Measuring Telluric Currents – First Trial

Way back in November of last year (2010), I wrote a short little article on telluric currents, their history, and related applications.  Now, in case you’re unfamiliar with this topic (as I was prior to November of last year), here’s the executive summary: telluric, or earth currents, are electrical currents which travel through ground or water, primarily near the surface of the earth.  They may be naturally occurring (due to changes in the earth’s magnetic field via solar wind), or man-made (e.g, from mineral exploration).

Well towards the end of my previous post, I expressed a desire to try and measure these currents.  Unfortunately at that time, it was winter, and I was in the process of relocating to Iowa.  But now that I’ve settled in here, and the ground has finally thawed, I’ve gone out and performed a quick first measurement.  Here’s the procedure I followed:

  1. Obtain two 36″ lengths of standard rebar and 100′ of insulated 14 AWG copper wire (solid core works, but I used stranded for better contact with the rebar).
  2. Sand/file any rust from the surface of the rebar (to reduce contact resistance).
  3. Strip about two inches of insulation from the ends of the wire, then fray these ends and wrap them tightly around one end of each piece of rebar.  Cover these attachment areas with electrical tape.
  4. Cut the wire, which is now linking the two pieces of rebar, at any point (this is where the multimeter will be inserted).
  5. Space the two lengths of rebar as far apart horizontally as possible, then drive them into the ground as deeply as possible (in my case, this was about 20″).  For my first test, I configured the two so that they would point north to south based on the map shown here and my location in Iowa).  In other words, if I were to stand at the southern-most length of rebar, facing the other rod, I would be facing north.  They were separated by the 100′ of wire.
  6. Measure both current (short circuit) and voltage (open circuit).
  7. Finally, if anyone should question what the @#$% you’re doing pounding rebar into the ground, simple employ this catch-all excuse: “solar flare protection.

So, without further ado, I give you my results (in low-quality cellphone pic format):

Telluric Current - Well, it is measurable...

If you can’t quite make out that reading, my apologies.  The meter indicates 0.55mA (DC).  Yea, not too incredible, I know.  I also measured the voltage between the two rebar rods, but at just 105mV, it’s not terribly impressive either.  So, at best, we’ve got 14.5uW of power to play with – barely enough to run a digital watch (please see this excellent page on Thevenin equivalent circuits and the maximum power theorem for details on how that number was calculated).

Overall, these results are a little disappointing, both in quality and in quantity.  I had hoped to reconfigure my rods a couple of times so as to measure the current’s heading as well.  Unfortunately, for this test I picked a slightly wooded area that also happened to be teeming with mosquitoes.  I’ll do a lot of things for the sake of science, but serving as a meal for blood-sucking insects isn’t one of those things.

In the future, I’d like to leave the rebar in place for a while longer – say, 24 hours – and record data continuously during that time.  I’ve read in a number of sources that telluric currents tend to vary over the course of a day.  So, when I did my test this morning (8:30AM CST), I may have been measuring things as a low point.  The only trouble with capturing data for such an extended length of time is that I’ll need to find a more controllable location, and I’ll need to figure out how to log the data automatically.  I’ve got a few development boards I can probably re-purpose for that though…

So, in summary, for round two of testing I shall make the following changes:

  • Take measurements with the rods configured along different compass headings.
  • Log data for a consecutive period of at least 24 hours.

If anyone has other suggestions, please leave a comment.  Stay tuned for more.  Thanks!

9 thoughts on “Measuring Telluric Currents – First Trial”

  1. I tried something similar, but without the rods and the wire – in other words, i just stuck the voltmeter probes into the ground. They were not far apart. I got similar voltage readings to yours. Then I got a couple of screwdrivers and pushed those into the ground, and again measured the voltage – it was considerably higher, but still low.
    I was wondering if a voltage stepup circuit, like a joule thief, might be able to do something useful with this.

  2. Take the reading at dawn, the sun activates the field and it moves in fluctuations. Use an electrical conductive stone to magnify the readings. Best over water running in and out of the surface of the ground to get sunlight. Try getting the reading on a telluric or ley line conjunction.

  3. I did some tests in the mid 80’s.
    i used a 30 ft cross north south and east west, diodes on the end of the lengths of cable going into the ground, i used a scope across the n/s to e/w cables and recorded a slow 2 seconds per cycle waveform.
    Never did find out what it was.

  4. Hi i too have interest in potential from the Earth. Nathan Stubblefield was the main man in the 1800s, he made a self powering cell with special coils of wire which are interesting for your study. The battery location was important (Lay Lines) together with its orientation North South. I am experimenting at the moment after studying “The Works of Nikola Tesla” . Good luck with your project. DC

  5. Hello,
    if this post is still active, I will be interested. My first tests were close to my home and I got a classicla 50Hz signal evolving from about 100mV during the day upto ca. 800mV after dawn with no frequency change. Bars were 30′ apart. I am currently planing new tests with coax threads to filter out the 50 Hz. The bars will be 70′ apart. I heard that it is better to face the sun so the SE-NW axis seems OK especially for evening recording.
    I’ll come back when I will have recorded some signals

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