SE and Gold Rings

Ed in KC

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In a post yesterday, Carol used the expression “e-gads,” which is something I hadn’t heard for years, but it brought back memories of my mother, who used to use that term on occasion, usually an occasion brought on by me or my brother—she never cussed! Anyway, to make a long story short, I ended up getting into a box with various things that my mom left me, including some gold rings. One ring, a large 22k open wedding band that belonged to my paternal grandmother, when scanned over my SE coil, wouldn’t register at all, unless it was right by the coil. The same was true for a 10k open wedding band, but it wouldn’t register even if next to the coil, but when I scanned a closed 14k wedding band, it would register loud and clear. I changed coils, putting on my little X-5, thinking maybe it would pick the rings up, but I got the same results. Next I got my Bounty Hunter Land Star, exact same results with it; would neither of these detectors pick up a 22k or 10k ring—I was troubled, to say the least!
I turned the gain up to ten (it had been on 7), and now I was able to pick up the 22k ring at an inch-and-a-half, but that was it, and it was a faint, iffy signal at that. I looked over the 22k ring, wondering if it was counterfeit, then I got the idea to hold it closed together and pass it over the coil, and that made all the difference in the world; I could now pick it up at 7” over the X-5 coil with a loud, robust signal up to about 6”, and dying out ‘til 7”.
From now on, when I hunt tot lots, I’m turning the gain up to 10, and the sensitivity up as high as possible.
Second pic is of a diamond ring I found when I was a little kid: I found it lying in the street, and gave it to my mom. My parents took it to a jeweler, who said it was real, so then my mom gave it to her mom, because my grandmother had never had a diamond ring before, and it just happened to fit her. My mom got it back after my grandmother died, and then I got it back after my mother died.
HH'
Ed
 

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Minelabs have that problem even the Excalibur they when they do signal at least it was in my case it was a broken signal.. I don't know why but I have heard that around on the boards before.. I remember eyeballing a ring and running my Excal over it and not a peep from it :(
 
Minelabs have that problem even the Excalibur they when they do signal at least it was in my case it was a broken signal.. I don't know why but I have heard that around on the boards before.. I remember eyeballing a ring and running my Excal over it and not a peep from it :(

It was the same with my Bounty Hunter too; if the rings were open, neither detector would pick them up.:?:
 
It is the rare detector that is capable of detecting a smallish open gold ring. This is for the same reason that small gold chains or fragments are difficult as well.

This is because the Eddy currents induced on the ring are too small when the ring is broken.
 
what do you mean by open and closed? are these rings broken?
where do they show on the smart screen?
and what setting do you hunt in most of the time
sorry for all the questions, but I am trying to learn all I can about the SE
I had read in another forum about a guy who had been asked to look for lost gold ear ring with an SE When he scanned the other ear ring,, it was a good sized hoop but it wouldn't register he figured it must be fake or hollow
Thanks
Cliff
 
what do you mean by open and closed? are these rings broken?
where do they show on the smart screen?
and what setting do you hunt in most of the time
sorry for all the questions, but I am trying to learn all I can about the SE
I had read in another forum about a guy who had been asked to look for lost gold ear ring with an SE When he scanned the other ear ring,, it was a good sized hoop but it wouldn't register he figured it must be fake or hollow
Thanks
Cliff

The 22k and the 10k are cut in two at the bottom.
The smart screen is just a graphical representation of the digital numbers: 0-31 on the conductive vertical axis, and 0-31 on the ferrous horizontal axis.
I change my settings to try to be as efficient as possible for the ground conditions I'm hunting; in a normal, not overly trashy park setting, I adjust the sensitivity to a digit or two below falsing, in manual mode; variability-10, limits-10, response normal, sounds-conduct, threshold so it's just audible, discrimination-i use a pattern of discing out at sixteen, with a little notch at the bottom over to probably eighteen or nieteen and up probably 4. Deep mode, but if it's trashy I run it in fast, which I think really helps seperate targets. I play with my set-up quite a bit in different situations, and I'm still very much in the learning proccess.
 
It is the rare detector that is capable of detecting a smallish open gold ring. This is for the same reason that small gold chains or fragments are difficult as well.

This is because the Eddy currents induced on the ring are too small when the ring is broken.

That makes sense, and I can see it on a small chain link, but it seems like a ring would be big enough to show up, but obviously not.
Thanks!
 
That makes sense, and I can see it on a small chain link, but it seems like a ring would be big enough to show up, but obviously not.
Thanks!


