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Old 11-16-2011, 12:20 PM
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Default A mystery...SOLVED...tell me why chains...

...are so hard to pick up and silver ones don't seem to come in where they should.

I just answered another post about this but I honestly don't have a logical answer.

I have come across a few funny things in my short travels through this md world of ours.

One that surprised me was if you throw down a quarter, or a bunch of quarters, I mean a whole lot of them they should come in as a high tone like they should.
Now if you take 50 of those quarters and put them in a roll and scan that, guess what...high tone quarter signal?
Nope, on my F2 I tried this with the signal was IRON!

Now Rudy explained this phenomena and it got another little discussion going on digging it all, which I usually do, and he suggested another experiment to do, as did Steve in AZ.

Evidently, all detectors can go nuts under the right set of circumstances.

http://metaldetectingforum.com/showthread.php?t=56924

Steve in Az suggested, and rightly so in my opinion, that these are very good reasons to learn to hunt by sound and not by just what is on our screens.
However, sometimes even these can try to fool you too.

My question for this particular thread is this...

Why can my Compadre, which is so sensitive it can pick up one tiny lone bead from the kind of chain that comes on nail clippers, can have so much trouble picking up a silver chain in the high end on my disc.

What I mean is on almost any object big or small that is silver the disc will max out...you can't disc these things out.
Now here is the weird part...
The chain you see below could only be picked up between foil and iron.
Even the clasp, which is much bigger than that little bead, will fade out at nickel and go no higher.
That's if the coil is almost touching it too, and this is because you lose depth as you add more disc. (Newbies, write that down).

If I take the clasp off the chain will my Compadre then act normally like it would with a silver dime or other silver object?

I have a theory that it might the chain part that is causing our detectors to act a little loopy because I have read plenty other posts from people that experienced the same thing.

I suspect part of the reason is that by design most detectors were made to sense round coin and ring like objects, not chain shapes.
As a matter of fact, I think chains confuse them.

Not sure if that's the answer, but all I know is silver chains, unless they are huge and thick, don't show up as silver.
Foil to nickel, yes...silver, no.

I have tested this with several chains and 3 detectors and it seems to hold true.
So riddle me this, Batman...why?
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Old 11-16-2011, 12:40 PM
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Probably the same phenominon that allows crumpled foil to show up as foil or be disc'd out, while a piece of tightly wadded foil can turn up a high signal.

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Old 11-16-2011, 01:07 PM
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Originally Posted by Longhair View post
Probably the same phenominon that allows crumpled foil to show up as foil or be disc'd out, while a piece of tightly wadded foil can turn up a high signal.
Okay, but I would still like to know why this stuff happens.

I guess I am after the ins and outs of the tech side of detectors, curious guy that I am.
How they work, or at least what is actually happening in that little brain of theirs inside the control box that causes them to react this way in these circumstances.

Not a big deal, I will still dig up mostly everything I come across, but when I get a question in my head I just get a little frustrated if I don't get an answer.

Maybe Rudy or some other techy engineer type will see this thread and have some input.

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Old 11-16-2011, 01:59 PM
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This past weekend, a friend and I were hunting tegether when he found a silver toe ring. I had him place it back in the ground and went over it with my E-Trac. Nothing. He went back over it again and got a very faint signal. Of course this was a re-burried item and the possible halo had been disturbed, but we were confused as well as it was not very deep but was giving us almost no signal.

Since then, I have been doing quite a bit of research on why this could be. Here are my findings...

When using a detector, and this varies greatly between what methods your detector uses, it creates a magnetic field that shoots into the ground. As you pass over a metal object, let's say a coin for now, it creates an electric current in that item. This current is called an Eddy Current. This current moves throughout the coin and creates its own magnetic field. This field is what the detector coil sees and interprets. It then takes all the input and either beeps a certain way, shows on a screen or both.

Now to the matter of different size, shape and wadding of items. These Eddy Currents flow differently depending on the items conductivity. Coins, nails, pull tabs, etc, have varied levels of conductivity and the detector usually reads them as what they are, but, if you change the shape of these items, say if a silver ring is not a "full" ring, or a is an unclasped silver necklace, or a peice of foil is wadded tightly, it will change the conductivity of that object. Not the conductivity of the metal mind you, just the way the current travels through the actual item.

To put it simply, lets say you have a full silver ring (a full O shape) and a silver ring that does not connect fully (basically a C shape), when the electric current passes through the full ring, it is able to travel in all directions easily, versus the incomplete ring, where it loses some current out of the broken ends.

