[GreenKeys] OT -- diy earthquake detector?

[Paul Heller]

Just look at that thing! I never saw anything like it. Thanks for sharing

Paul

> On Jul 8, 2019, at 8:17 PM, Gil Smith <gil at baudot.net> wrote:
> 
> Hey folks:
> 
> What with all the earthquake activity of late, I thought I would dig out an old geophone from decades ago (when I was with a company in Houston designing seismic gear for the oil industry).
> 
> A geophone is a moving-coil/magnet sensor for detecting velocity of the earth -- not the best sensor for rolling earthquake waves, as it is designed for detecting in just the vertical axis and is only moderately sensitive, but fun to try nevertheless.  
> 
> Since the geophone generates analog signals in the microvolt to millivolt range, it is just dandy to connect to a low-noise, low-freq adc system I happen to have lying around.
> 
> The geophone was placed on the concrete floor in my lab, and connected to channel 1 on the adc system.  No signal conditioning circuitry other than a damping resistor.  In the attached screenshot you can see significant pulses on the yellow channel 1 trace -- this is me walking on the concrete floor with no shoes on.  Perhaps there is a market in the security industry for protecting bank vaults :)
> 
> Probably won't see any distant earthquake activity from Cali, but I would bet it could detect local seismic events here in AZ (not that we have many).
> 
> You might say why not a modern mems accelerometer, which would be interesting to try also, but they are notoriously noisy, and it would be a digital interface with custom code -- the geophone connection took less than a minute of soldering to a connector.
> 
> But it got me looking around at diy seismometer sensors that are a better fit.  I might try building one for fun.
> 
> gil
> 
> 
> gil smith, AF7EZ
> greenkeys moderator
> gil at baudot.net <mailto:gil at baudot.net><geophone-and-adc.jpg><geophone-connected-to-squid.jpg><geophone-test-1.png>______________________________________________________________
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