Questions about "wrap-around"

Hi all!

I have some questions regarding "wrap-around;" I've heard the term used and know that it has to do with iron "wrapping around," from an ID perspective, into the range where high conductors should fall, but otherwise know very little else. I want to understand this better, so I had sent NASA-Tom a PM to see if he knew where I could find any info on the topic. He sent me a reply with some explanation -- which I'm posting below for the help of anyone else interested:

Quote

In electronics........ 360-degrees is commonly used........ especially when referring to O-Scope analyzation. When electromagnetically analyzing iron........ for ID purposes....... one of the components will go beyond 360-degrees........ back around/into the non-ferrous spectrum........ usually into the silver/copper conductivity spectrum. Although there are different inductive and reactive components to iron........ this 'wrap-around' beyond 360-degrees is quite problematic ....... as far as detecting/proper ID is concerned.

((( In a nutshell !!! )))

This explanation makes sense -- particularly with machines whose ID is a single-number readout, ranging from, say, 00-99 (i.e. a non-Minelab FBS unit).

However, I'm trying to figure out exactly how this applies to a Minelab Explorer. On the Explorer (which, like other FBS units uses a two-number ID system -- a "ferrous" number and a "conductive" number), things seem more complex in terms of applying the wrap-around concept.

For those who don't know, Ferrous and Conductive numbers on the Explorer both range from 00 to 31. UNLIKE the E-Trac and CTX, the FE number is NOT "normalized" to 12, which means each different target may have a different ferrous number, ranging from 00 to 31. For instance, here are some common air-test ID numbers of U.S. coins on the Explorer:

nickel 10-06
Indian Head penny 07-24
zinc penny 07-25
copper penny 04-28
dime 03-28
silver dime 03-29
quarter 00-29
silver quarter 01-29
silver half 00-28

Nails usually read in the high 20s to around 30 on both the FE and CO numbers, i.e. 27-29 might be a common nail ID.

Now, applying this to the wrap-around idea, there are some iron targets (some screws, small bolts, etc, as well as some hot rocks, etc.) that will read 00-31, in other words, the lowest FE number and the highest CO number. In this case, I am guessing that the reason for the 00 FE number is that it has "wrapped around" from what should have been a number in the roughly 25 to 31 range, and instead registered as "00." These 00-31 IDing targets, and the empty, airy sound of the tone, are easy to ignore. I am guessing this is a classic case of how "wrap-around" presents itself on the Explorer?

Now, here's an issue that I think is NOT a case of "wrap around," but not sure. This is the case where you get a coin-type ID off of the tip of a straight nail, when you hit it from a certain angle. I don't think that is a case of "wrap around," correct? That's more a case of the machine mis-identifying a target, as I understand it?

Finally, it's pretty well understood by Explorer users, I think, that on a deep coin, it's common for the FE number of a good coin to "degrade," i.e. to read much higher than "air test ID;" sometimes, the CO number will drop a digit or so, as well. For instance, it is not at all uncommon for a deep silver dime, instead of the standard 03-29 air-test ID, to read into the teens on the FE side, and fluctuate between 28 and 29 on the conductive side. I've dug many, many silver dimes with numbers bouncing around like 11-29, 13-29, 09-28, etc. Similar things happen with other deep coins. The CO number doesn't vary too much from what it should, usually a digit or two; it stays pretty stable even on a deep coin. But the FE number can be MUCH higher than normal -- bouncing around all over the high single digits and teens, on a deep one. The problem with that is, there reaches a point with some iron targets -- most often a deep, rusty, bent nail -- where ID (and sound) starts to overlap with deep coin ID and sound. In other words, this kind of nail can register FE numbers pretty consistently in the teens -- down into the "deep coin" range. It's not uncommon for this type of nail to exhibit ID numbers bouncing around at 17-28, 19-29, 14-28, with a few 07-29 and 02-29 type of numbers thrown in. USUALLY, there is a small sector (say, 180 and 360 degrees) when rotating around this type of iron target where the FE number will more consistently read more appropriately high -- i.e. into the high teens and 20s, and the sound gets a bit scratchy -- the hint that it's a nail. But sometimes its a VERY narrow sector, with very little noticeable deterioration in sound or ID even in that small sector. The rest of the rotation around the nail, it sounds and ID's very much like a deep coin would. Again though, this would not be considered "wrap-around," correct?

Thanks for reading (if you actually made it through all of that!)

Steve



Edited 1 time(s). Last edit at 06/09/2015 03:53AM by steveg.

Excellent reading Steve,I just dug two nails this evening that had a depth reading of 6-7" but some of the 360 sweep was not as good as I'd want. Being that they were a bit deeper,I dug them anyway,hoping there was a coin down there that was on edge,sitting with something or some other third thing maybe. Nope. Two small rusty finish nails,that's all. On the brighter side I popped a 1918 wheat at about 7" so not all was lost. I'm really enjoying getting into this machine and threads like this really help everyone to understand the basics and beyond of what is going on(a lot of the time).

