Resistivity machines...for real?

[cliffscot]

Interested to know more about TEM systems? Where should I look?

 

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[Tim Williams]

Who makes the TEM systems?

Tim

 

[99thpercentile]

One of the previous questions was about TEM systems. One of the more common system is the PROTEM from Geonics (www.geonics.com). It comes in three versions, the 47, 57 and 67 depending on how much power you need and depth of investigation. I think the price range is from about $80K to $150K.

For the question about inexpensive resistivity systems, read the link below. There was an amatuer archaeology group in the UK with the same desire. One of there members was an electronics engineer. He determined that he could make a four electrode system that was comparable to the Geoscan Research system that could sell for $1000. The problem came when you need to pass UL or CE certification to sell the units.

http://www.cix.co.uk/~archaeology/cia/resistivity/resist.htm

The post by geowizard was an excellent explanation of how instrument manufacture works. Resistivity systems work very well for near surface geophysics work, but only work in specific situations. Here are some of the companies that make resistivity systems.

IRIS Instruments
AGI
ABEM
Campus
Scintrex
Geoscan Research

 

[Landfar]

I Use resitivity meters in my work Resistivity meters are allot of work if you use them correctly I take as many as 900 readings in a day. But the Info you get back is very reliable . If your looking for treasure it helps if its large. I have looked at the resistivity meters in the medal detecting websites and I'm a bit skeptical mainly because of how simple the proceedure is to use them . If they really worked I would think noone would use the units I work with but they are the mainstay of the industry . So having said all that a simple low priced unit is the LANDMAPPER but unless your pretty sharp its going to take you awhile to learn how to take the readings and then you have to learn the software and I still do not have that understood but my son does . But its a real scientific device that will tell you whats in the ground down to 10 meters easy but if you think your just going to pop it out of the box and do it your nuts .. plus you better be pretty sure your in the area of a Target because just blind searching would be hopeless it take a very long time to do just one profile in a day. A profile is 10 meters deep 70 meters long

 

[geowizard]

Resistance and Resistivity are two different things;

We can measure resistance with an "ohm meter". Two probes, connect the probes and read the meter. There are only two probes.

The circuitry in the meter includes a battery. The battery provides a voltage that creates current flow through what ever it is you want to measure the resistance of. The meter is calibrated and the battery must be at the required voltage to get a correct reading. Always "zero" the ohm meter by connecting the leads together and adjusting the "zero" adjust or if it's a digital ohm meter, you press the "zero" button. Calibration can be checked with precision resistors.

Resistivity is a measurement of a volume of earth (or other material). Resistivity requires FOUR probes. Two probes generate a current that flows through the ground. Two other probes measure voltage at specified distances (spacing). A system to measure Resistivity can be made by the "average" person!

Here's how:

You need a voltage source and two steel stakes to connect the voltage source to the ground. The amount of voltage can be 24 volts to 36 volts for starters. Place the two stakes 10 meters apart. These are the "current" electrodes (probes). Use a switch to turn the voltage on and off. The measurement electrodes should be "non-polarizing". Metal measuring probes can produce a galvanic voltage that interferes with your readings. Do a search for non-polarizing electrodes. You will need a Digital Voltmeter to measure the current. The DVM connects in series with the battery and the probes. Be sure it is set to measure "current".

Place the two measurement electrodes at equal spacing between the two current electrodes (4 meters apart). Connect a DC volt meter between the two measurement electrodes. You can get a Digital voltmeter from Radio Shack. Doesn't need to be high priced!

When the switch is turned on, you will measure a voltage between the two measure electrodes. After each measurement, the battery polarity should be reversed. The reason is because the voltage leaves the ground slightly charged.

Next, I will tell you the rest of the story to calculate Resistivity and offer advice on distance to place probes, etc.

- Geowizard

 

[woof!]

http://www.treasurenet.com/forums/m...-anybody-used-gpl-200-accumeter-superpro.html

 

[Seden]

I just looked on ebay and there are two Associated Research Vibrogrounds for sale. They are 4 terminal units. There is the model 293 for $99 that comes with 4 earth probes and the model 263 (what I've got) for $150. There is free earth resistivity software on the internet.

Randy

 

[Bumbalawski]

Would the Associated Research Vibroground model 263 be decent enough for void or cave detection? I am not an avid treasure hunter and only have one treasure project on the plate. I am an avid caver and this unit may work for us, but I would like some input on its capabilities such as depth. Any opinions would be greatly appreciated.

Don Carns Jr.

 

[Treasure_Hunter]

Smart max, welcome to Treasurenet, I am sorry but you can not post links to websites selling detector supplies if they are not supporting vendor.

 

[HiiiQ]

Hi Aaarth iv'e been in another country and didn't visit this forum too often. for a person of you're abilityes one would expect that a bilionair would have better things to do....