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Earth Signals
By: Dave Johnson

I have often wondered if any interesting electrical signals could be observed with copper probes driven into the ground.  As illustrated below. Three copper rods would be driven into the ground. The separation might be about 10 feet between rods.  The center rod is used as the reference for the other two. 

The three rods would be connected to an instrumentation Amplifier.  Instrumentation Amps provide very high common mode rejection.  Only signals which produce a differential voltage would be Amplified.  I would expect to see a lot of 60Hz or 50Hz signals picked up by the rods, caused by nearby power leakage.  To remove those signals, a notch filter could be added before additional signal Amplification.
What kind of signals could be picked up?  Iím not sure.  I do know that some voltages have been produced by quartz rocks, deep in the ground.  When subjected to pressure and small earth quakes, the piezoelectric nature of quartz can produce sizeable voltages.  Perhaps the act of walking between the electrodes would produce a detectable voltage. Could small insects and larger burrowing animals also produce voltages? 
I would love to see someone build such a circuit and give it a try.

Please send comments to me

July 2010     Issue 11

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