Kevin

Kevin --

Glad you are enjoying your new machine. I can only imagine how much you are going to like it as you continue to learn it.

When I go on a hunt where I'm intent of listening for deep, subtle coins, I will absolutely end up with a few nails in the pouch -- often those roofing nails, or else a bent, rusty one. Sometimes even a very rusty straight one with an enlarged "blob" of rust on it will fool me. It's not hard to hunt with an Explorer, once you know the machine, and never dig a nail. But, the "deeper" you hunt and the more you reach for the possible, "iffy," deep, fringe-type coins, the more nails will show up in the pouch. It's a tradeoff -- and for me, it took a long time on the machine, and a TON of nails dug, to begin to be able to recognize the subtle clues that a deep nail -- even a good-sounding one -- will usually give off, versus a deep coin.

Enough time on your machine, and I think you are REALLY going to love it.

Steve

Its normally caused by to much sensitivity. A good example of wrap arround is a hot rock steve. They scream in the upper right corner of an explorer. A CZ will do the same on rusted iron until u set the GB. Steve I highly recommend the book Digging Deeper With The DFX by Eric Foster for any one. Because of the many adjustment he goes into great detail as to how and why things work and it pertaines to about any detector.

In laymans terms I feel the ground that surrounds the target is loaded with various minerals which many or may not affect the target...
Metal detecting is not rocket science( no pun intended) so just get out there and swing and don't forget to smell the roses along the way...

While the explorer does have excellent I.D. ability its still not perfect...and yes iron will wrap around on an explorer..

And yes it will read like a Good target at times....esepcially the deeper targets..

When I run an explorer and dig real deep ..and I mean real deep past 12 inches.. all the target read the same nail wrap and coins and buttons it does not make a difference...they all read in the same spot...Even hot rocks....

What will be your clue will be the tonal quality of the target..

And if you want to dig super deep.. I want mention number becasue bpeople wont believe me.....Dont use a pattern....you never ever want the threshold to null...if it nulls you loose the audio edge..

I know some like to run a patttern and think they are digging the deepest becasue the I.d. is so good but its not, the open screen tonal quality is the deepest set up...and if you have a pattern the tonal quality is not there on the real deepies..

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla



Edited 1 time(s). Last edit at 06/09/2015 04:53PM by Keith Southern.

Which sounds would you recommend, normal,smooth, long or pitch hold.

dew -- never heard of that book, but it sounds like one I should read. There are so few good detecting books out there -- and if this is one, I'm game. I'll have a look on Amazon...

Dan -- I love this: "the ground that surrounds the target is loaded with various minerals which many or may not affect the target." LOL! Unfortunately, it's a true statement, and part of what complicates things, of course...

Mal -- I have always used normal, but that doesn't mean it's best for everyone. I can't advise on any of the others; what I can say is this -- I am a big believer that whatever you use, in terms of settings (ones that affect your tones), STICK WITH THEM over the long haul. My thought is, you want to train your ears to the sounds your machine makes, as it responds to various targets, and the best way to do that IMO is to give your ears CONSISTENCY, such that over time you begin to associate sounds, and the nuances therein, to what lies beneath the coil.

Keith -- I hear what you are saying, and I can see your point. I do not run a "pattern" per se, I run -- almost ALWAYS -- Iron Mask 22, which means that I am hearing everything EXCEPT any target whose iron reading is 22 or above. So, that's a pretty "open" screen, relatively speaking. I NEVER run a "coin pattern," or whatever, as it's too "restrictive" for me; I want to hear many more of the things in the ground than what a "pattern" would allow. BUT -- that said, I DON'T want to hear the barrage of nails, screws, rusty whatever-it-is objects, hot rocks, etc. So, my compromise is that I run the IM at 22. BUT -- I hear your point about not wanting to ever lose threshold; I can appreciate wanting to hear EVERYTHING -- which any null in the threshold sabotages. But, the only time I have ever run "fully open screen" -- i.e. no disc whatsoever, is when I am at a relic-type site, and I switch the machine to "Ferrous" sounds. I do this only rarely, and I'm not very good at it. One issue is, I have so many hours hunting conductive sounds, that it's not intuitive to run ferrous sounds, and I have to constantly "think" about the sounds, whereas in conductive it's much more "natural" -- as it's what I'm used to. With that said, though, in conductive sounds, I simply CANNOT discern, on some very small percentage of rusty, very deep nails, any tonal difference from a deep coin. There aren't many of these types that are nearly indistinguishable, but there are a few. However, what you seem to be saying is that there IS some tonal difference there, such that even though a coin, a button, a nail, a "wrap-around" target, whatever, may ID numerically (or through cursor position) in the SAME way, at the deepest depths, that there are still subtle tonal qualities that you can hear, that tell you to dig or not dig?

