I've been getting wobbly traces from my geophone since I put it outside in
the ground.  The period is about 40 secs, see http://macsmith.net/quakes .

The first geophone I put outside was "sealed" in a plastic length of pipe.
I didn't fill the pipe with anything.  The pipe actually has 2 geophones in
it, and they both generate wobbly lines.  I put another one out, this time
covered by a plastic box.  It was fine for a few days, but it too is now
wobbly - and is the one generating the current graphs.

I'm using a 4.5 Hz geophone from last year's group buy.  All the connections

are sealed with self amalgamating tape.  Obviously the effect is caused by
moisture, but I'm wondering where it is getting in.  The group buy geophones

seem to be sealed in rubber.

Any suggestions?



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