PSN-L Email List Message
Subject: Re: Shaking house
From: Bob Hancock icarus@.........
Date: Mon, 16 Feb 2009 17:44:07 -0700
I have a seismometer located over 250 feet from my house. However
there are some things you might want to consider:
1. How often will you be accessing the instrument - this will
determine the type of vault and seismic pier that you set up (think
depth and accessibility). For example does you instrument require
periodic tweaking, if so, how often will you need to have direct
access to the instrument?
2. What are your temperature extremes. Do you live in an
excessively wet or dry climate, snow or hot sun? If you have an
external seismic vault, is it weather protected, and how hard is it to
access the instrument?
2. Regardless of where you place the instrument, temperature
stabilization is extremely important. If you have the instrument
temperature stabilized, you most likely have it covered, and this begs
the question, how easy will it be to access the instrument for tweaking?
3. Does your electronics require a differential receiver at the
point where your signal enters your house? This is in addition to and
prior to the A/D board. You might want to check if you need something
4. If you use a crawl space under a house, you will most likely
pick up tilting ground movement as the house is buffeted by wind, and
when people move around the house. However, this is dependent upon
the depth of the foundation, firmness of the ground, and external
forces that affect the house.
5. When I had my instrument located 75 feet from the house, I could
pick up the washing machine. I was able to filter it out when it
coincided with a seismic event, but that is something to think about.
6. The previous comment about the cable is very important. Ultra-
violet radiation can cut the life of an above ground cable. You
definitely want it buried, and placed inside something like PVC piping.
7. If you use some variation of a wireless transmission between the
instrument and your receiver, you need to think about the weather and
wind again. Do you have blowing dust and dirt where you live. If you
have periods of heavy rain, blowing dust or snow, it is likely that
you could loose your signal at least during these occurrences. You do
not want that to happen during a seismic event. You could get around
that with some type of temporary data storage at the instrument site,
and if the transmission cannot take place, it could be stored
temporarily at the instrument, but like everything else this adds
complexity and cost.
No simple answers - lots to think about. There are many more factors
to consider, but this will get you started in thinking about some of
the benefits and problems associated with an external installation.
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