the leveling, at which point all 
hell broke loose. You can also see the consequences of two subsequent 
leveling adjustments later in the day. After that data was recorded, I 
didn't mess with the thing for maybe a week, until I finally got around 
to taking a closer look at it, at which point I realized that the 
leveling screw was loose and re-tightened it. I'd be very interested in 
anyone's thoughts on this problem. The link to my web page follows: 
http://home.roadrunner.com/~lwconklin/ Larry Conklin Liverpool, NY .-
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