Keith, that is so far beyond my capability at this point. Do you do this "full wide open screen" hunting in Conductive sounds, or Ferrous sounds? I just can't imagine what you are hearing on a super-deep target (where everything IDs the same way, no matter the target) that lets you make a "dig" vs. "no-dig" decision. For me, there are times when I am digging deep, that I'll dig a nail that I think has a 75-80% chance of being a coin, such that it surprises me when I recover it and it was a nail. Likewise, I've dug coins that I was pretty certain were nails, and when they end up being a coin, I'm genuinely surprised. What I'm saying is, tonally there are times when trying to dig as deep as the machine will allow, that bent, rusty nails and coins can sound -- to MY ears -- nearly identical.

Can you elaborate at all on this for me?

Steve

Steve the DFX like the V3 allows a lot of adjustments so Jeff really goes into detail as to the how and why. There is just a lot of tech info most books dont have and knowledge about those things a detector does, which is automatic on most machines. I think youd like the book.

Hi Steve,

Yeah..."wrap-around" is a problem for metered machines. Not so much a problem for non-metered ones because they don't have displays that could potentially show "erroneous" information.

The Explorer XS was affected as was the Exp ll and the Exp SE. X-Terra's are also affected e.g the X-705 and to "get around it" ID 48 is 'blanked out' as a Default setting.
For E Trac, Minelab changed the x y axis to a Linear scale and put in the FE 12 line to minimise this wrap-around effect.

Des D

Thank you for your reply, I have used smooth, full sens, conductive for years, listening for that unique little sound of a deep signal. It can be reproduced in a test bed with trial and error. But it's a sleight sound in a orchestra of noise, knowing the soil and the machine is key. Someone finding a deep signal for someone else to hear is worth a thousand words.

I like to hunt in 2 tones All Metal when things aren't too trashy on the X-terra 705.
The spot I'm hunting at the moment when the 705 starts wrapping iron into the high tones, it is telling me: "Adjust Ground Balance Please".

A fixed spot on ground balance helps an awfull lot with the deep targets.

Des D Wrote:
-------------------------------------------------------
> Hi Steve,
>
> Yeah..."wrap-around" is a problem for metered
> machines. Not so much a problem for non-metered
> ones because they don't have displays that could
> potentially show "erroneous" information.
>
> The Explorer XS was affected as was the Exp ll and
> the Exp SE. X-Terra's are also affected e.g the
> X-705 and to "get around it" ID 48 is 'blanked
> out' as a Default setting.
> For E Trac, Minelab changed the x y axis to a
> Linear scale and put in the FE 12 line to minimise
> this wrap-around effect.
>
> Des D

HH
Johnb

Steveg What Keith says about the tone is spot on .
I have ran a explorer 2 for quite a while and the Ctx going on 4th year .
NAILS here is what I have found out using either machine ( roofing nails are very hard to tell from coins because as they sink the head starts to turn up because of the larger surface area now your looking at the head of the nail instead of a regular nail which most times is laying flat as you know round well give you the same signal no matter which way you attack it .Depth reading well be the same .
Now on a regular nail most are flat in the ground as they sink in time when scanning one way say north and south the nail will depth read say 12 inches but going east and west the nail well read 7 inches the true depth on the nail may only be 6 inches 3 inches or even 2 inches because of different size nails .
Coins well generally give a depth reading the same bought ways unless the coin is on edge or tipped a little but well still give #s closer together than the nail except a coin on edge.
Now nails that are really deep well read say 12 inches in a east west hit and the north south hit well also show 12 inches on the depth screen to bad the screen only go's to 12 but the audio on the nail well be silent unless it is a big hunker .
Bent nails that are bent in a U or V or L well read the same bought ways because the signal is the same bought ways as you know long items well give a different reading when hit from 2 different ways This is what I look for when I run into nails .
Now for short nails pieces of nails that is where tone well give you the most imfo .
But going back to Kieths statement about tone it is your # 1 clue if you have used the machine long enough and have dug enough crap things start to add up in the tone area ..
The depth differants helps in many ways when your not sure of the tone . sube



Edited 1 time(s). Last edit at 06/10/2015 11:33PM by sube.

Mal Wrote:
-------------------------------------------------------
> Which sounds would you recommend, normal,smooth,
> long or pitch hold.


Normal is to my liking for depth..

Smooth if Im in trash using conductive with the 4.5x7 installed..



Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Steve...

hunt-hunt-hunt..


Deep nails are tough..

Hot rocks are tough also on a wide open screen...

but at the same time a good target sounds round and a nail is elongated or Rough in report....And hot rocks have a monotone ring to them...just dead...

