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IDing metals with the GS5- Part 2- Out of the box.

bakergeol

New member
I had just received my upgraded GS5 and decided to bench test it with my new Coiltek Platypus DD elliptical coil to see if any of my settings needed to be changed. So I dragged out my nuggets (9 and 13 grams)and did the customary tests. First I did the GB mode at the 3:00 position. As expected the 9 gram nugget produced the expected high tone and the 13 gram nugget produced the expected low tone. Then I moved the GB to the 10:00 position and tested the 13 gram nugget. Here the nugget should ring in as a low tone(low tone here=non ferrous). Well it did produce a low tone in the middle of the coil but the toe response was a good high tone. I checked it with other intermediate sized low conductors(lead)with the same results. I could not repeat this test with other metals. Now I just know there is a piece of AL out there that will give a similar response like this however I just haven't found it yet. After testing countless trash AL from various sized AL cans, flat lids, different screw caps and large pull tabs I was starting to learn that even these had different responses( toe and center).

The question is how far can one go in IDing different metals with the GS5 or would one want to? Clearly not a high priority for users in the past. After all the GS5 is a gold machine "hot" on low conductors not high conductors. However more knowledge isn't necessarily bad as the above settings provides a means to test if you may have a large mans gold ring and not another piece of large AL.

Perhaps we can borrow a page from the Infinium playboy here using elliptical coils. I have begun a chart listing different middle and toe responses for different metals using several settings. These are just bench tests for the time being. My basic setting for ID is the extreme counterclockwise 7:00 position with PD of 10. For example silver dimes and quarters will produce a low tone in the middle of the coil and a high tone on the toe. There are other metals that produce similar responses such as intermediate sized brass and screw caps. However adjusting the PD to 25 and the middle/toe response reverts to Low/Low which is unique. Intermediate size brass would be Low/High whereas screw caps would be High/High. Copper and brass also have different responses.

Perhaps I am being a bit anal about all this after all there are a lot of perfectly good VLFs who could do this quicker and cheaper. I guess I am a bit fascinated with IDing metals with a PI.

HH
George
 
Hi George,

Your results are interesting, as I have not fully investigated the ID possibilities of the GS5. The primary object was to achieve a good ground balance system, and any useful metal ID would be a bonus.

Different responses will be obtained on the toe/heel of the coil, than that obtained in the centre. This very much depends on the nature and orientation of the target to the coil's magnetic field. Take a coin such as a dime or nickel, which is high conductivity. Or we could take a flat gold nugget. In the centre of the coil, or anywhere on the coil axis, the field is vertical, and if the coin or nugget is lying flat, the field is at right angles to the major surface. This excites the primary eddy current path in the target and gives the longest signal decay and amplitude. In the case of the dime or quarter and 13gm nugget, this will result in a low tone. Take the targets to the toe or heel of the coil and the magnetic field is now predominantly horizontal and parallel to the targets major surface, rather than vertical to it. Eddy currents are now generated in the targets cross section, instead of the horizontal plane, and these currents will have a much faster decay due to the very much lower inductive path in which they flow. This results in the change to a high tone. The one target that gives the same tone anywhere across the coil face, is a sphere. It doesn
 
"...a low tone in the middle of the coil and a high tone on the toe."

Hi George,

Do you have a technical explanation for this phenomenon? It would be nice if one could eliminate the need for changing the settings to ID a target positively...

P. Al
 
I was too quick on the trigger...you answered the question I asked George, above. I should have read your post before firing off my message...

Nuggets come with various time constants and it might not be prudent to bypass any targets that are non-ferrous.

I'm looking forward to your explanation of the ferrous response...

P. Al
 
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