3/24/16 Survey: Halo Effect

Cant believe you guys let Tom off easy with a NO. No ....... lets hear why? Im a yes guy since i tend to see how that RUST forms and bleeds. This sometimes causes wrap around to a higher range pretty deep. Even copper pulls in a lot of minerals around it and can cause a heck of a crust when exposed to moisture.

Dew

Dew..... you are insightful (as I gave a 'lawyer' answer)......................... and tnss has provided the link to answer Dew's statement/concern.

Not to get too sidetracked here,,,but I would like to hear exactly what is changed when using the "Pf" process on F75.

And I will also comment,,, Why does it seem to me anyways,,,,Xp Deus actually seems to detect deeper on a freshly buried vs same/ similar target in undisturbed ground.
Yet seems Minelabs don't. Is the multifrequency they use the reason why??? This multifrequency can't get agreeable ( within limits) for a signal to be processed properly and provide a good signal --- as set out in the programming???



Edited 1 time(s). Last edit at 03/27/2016 01:14PM by tnsharpshooter.

The electrical conductivity of a target in relation to the surrounding soil would be greater if the soil were compacted. Certain soils tend to be more cohesive, and therefore denser with greater molecular attraction. Sand (med grains) is of average cohesiveness, and silt (small grains) can be compacted more than sand, clay (tiny grains) will have some of the best molecular attraction. Organic matter, such as forest floors, are not able to compact much and would have very little conductivity between soil particles.

Assuming there is water present with mineral ions present, it is reasonable to expect some enhancement of the eddies surrounding the non-ferrous target, assuming that copper, nickel, aluminum, or zinc ions have leached away. However, any eddies in the dissolved ion matrix surrounding the non-ferrous target would be exceedingly weak, short lived, and likely not register on a metal detector unless very near the surface (if even then). Near the surface the target's main signature would overwhelm any weak eddies that might surrounding the target. Non-ferrous detection would not be enhanced. However, loss of target structure due to corrosion of the metal surface, such as a copper coin thinned due to corrosion, would lose the ability to support deep eddy formation decreasing conductivity. Any patina within the copper coin's surface, or pitting due to metal loss, would also decrease conductivity and lessen eddy formation, which would make the target less conductive. The result might be a signal becoming more like non-ferrous trash. In addition, a shallow eddy in the target yields less information on the ferrous/non-ferrous nature of the target, likely lessening discrimination by the detector.

Now if the target were ferrous (nail), and the surface of the iron were wet (due to a moist soil matrix), the current driven on the target's surface should also be enhanced, perhaps enabling some of the oxidized iron surrounding the ferrous target, however weakly. The main signal from iron would not be from a halo but from the increased non-ferrous signature (appearing more like a conductive metal) due to a more conductive iron surface (electrons flow more freely). This effect in wet soil with iron nails present makes the ferrous nail sound more like a good non-ferrous target, which is not desirable. So, wet iron is bad when discriminating between iron and other metals.

If the ground were damp, with a compacted soil matrix, it is possible the primary magnetic field is directed more efficiently through the soil matrix, increasing detection depth. However, in highly mineralized soil (e.g., ferromagnetic minerals) where there are iron flakes, nails, and black sand deposits, these may act to spread the field horizontally to a greater extent, thereby decreasing vertical depth in damp, compacted soils.

So, the theory goes: Wet, compacted soil: nails sound more non-ferrous. Highly mineralized soil: loss of depth. Low mineralized soil: increase in depth. Non-ferrous targets would not benefit electrically but would oxidize faster, losing mass, and be harder to detect.

Well thought out post JA

So many variables.
PH of soil, Acidic soil Ph 7 and below with hydrogen ions present
Size of soil particles (sand, silt,clay) also determines the amount of water and oxygen present.
Amount of organic matter present, <1% - 10%>
.

Less snapshot's in PF mode..so the slower changes of soils are not as noticeable as the quicker changes of a Metallic target..

Soil that get's plowed can cause say clay to come to the top layer and loam to go below and also just create a Jambalaya type dirt soup,,

DE Mode does sample-sample- sample-sample-report...