Conduct is the deepest mode especially on Buttons and low conductors..

Ferrous is the easiest to discern deep iron with in my opinion...

On an explorer I run it 32 manual sens... open screen no iron mask multi tone in either mode..dont use the filters...like deep or fast etc..leave them off...


the ground will beocme a NOISE a CONSTANT.. as will the iron....what you lsiten for is the SUBTLE BLIPS that's different from the NOISE..The multi tone allows for the nuances to be NOTICED..faint yet different on the deepies..


this guys in the parks digging those deep Silver coins dont look at the screen they listen to a caliope report and pick out a octave difference tone...

I know the Explorers have great I.d. but to get the most out of a Exlorer and open a site up its got to be ran HOT and OPEN and let your hearing be your master..

and the only way to do that is to just get out and spend hours running it like that..

if you say turn on the deep setting you mess up the nuances of the full report advantage of modualtion and tone quality blend..

You can run a Explorer straight out of the box safe and do well.. but if you want it to surpass especially in depth the language has to be learned

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla



Edited 1 time(s). Last edit at 06/11/2015 03:13AM by Keith Southern.

Thank you, will give normal a try for a while.

dewcon -- definitely sounds like a book I would enjoy reading. Thanks for turning me on to it.

Des -- appreciate the info; I'm not sure I understand, though, how "normalizing" FE to the "12" line on the E-trac helped to minimize wrap-around...

Mal -- abosolutely, what you said about "someone finding a deep signal for someone else to hear" being so important. That's a huge part of how I learned to hunt, and how I intend to teach my young cousin here in a few weeks. He's really excited about detecting, but is struggling. I've promised to help him out, and "finding good signals for him to hear" is how I intend to do so...

scoopjohnb -- interesting about ground balance being "spot on" minimizing "wrap-around." While the Explorer doesn't have adjustable ground balance, my Gold Bug Pro does, and I wonder if some of the reason I have so much trouble with square nails when hunting relics with that unit has to do with my ground balance not being "spot on..."

sube -- I'm with you, on the tones being so important. But, that "trick" you mentioned about watching the depth meter as another "clue" with respect to nails is interesting, and one I haven't considered...

Keith -- I am tracking along very well with most of what you are saying. Nails sounding elongated, and "rough" in tone, yes; some more than others, but yes...hot rocks with a "monotone, dead ring," yes, absolutely. I call it an "empty" sound...32 manual on sensitivity, yes; I always run 30 to 32 sensitivity...always multitone, yes; I always, absoltuely run maximum number of tones...no "filters," absolutely; I never run "fast" or "deep" on -- always off...AND FINALLY, I do hear you on the background noise and iron just being something to become "used to," and listening for "something different." I hear you on that, but I can't imagine doing that with a fully open screen, no discrimination whatsoever, in conductive sounds. Wow. I will give it a try, though, and try to learn it, as I DO believe that this would be the deepest way to hunt. I am "most of the way" there, I think, in terms of knowing this unit and running it "the right way." This last step -- fully open screen with no disc? Wow...but I am going to try it...

Thanks all, for the terrific help...

Steve

Steve,

In the Explorer Series most coins were detected on a 'tilted' line that curved diagonally across the screen from bottom to top right.
The main issue with the Explorer was it's [ Iron Mask ] feature didn't provide "accurate rejection" of Ferrous targets.
This was due to the fact that the Iron Mask adjustment and the "Coins Line" were misaligned.
It is that which was greatly improved in the E Trac.
The CO range had been expanded in the Explorer SE to accommodate a greater number of silver coins as prior to that many would show the same FE CO numbers.
So it's all to do with trying to provide a proper ID and improve ferrous rejection.

Does that explain a bit better?

Des D

Des D -- yes it does, actually.

I can see what you mean about the Iron line and the coins line being aligned, on the E-Trac, whereas they aren't, on the Explorer.

It's still hard for me to understand how "wrap around" occurs on the Explorer, since the Explorer has broken the return from the induced target current into two components (the "CO" and the "FE" ). Does wrap around become manifest in BOTH the CO and the FE? Or just the FE? And further, as I understand, the CO and FE are actually not really" conductivity" and "iron" measurments, of some sort, AT ALL, but instead or two components of the electromagnetic field induced in the target by the coil transmission -- I can't recall the components' actual names (something like reactive and resistive, I think? Like "X" and "R" or something?) Anyway, since I don't fully understand those terms (but wish that I did), it's hard for me to understand electrically what is going on.

That said, what you said about the Explorer vs. the E-Trac makes sense; I have a little experience on an E-Trac and I can see how, with the coins generally falling on the "12" FE line, that it makes more sense to run things like "two-tone ferrous" on that machine...

Steve



Edited 1 time(s). Last edit at 06/12/2015 12:42AM by steveg.