Seeking help to understand "wrap-around" and how to use it to possibly improve your detecting...

I have heard folks talk about "wrap-around targets" -- but don't understand what that is. I saw dewcon refer to that in the ongoing CZ-3D thread. I think I understand it to be something about iron "wrapping around" -- from an ID perspective -- into the "high-tone" or "high conductivity" range. Can some one help me understand first, if my vague understanding is correct, and second, what is actually going on in the

Thanks all,

Steve



Edited 1 time(s). Last edit at 07/15/2011 07:36PM by steveg.

You may want to ask that on a V3I forum their machine can be programed to use wrap around

LowBoy

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Lawrenzo --

Thanks for that...if I don't get an explanation of how that works here, I will. I know I have heard guys refer to "wrap-around" referring to Minelab Explorers, and I would like to understand better what that means...

Steve

Hmmmmmm.........This could (and should) go two directions. I'll sit on the side-line and watch!

I assume referring to masking and hope a learned forum member perhaps adds his interpetation..

Cause its you Mr. Steve......lol.........I will try to explain this.

Draw a 4" straight line........on the left end of line put a -95......on right end put a +95. In the exact middle of line....put a 0. This is your VDI/TID range of the detector (White's detector VDI ranges are used for this explanation).
0 to -95 represents ferrous/ground mineralization readings.
0 to +95 represents non-ferrous/hot rock readings (+95 is a hotrock)

Now......here is a little explanation of how a deep coin reacts with a VLF machine:
"a coin can read higher than normal as the result of the ground conditions. The detector, in analyzing the signals, adds the ground signal to the target signal. There is a tendency for some objects to read upscale on a target ID detector in highly mineralized ground. As the target signal becomes weaker and weaker, the ground signal begins to dominate, thus the higher than normal reading from a really deep coin.

Because of above phenomena, a deep coin can possibly register as a Hot Rock. So on a White's machine, accepting +95, also accepts these deep coins. Because the high mineralization can overshadow the deep coin, a deep coin can read as a -95, -94, -93, -92 etc. Normally these ranges are reserved for the ground mineralization/very large pieces of iron, in the eyes of the White's detector. Thus the term 'iron wrap-around". A more accurate term would be "ground mineralization over powering target".

Some White's users will set machine to accept +95(hotrocks) and -95 through -88 or lower, to prevent the deep coins from registering as hotrocks or ground mineralization/large ferrous items. So a White's user will get a audio signal on these +95/negative VID numbers instead of no audio signal if they had not accepted these settings.

Its a matter of playing the odds. If its a park, and there are little to no large chunks of iron, then little if any -95 thorough -88 or lower readings are going to be large ferrous items, but they may be ultra-deep coins.

Lastly, the straight linear line I had you draw at the beginning, is actually a circle, as there are no 'end' points in reading ferrous/non-ferrous items. It all flows together, thus the cross-over effect.

Hope this helps and can be applied to your Minelab Explorer.

p.s. I forgot to add, a hotrock signal can be verified by using the 'all metal' mode. Most hot rocks will not produce a audio signal when scanned in all metal mode.



Edited 4 time(s). Last edit at 07/14/2011 08:26PM by TerraDigger.

Yikes!!! Tera, whered you pull that from? My head hurts.

TD.... you explained that MUCH better than i could have. How ever... i used to run my DFX NOT accepting that +95 which would sometimes bring those deeper coins out of the negitive range..... or reduced the sensitivity a bit. You are right it has a lot to do with weak good signals getting over powered. You can see the same affect with the Explorers as well.... just listen to the tone of a very weak coin that has been in the ground a long time. Those signals get processed.... and what is spit out is bounce... and a smartscreen leaning clearly to the far left. Unlike when i used the DFX i find the tone of the Explorer will lead me more toward digging these targets. I still disc ONE tiny spot in the upper smartscreen with the SE which in the field helps break up those hot rocks. The only target ive found that SOUNDS like a hot rock is a large cent. Everything elce.... even iron is just different to me. Dont get me wrong.... i dig some really deep square nails also. There is just that point of the circle where the high conductivity of a coin will make it read higher.... since there isnt any higher it goes to the negitive on your TID. Now ill wait for Tom to educate me again of course

Dew

Its actually the observations of many detectorists over the years. All credit to them. But it is one of the cool things a White's VLF detector can do (and I suspect other mfg's too).
Dewcon........your tips will help Steve alot......I think he owns the SE Pro.