Does this explain it better?

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Old 11-16-2011, 02:56 PM
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Originally Posted by DIGGER27 View post
Okay, but I would still like to know why this stuff happens.

I guess I am after the ins and outs of the tech side of detectors, curious guy that I am.
How they work, or at least what is actually happening in that little brain of theirs inside the control box that causes them to react this way in these circumstances.

Not a big deal, I will still dig up mostly everything I come across, but when I get a question in my head I just get a little frustrated if I don't get an answer.

Maybe Rudy or some other techy engineer type will see this thread and have some input.
It's the physics. The magnetic field generated by the Eddy currents induced by the transmit coil on the targets are very small in the case of a chain. Basically, because of the contact resistance between each link is relatively high, the Eddy currents are each confined to a single link in the chain. So, each small link in effect becomes a target. Because each link is small, it can't generate a large field for the receive coil to detect. Also, the links are pointing in somewhat different directions, so their individual magnetic fields don't readily add up to a larger field which would make for easier detection.

For the above reasons, chains are hard to detect. What usually "give them away" is an attached medal, or a sturdily built clasp.

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Old 11-16-2011, 03:09 PM
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And thaaaank you Rudy!

Knew you would come through for me!
You too, vexhold!

Now explain to me why every time I get into a line at Walmart or the bank, all the other lines seem to go faster.

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Old 11-16-2011, 03:56 PM
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Originally Posted by vexhold View post
Now to the matter of different size, shape and wadding of items. These Eddy Currents flow differently depending on the items conductivity. Coins, nails, pull tabs, etc, have varied levels of conductivity and the detector usually reads them as what they are, but, if you change the shape of these items, say if a silver ring is not a "full" ring, or a is an unclasped silver necklace, or a peice of foil is wadded tightly, it will change the conductivity of that object. Not the conductivity of the metal mind you, just the way the current travels through the actual item.

To put it simply, lets say you have a full silver ring (a full O shape) and a silver ring that does not connect fully (basically a C shape), when the electric current passes through the full ring, it is able to travel in all directions easily, versus the incomplete ring, where it loses some current out of the broken ends.

Does this explain it better?



Yes indeedy...explains it fine!

Now for those of you like me that like to watch the pretty moving pictures...this video nicely illustrates your point, I would say.

From 53Silver, who is a member here under a different name which I will not divulge to protect the innocent.


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Old 11-16-2011, 04:08 PM
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Saw a post on Youtube a few days ago. A guy and found a small, thin gold ring. It was broken, as stated above, when he passed it in front of the coil it had one tone. When he would press the ends together to complete the ring (circuit) it gave off a completely different signal. Now I know why.

thanks,
CC
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Old 11-16-2011, 06:49 PM
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Originally Posted by DIGGER27 View post
And thaaaank you Rudy!

Knew you would come through for me!
You too, vexhold!

Now explain to me why every time I get into a line at Walmart or the bank, all the other lines seem to go faster.
For the same reason that when you change lanes in traffic, the one you changed to slows down while the one you where in speeds up.

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Old 11-16-2011, 08:16 PM
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The Compadre also has an auto-retune. Check and see if the signal is in the middle of the coil or occurs afterwards, as an override.
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Old 11-16-2011, 09:09 PM
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Super thread & thanks for starting it, I learned so much.

Much like you I get frustrated when I can't rap my brain around a technical aspect.
Now it has been simply and clearly explained.

Another good reason to dig those odd "junk" signals.
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Old 03-11-2013, 11:50 AM
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Good question digger. This is why I tell the newbies to listen up when you speak.

I learned something I had absolutely no idea about. Good stuff vex and Rudy.

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Old 03-11-2013, 12:42 PM
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That is some good stuff--thanks!

I had something similar last week after I got my F2. I was practicing on my property (brand new to the hobby) and we have an old, old unpaved county road that's no longer in use that's close to my house. I was picking up lots of trash and iron signals so I notched out iron and was digging a pull tab here and there finally got a strong zinc signal (I think it was zinc) about 6" deep in the middle of the road. I had to get the big shovel from my house to dig through the compacted soil and finally dug up about a 3.5" ring about half an inch thick that was encapsulated in thick rust--in fact I'm pretty sure the whole thing is rust through and through. This puzzled me because the ring was obviously made out of iron and iron was descriminated out, yet the detector still hit on it as a different metal. I asked a very knowledgable local MD man about it who explained that things like that can happen due to the eddies of ring-shaped objects. I didn't really get it, but took his word for it.

