Urgent Earth Resistivity Question to Carl

[junkie]

In the write-up of this equipment the probe configuration is for horizontal profiling.

Can I use this same equipment for vertical profiling?

How deep can this equipment, with its output voltage of 10volts, penetrate? Specifically, can I have a good reading at 20 to 30 meters deep?

How would I know if I can't go deeper?

Thanks.

[Carl]

Re: Urgent Earth Resistivity Question to Carl

I know very little about ERM capability. I do know that the depth achieved depends on probe spacing, up to a point, but I don't know where the diminishing limit is. Probably strongly dependent on the soil. So, with multiple passes at different probe spacings, you can probably get a rough vertical profile. Steve Ryland can probably help, over on the TreasureNet Geophysics forum.

- Carl

[junkie]

Re: Urgent Earth Resistivity Question to Carl

thanks

[Untitled]

EPE earth resistivity meter

To measure resistivity more than a few cm down you will need a system that supplies a much higher voltage. To get profiling of perhaps 15m depth you are looking at at least 200v. The EPE system is really designed for surface anomalies arising from differences in soil type (perhaps ditch fill) it was never intended for geophysical prospecting.
There are several depth sounding resistivity systems on the market but you will have to pay several thousand pounds for them.
It IS possible to design and build your own, using commercial data acquisition components and software, after you have master edthe power supply! After this comes the data processing and inversion. Technically complex in it's own right. And beware...the pseudo-section method (apparent resistivity plotted at 45 degress to the electrode separation) does NOT give you the depth of the reading. Proper iterative inversion methods are required.

[Seden]

Steve Ryland

Carl,
Steve Ryland died suddenly Feb.2004. He and his wife ran Cal-Gold in Pasadena. I only talked with him on the phone once and talked to his wife shortly after his passing and offered my condolences.

Junkie-I would forget about the EPE Resistivity meter and concentrate on getting a real resistivity meter. I just looked on ebay and there's a 3 point measurement Vibroground for a buy it price of $25!!! These units are made by Assoiciated Research and are high quality. I bought the model 3439 which can be used as a 4,3 or 2 point measurement meter. They have the old vibrator that operates at 97hz and takes the battery voltage up to 125 vac and I paid $70 for it on ebay.

Far as software goes easiest to input values for us lay persons would be VES 1.30 by G.R.J. Cooper(free software). The other free program is called 2D Resistivity and IP Forward Modeling by M.H. Loke. Whoa learn to master this and you've got very good graphics on what's beneath you.

Far as study material-from the many Geophysics books I own (the classics) the best straight forward explanation is in a book called "Looking into the Earth" by Alan E. Mussett and M.Aftab Khan published by Cambridge. This awesome book covers all the geophysics survey methods with beautifull color illustrations and it's like it was written for us hobbiests-no joke.

So I'm waiting for it to rain here in Southern California so I can use mine. The soil is bone dry.

Hope this helps.

Randy

[Seden]

Forget the 3 terminal meter!

I posted the above after 1am and after I shut my pc off I realized the 3 terminal in incompatible with Schlumberger and weiner arrays and so couldn't be entered into the VES software. To be honest,I've never seen a 1D,2D or 3D Resistivity done with anything but a 4 terminal unit.

But do and try and get ahold of a professional 4 terminal AC bridge and save yourself alot of grief and disapointment.

Randy

[Carl-NC]

Carl,
Steve Ryland died suddenly Feb.2004. He and his wife ran Cal-Gold in Pasadena. I only talked with him on the phone once and talked to his wife shortly after his passing and offered my condolences.

Yup, I heard about his passing. This thread (and my reply) date back to 2003. I met Steve at the Mesa Gold Show around 2000. Nice guy, and very knowledgable about geophysics.

- Carl

[Agraz]

the instrument in e bay.



Uploaded with ImageShack.us

this image in e bay

[Agraz]

I build this similar



Uploaded with ImageShack.us

8- electrode
8- spool cooper cable
1- central electrode
1- sensitive galvanometer ( I use galv. 50's) whit central ampere meter.
1- inverter
1- hammer



Uploaded with ImageShack.us


Uploaded with ImageShack.us

[Agraz]

Uploaded with ImageShack.us



Uploaded with ImageShack.us



Uploaded with ImageShack.us



Uploaded with ImageShack.us



Uploaded with ImageShack.us



Uploaded with ImageShack.us