Edited 1 time(s). Last edit at 07/14/2011 09:43PM by TerraDigger.

Good examples...I would like to add my thoughts which may or not be scientific or even true.
This wrap-around is the product of high conductive signals received by detector...usually... but not only high conductive signals.
Iron seems to produce a spectrum of conductive signals...especially if it has been underground for a while.
Nails exhibit this in that they should always read low on scale but have spiked high conductive signals to go along with the low.
My guess is when the coil is swept and is coming off or approaching the end(s) of the nail(s) can produce the high conductive spike.
Then the angle of approach of the sweep of the coil can cause the falses to be either more or less.
Of course shape/size of the object comes into play as well as ground signals.
My other guess is almost all detectors are more or less subject to these wraparounds.
The detectors that are least effected by this is either influenced by a heavier dose of discrimination and/or heavy filtering.
The multi-frq detectors such as the CZs and Explorers seem to suffer from this wraparound....maybe more than most other detectors?
....Hmm, not sure about that since I have used a host of single frq detectors...if I used low discrimination...you can hear a lot of false positive signals....
or at least broken signals that should indicate the presence of a high conductor...but it was a nail......

So in short my theory is that iron (mostly in the form of a nail but not limited to a nail) produces a spectrum of spike signals....
not only are they in the higher conductive range...it even reaches in the mid frqs but to a lesser extent and mostly goes unnoticed.

Wrap-around usually means a 360 degrees...like a circle....when we generally think in terms of a 180 degrees...
So...is it a true wrap-around or...what we are experiencing is a detector's reaction to a spectrum of spike signals....
............or is it both?
In the end it comes down to telling the good signals from the bad...which can sometimes be very subjective.

We need Super Dankowski for further illumination.

This played out well. SteveMS....you are right on target. Good depiction.

Good one SteveMS. I guess all targets are just spikes on a graph that are being interpreted based on the processor. I know ML calls theirs Con and Ferr readings.... yet clearly those Ferr readings arent really the amount of iron in a target. Ive always felt it was more the rust that confused the machine than iron. I know i know rust is iron.... but in the fields where you get a LOT of hot rocks here in Indy, if you switch to Ferr on the ML you still get those high tones... but they show in the lower left which to me shows some of this wrap around thats happening by staying on the high end regardless of Con or Ferr setting. Must be the oxidation causing these spikes.

Dew

Guys --

Thanks for the great info, everyone. Great answers and they are much appreciated. I need to think about and absorb -- re-read all this thorough info...

So, when you hit a small rusty bolt, or a bent nail, which is reading very high on the conductive scale, is it getting "wrapped around" from the iron end of the spectrum -- which should be the low conductive end? In other words, when I sweep a signal that reads, on my Explorer, low on the ferrous side and high on the conductive side (the opposite of what it should), then is this a "wrap-around" iron signal?

There are times when I hit OTHER iron objects, not rusty bent nails or small rusty bolts with washers, that DON'T sound as much like a coin. Instead, they DO read 31 on the conductive side, but it's a different sound, a flat, almost "hollow" or "empty" sound. Yes, it's a high pitch, but it sounds "different." Are THESE "wrap-arounds" from the iron end?

Steve



Edited 1 time(s). Last edit at 07/15/2011 07:36PM by steveg.

Food for thought. Some examples.

I was hunting in my usual mineralized sites with a CoinStrike. Found a nice deep dime around the 8" depth mark. It gave a nice high tone and a TID reading of 42. Trouble is that dimes usually read with a TID of 28 on a CoinStrike. What kind of tone and TID would I have gotten if the Coinstrike's discrimination range stopped at a TID of 38?

I was hunting in my usual mineralized sites with a Whites V3i in the 7.5 hKz mode, coin ranges accepted, all ferrous ranges rejected. I was eyeballing a coin on the ground that the detector wasn't reporting on. Totally silent. Why was the detector totally silent on a coin on top of the ground?

I was hunting in my usual mineralized sites with a Whites DFX. My disc pattern accepted all the high conductive numbers up through +95 and included -95 through -90. All the quarters I found at this site gave an iron grunt and read with -93/-94 TID numbers. Why was I getting iron grunts and negative TID numbers?

