Friday, September 14, 2012

Home seismometer for ENA

Every 5 years or so, I review the state of the home seismometer.  These are really accelerometers and measure acceleration directly.  The latest technology uses a small proof mass where the motion is detected by capacitance.  The expensive seismometers use a micro-machined mass, and integrate to velocity.  The cheaper ones use a chip-scale mass, and output acceleration.

If you are in California and getting an earthquake every day, then you can use a 12 bit 2g chip, and still get a recording once in a while to make sure it works, and perhaps provide some calibration.  In the East, you can install these things for a "Big One', and never know if it actually works.  That's the big problem, you can slap down an accelerometer anywhere, and not know if you are on some horrendous local amplifier.  That's why when you see accelerations from an eastern earthquake, they are all over the map.

I worked with 16 bit 2g accelerometer chips, and that's still not good enough.  Regional earthquakes, are just a little fuzz with these things.  So I am waiting for cheap 24 bit 2g chips.  Haven't seen them yet, but can't wait to record earth tides!

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