The explanations posted above make it easier to undertand, though.

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Old 03-11-2013, 01:00 PM
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Thanks for the explanation, guys. My only problem with the Compadre is my eyes-for the life of me I can't see some of the tiny objects it sometimes detects. I have considered taking a magnifying glass but have since decided if it's not coin-size I'm not gonna worry about it. As for the Walmart question- I work there. That place is so screwed up-anything can happen. For just an example, after a BAD inventory, one of the managers was explaining how they found some items NOT in their proper place on the shelf (and why wasn't this found BEFORE inventory) and that's one of the reasons for the losses. HELLO! They STILL counted the items.
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Old 03-11-2013, 01:22 PM
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Originally Posted by sllingshot47 View post
Thanks for the explanation, guys. My only problem with the Compadre is my eyes-for the life of me I can't see some of the tiny objects it sometimes detects. I have considered taking a magnifying glass but have since decided if it's not coin-size I'm not gonna worry about it. As for the Walmart question- I work there. That place is so screwed up-anything can happen. For just an example, after a BAD inventory, one of the managers was explaining how they found some items NOT in their proper place on the shelf (and why wasn't this found BEFORE inventory) and that's one of the reasons for the losses. HELLO! They STILL counted the items.
This probably won't make or break your day sllingshot but I happen to like Walmart, I don't work there and never have but unlike most that shop there that just run in grab their stuff b*tch & complain if it isn't in stock and say most of the workers that work there don't know beans, I have alot of respect for the people that work there, never met anyone that wasn't willing to help & never found anyone that worked there that ever acted like they didn't want to work there whether they do or not. I'm glad that we have a Walmart not too far from me (about 12 miles) as we don't have much up here.
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Old 03-11-2013, 02:23 PM
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Originally Posted by DIGGER27 View post
Okay, but I would still like to know why this stuff happens.
These are machines that do a simple task. They send out a signal, then when it comes back, based on the design, they do what they are programmed to do. There are too many tangible variables, depth, soil content, object size and orientation, object's amount of metal content (10k, 14k etc). Then add in the ones you don't see, like radio signals, cell phone use, power lines, solar flares and any other electro-magnetic frequency that the machine is being hit with. So the machine gets the signal (possibly corrupted by interference) and based on it's program it tells you what it is most likely going to be based on the signal, and your custom settings.

I too believe most of the programming is based on the objects being coin sized and round.

All I can say is just enjoy the mysetery and keep hope alive that the next signal will be something of value.

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Old 03-11-2013, 04:08 PM
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Originally Posted by joefish72 View post
All I can say is just enjoy the mysetery and keep hope alive that the next signal will be something of value.
Nothing is a mystery when you decide to dig it up and see.
I am very curious and it is the only way I know for sure to ease my mind.
No "what ifs" for me when I do this and as a bonus, I have a lot more chains and other great treasures in my collection.

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Old 03-11-2013, 04:20 PM
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Wait til you crack a gold with diamond ring on the way up like i did and the detector no longer sees it after it gets a crack in it. You'll really wonder how much gold rings and chains are out there we will never find with a detector.
By the way.Some gold chains are found by that little stainless spring in the clasp.None of the gold is setting it off. So some guys who say it was a sparky sound don't realize that is what stainless sounds like. It's not the clasp. Its the spring inside the clasp. I took one of the springs out and it eliminated finding the chain at all.

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Old 03-11-2013, 04:57 PM
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Originally Posted by Swing360 View post
Good question digger. This is why I tell the newbies to listen up wjhen you speak.

IS learned something I had absolutely no idea about. Good stuff vex and Rudy.
Just trying to help out any way I can.
I posted the pic with the silver chains on another forum and several members seemed impressed.
Lots of hunters do not know this information, several never seem to find many chains, even silver ones, and we all know they are out there.
The fact is, if you don't dig trash and odd signals you will cut your chances of finding one way down.

Like anything else, the more you know and understand how things work, the better you can deal with things and ultimately be more successful.

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Old 03-11-2013, 05:12 PM
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A fine silver chain I scooped up came in a solid 41, just above iron and no clasp on the chain.

Name:  89968578croprs.jpg
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Another big fat 1/2 oz silver chain came in a 65 or just above pull tab.

I have yet to find a Gold chain, I will this year! All chains are hard to find, I run the MD wide open and listen for the odd sounding hit.

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