Take your detector, set it to minimum disc, get some highly conductive targets and start air testing them. One silver dollar by itself should sound off properly. What happens if you take two of them and hold them very tightly together so that they appear as one target to the detector? Do you still get a high tone or is your detector silent? Or did you get some iron grunting?. If you got a normal response, add another high conductive object ( a nice size silver ring works real well). Hold them tight enough that they respond as a single target (the current flows through them as one target) At some point your detector will quit reading the object as a high conductive object because the conductivty has surpassed the detectors high end discrimination range and begin reading and sounding as if it was a ferrous object.

In the real life examples above, ground mineralization raised the objects conductivity (changed it's phase angles so that it looked as if it was a higher conductive object) and the detector's report was based upon the circuitry's high conductor limits. Once the target excceeded that range, the detector read the object as a ferrous target and reported or not reported based upon the discrimination settings in use.

That is what is what we call "target wrap" or the "wrap around effect".

HH
Mike



Edited 1 time(s). Last edit at 07/15/2011 09:25PM by Mike Hillis.

My explanation/Dewcon's is oriented to finding ultra-deep coins (improve your detecting) by adjusting the disc/sens. The other posts are a better technical explanation of the wrap-around effect.



Edited 2 time(s). Last edit at 07/16/2011 12:39AM by TerraDigger.

I think Jeff foster explains this very well in his books for whites machines.

For me it means alot when thinking about losing high conductive targets that wrap around and signals as a iron target close to the gb setting or become silent.

Iron that wraps up into high conductur isnt really wrapping i think. The permeability and magnetic properties of iron makes it conductive target.

I found a vid that i like that shows the wrap effect on the etrac.



[www.youtube.com]



Edited 1 time(s). Last edit at 07/16/2011 03:23PM by frnifo.

Hummm GB. Kind of makes it sound like its more of a figure 8 that a circle. Because the whites GB ( think) is somewhere around the 0 salt setting on that 190 scale. So if the GB and -95 to +95 are tied together.... sounds like a figure 8.

Dew

Best explanation i have seen is a wheel.

Salt is conductive and ranges from + 1 to + 6 on whites 100 id scale.

If you obtain a balance in the salt region you are far away from high condutors so you will get them very deep and they wont wrap to the other side of the gb setting. Small nuggetts can be invisible together with small foil bits and earknobs and coke.

The problem with silver wrap is when the balance point is closer to normal setting - 93 - -94. Then high conductors may wrap around the gb setting and become invisible or iron humm.

I do believe that the explorer series operates with a preset gb setting in the salt region and the etrac in difficult is the same. With the etrac in neutral you operate with ur gb setting around - 94.

Therefore as the vid shows. The same type of fault as the first gb se s was found to have.

But the etrac should be much more responsive to coke and small gold in neutral gb setting.

Great Post here guys! Love the great info!

It's what happens when a person is extremely dissatisfied with his detector and there is a tree handy

Sorry, could not resist.

Jerry

Good one Jerry , It also goes for golf clubs

Interesting topic and very informative....thanks for postin'.

July 20, 2011
July 20, 2013
Synchronicity?

As always, very thought provoking discussions.

Wrap Around

NASA-Tom Wrote:
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> July 20, 2011
> July 20, 2013
> Synchronicity?

lol, quite a coincidence.

You saw it because your trained to see patterns more then the average person. But humanity in all have better understanding of symbols and recognition of patterns then we have with the use of letters and numbers. We want all the info we can get on a screen but with to much letters and numbers we get confused more then informed. With a symbol we will hear with our eyes.

Im working on a symbolic information screen for detectors that will give the detectorist two more ears. The eyes. As a human You can easily hear several different sounds but you will have trouble reading two books at the same time while doing a physics calculation. Symbols fix that problem.

Instead of fooling brains, screen information can be made to feed brain with usable information to interpret. All in one symbol on a color screen that will hopefully boost visual hearing where acoustic hearing is low or have high possibility of being missed..

Pulse detectors also. Best on Mixed mode detectors though and if hybrids is allowed in the future ( vlf/pulse) it will work excellent

Well, if someone likes it beside me, lol..

ozzie Wrote:
-------------------------------------------------------
> Yikes!!! Tera, whered you pull that from? My head
> hurts.



LOL!