PF does s---a---m---p---l---e---s---a---m---p---l---e---Report



Keith

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

Johnnyanglo Wrote:
-------------------------------------------------------
> The electrical conductivity of a target in
> relation to the surrounding soil would be greater
> if the soil were compacted. Certain soils tend to
> be more cohesive, and therefore denser with
> greater molecular attraction. Sand (med grains) is
> of average cohesiveness, and silt (small grains)
> can be compacted more than sand, clay (tiny
> grains) will have some of the best molecular
> attraction. Organic matter, such as forest floors,
> are not able to compact much and would have very
> little conductivity between soil particles.
>
> Assuming there is water present with mineral ions
> present, it is reasonable to expect some
> enhancement of the eddies surrounding the
> non-ferrous target, assuming that copper, nickel,
> aluminum, or zinc ions have leached away. However,
> any eddies in the dissolved ion matrix surrounding
> the non-ferrous target would be exceedingly weak,
> short lived, and likely not register on a metal
> detector unless very near the surface (if even
> then). Near the surface the target's main
> signature would overwhelm any weak eddies that
> might surrounding the target. Non-ferrous
> detection would not be enhanced. However, loss of
> target structure due to corrosion of the metal
> surface, such as a copper coin thinned due to
> corrosion, would lose the ability to support deep
> eddy formation decreasing conductivity. Any patina
> within the copper coin's surface, or pitting due
> to metal loss, would also decrease conductivity
> and lessen eddy formation, which would make the
> target less conductive. The result might be a
> signal becoming more like non-ferrous trash. In
> addition, a shallow eddy in the target yields less
> information on the ferrous/non-ferrous nature of
> the target, likely lessening discrimination by the
> detector.
>
> Now if the target were ferrous (nail), and the
> surface of the iron were wet (due to a moist soil
> matrix), the current driven on the target's
> surface should also be enhanced, perhaps enabling
> some of the oxidized iron surrounding the ferrous
> target, however weakly. The main signal from iron
> would not be from a halo but from the increased
> non-ferrous signature (appearing more like a
> conductive metal) due to a more conductive iron
> surface (electrons flow more freely). This effect
> in wet soil with iron nails present makes the
> ferrous nail sound more like a good non-ferrous
> target, which is not desirable. So, wet iron is
> bad when discriminating between iron and other
> metals.
>
> If the ground were damp, with a compacted soil
> matrix, it is possible the primary magnetic field
> is directed more efficiently through the soil
> matrix, increasing detection depth. However, in
> highly mineralized soil (e.g., ferromagnetic
> minerals) where there are iron flakes, nails, and
> black sand deposits, these may act to spread the
> field horizontally to a greater extent, thereby
> decreasing vertical depth in damp, compacted
> soils.
>
> So, the theory goes: Wet, compacted soil: nails
> sound more non-ferrous. Highly mineralized soil:
> loss of depth. Low mineralized soil: increase in
> depth. Non-ferrous targets would not benefit
> electrically but would oxidize faster, losing
> mass, and be harder to detect.

Yep,that's what I said...lol

------------"Cz's still bad to the bone".------------
Living on a big ass Astroid.
The woman that got my rib,I want it back.

Sorry for not being a one-word answer:

Here is a curious related effect: As you probably know, we have a lot of coke (part-burnt coal) in our European farmland. In dry ground, it's not so troublesome, but the wetter the ground is, the more the stuff 'comes alive'. Yet it has no 'halo', it doesn't react/decompose like metals. But somehow, when wet earth is in contact with it, it is enhanced. Now this may be because it gives a weak signal anyway, and so any improvement is significant, compare this to real metal, where the metallic 'good conductor' response dominates, and if there are currents circulating in the surrounding 'contaminated ' ground, they only contribute a trivial amount to target visibility.

Also bear in mind that physics means that target signal strength diminishes very rapidly with depth. The net result is that even if a target had a 10% 'enhancement' due to a 'halo', that would equate to less than 2% perceived depth reduction.

And, off-topic: Regarding: "what is changed when using the "Pf" process on F75."
The answer is detailed in one of Dave Johnson's Technical papers on Fisherlabs website.

“plowed field process” replicates to some extent the characteristics of earlier all-analog “two-filter” discriminators. It lacks some of the performance enhancements which software-driven signal analysis made it possible to incorporate into the default and jewelry processes. Lumpy ground .... tends to negate the benefit of those performance enhancements, making it possible for some users who are familiar with the response characteristics of traditional “two-filter” discriminators to put that familiarity to use, to get slightly better results in lumpy ground.
From memory, DE process auto-switches between two filters as it sees fit, based on how wobbly the ground signal is. This makes me think that if you used the machine on a plowed/ploughed field, DE mode would auto-select PF behaviour anyway. You would be more likely to see a difference on flat ground, like a grassed park.