Quite a few of my rings I find with my PI are open (broken) but I'm not advising you to use a PI ;) the less that use a PI the better for me and my friends :D
 
Quite a few of my rings I find with my PI are open (broken) but I'm not advising you to use a PI ;) the less that use a PI the better for me and my friends :D

PIs are just for beach hunting aren't they; if I used one in my area, I think I'd just have to start sifting all the iron out with a screen!:lol:
 
PIs are just for beach hunting aren't they; if I used one in my area, I think I'd just have to start sifting all the iron out with a screen!:lol:

The new TDI PI from Whites is not for the beach but relic hunting..
 
what do you mean by open and closed? are these rings broken?
where do they show on the smart screen?
and what setting do you hunt in most of the time
sorry for all the questions, but I am trying to learn all I can about the SE
I had read in another forum about a guy who had been asked to look for lost gold ear ring with an SE When he scanned the other ear ring,, it was a good sized hoop but it wouldn't register he figured it must be fake or hollow
Thanks
Cliff

The SE is arguably one of the best detectors out there for ferreting out the deep silver on a turf area, but they are not so good on the low conductors which gold is. A broken ring (open) is even worse.
 
Broken rings, and gold chains indeed, are less conductive than plain gold rings.

Did the test after buying my quattro one month ago, with similar disappointing results.

This is the reason why I never sold my C Scope Minidisc (CS 550). That little one-knob TR detector runs 100 Khz (the gold frequency !! :D) and, with its small 6" concentric coil, it is a thin gold killer.

Thin white gold rings with precious stones are equally less conductive and also difficult to find.

HH

Nick
 
Rudy hit it on the head. The drawing I made below (don't laugh) shows what happens with eddy currents in a whole ring versus a broken ring. The red lines represent the eddy currents generated in the rings.

In a whole ring, large eddy currents are able to flow around the perimeter of the ring. In a broken ring, the path for the eddy currents is limited, so only small eddy currents can flow. This causes the broken ring to not be detected as easily as the whole ring.

You can simulate this with a small loop of copper wire too. Cut a piece of copper wire long enough to form a 1" diameter loop (approximately 3" length). With the ends of the copper wire touching, making a closed circuit for the eddy currents to flow, the copper wire will be detected at a large distance. If you disconnect the ends of the copper wire, breaking the path of the large eddy currents, the loop will not be detected very far at all.

Another experiment is to turn the closed loop of copper wire (or a fine gold band) 90 degrees to the coil. This will not be detected at the same distance as when the loop is parallel to the coil, again due to the eddy currents not forming around the large circumference of the loop.

One more experiment is to take a copper penny and measure the maximum distance at which you can detect it. Now, take the penny and drill a large hole through the center of it, removing 1/2 to 3/4 of the material, to form a ring. Measure the distance at which you can detect the copper ring. It should be at a greater distance than when the penny was whole, because you have now created a large, well defined path around the outside of the penny for the eddy currents to flow. Prior to drilling, the eddy currents are not well-defined and tend to flow in smaller loops throughout the entire area of the penny.

Fun science stuff, huh?
 

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Interesting Hobbes, I studied the effects of eddy currents in iron cores in electronic school, but from what I remember, eddy currents were always small circular currents. I've just now been playing around with a piece of copper wire, and it seems to me that there may be more to it than eddy currents: it may actually be more like lines of flux in an inductor, because if I make several coils in the same direction, with the ends tied together, I get a very powerful signal, but if I make several coils with half being wound in the opposite direction, so any induced current would be opposite polarities on each side of the coil, I get a lousy signal. I think this could actually be a complicated issue, with eddy currents being part of it, but actual induced current also playing a part?
 
Interesting Hobbes, I studied the effects of eddy currents in iron cores in electronic school, but from what I remember, eddy currents were always small circular currents. I've just now been playing around with a piece of copper wire, and it seems to me that there may be more to it than eddy currents: it may actually be more like lines of flux in an inductor, because if I make several coils in the same direction, with the ends tied together, I get a very powerful signal, but if I make several coils with half being wound in the opposite direction, so any induced current would be opposite polarities on each side of the coil, I get a lousy signal. I think this could actually be a complicated issue, with eddy currents being part of it, but actual induced current also playing a part?

Ed, you are correct that it is a complicated issue, one of which I am not an expert in, but I know just enough to be dangerous. :lol:

You may recall from school that the study of eddy currents was probably based around iron cores in a transformer. A solid iron core will conduct large eddy currents, causing a great loss of efficiency in a transformer. That is why iron cores are typically gapped and laminated, to reduce the eddy current flow, similar to the ring versus broken ring example.

You can think of a simple induction-balanced metal detector, with a transmit and receive coil, as an air-core transformer where the primary and secondary windings are decoupled. When you bring a target near the coils, current is induced in the target, which is then induced into (detected by) the receive coil.

Bringing a loop of wire into proximity of the coils is similar to adding an additional short-circuited winding to the transformer. Lots of current will flow in the loop (eddy currents) and the receive coil will pick that up easily.

In your opposing coils example, the induced current is indeed in opposite polarity, causing zero current to flow in the circuit (Kirchhoff's current law).
 
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