Edited 1 time(s). Last edit at 03/28/2016 12:25PM by Pimento.

I used pf mode a fair amount in both fields and stable ground. It seems to key on peak signal strength.. Hence more iron falses that require a re-sweep of the target. Fortunately a single sweep from the opposite direction correctly ID's the target as iron while non-ferrous gives a repeatable signal. Actually, it did a good job of locating deeper co-mingled with iron targets in lawns, at least for me. Slow going in old iron infested areas but productive.

Yes on copper and nickel not precious metals like gold and silver. Because they leach into the ground after time where a precious metal won't. JMHO.

Dave J. had this to say back in 2010 about coal/coke and metal detection:

Wood fuel contains very little iron, and the ash usually contains only small fragments of charcoal which although electrically conductive, are small and so don't usually cause too much grief with metal detectors. In the short run the wood ashes when tossed out are electrically conductive but over time, rainfall leaches the conductive ash minerals away. In drier climates the leaching process may take decades or longer, but in such cases the soil is dry most of the time so the minerals (in their dry state) are not electrically conductive.

Back East, not only wood, but also coal and coke have been used for household fuel. Coal is dirty stuff but where it's available, it's cheap. It contains iron minerals which the burning process reduces to metallic iron or to magnetically active reduced iron oxides. And, as it burns it turns some of the unburnt coal into coke, which is a lot more electrically conductive than charcoal due to its higher density. When the ashes get thrown out you have a mixture of magnetic iron minerals, highly conductive coke residue, and ash minerals which are electrically conductive when wet. Over the course of decades, an area where stove and furnace ash was dumped can accumulate a lot of stuff that drives metal detectors nuts, yes even PI machines. In the humid East (USA) the conductive ash minerals eventually leach away but the iron and iron minerals remain in place, often converting to the even more notorious maghemite (red rust), while the coke is chemically inert and will remain in the soil. Freeze-thaw and other soil mechanical processes may eventually break the stuff up into smaller fragments, reducing its electrical conductivity, but that probably takes thousands of years or longer.

And then there's coke. Coke is fire-roasted coal, just as charcoal is fire-roasted wood. The primary purpose of converting wood to charcoal is to drive off the hydrate to make the fuel lighter and more compact and thus more economical to ship. The primary purpose of converting coal to coke is to drive off sulfur and other impurities so that the stuff can be used to smelt iron and a few other metals, and (in the bad old days) to generate "producer gas" for industrial and municipal fuel use in the same ways that natural gas is used nowadays.

In other words, charcoal is produced for use in primitive economies and coke is an industrial product.

In regions where coke is produced, it usually is (or has been) made available as a fuel for household use. For household use it is preferred because it is denser and burns cleaner. Because coke is a high-grade fuel, higher grades of coal (if available) are used to produce it, and therefore coke is usually lower in iron and ash impurities, although the iron smelting industry does not regard the iron content as a nuisance, only the ash.

When household coke ash gets tossed into the back yard, the problems from a metal detecting standpoint are basically the same as those of coal ash (clinkers, cinders, etc.) With coke fuel residue, the biggest problem will usually be unburnt pieces of coke, which are so highly conductive that large pieces can register into the high coin range on a metal detector.

In the humid East, people often dumped their ashes in the vegetable garden or fruit orchard, since the soils are deficient in calcium and other minerals which are present in ash. Ash was used as fertilizer. Sometimes it was dumped into the privy. And sometimes it was just dumped into an ash-heap which may have also been the compost and manure heap. Finding lumps of electrically conductive unspent carbon fuel may not be your favorite beep, but knowing why the stuff was dumped in certain places and not in others can help you decipher the site use and lead to more productive beeping.

Some sites are literally blanketed with such miserable stuff. This is because coal and coke are used on an industrial scale and the spent fuel is discarded on an industrial scale. Iron and other mineral smelting operations also produce large amounts of silicate mineral slag which is usually high in magnetically active reduced iron minerals. The stuff gets piled up until someone figures out how to get rid of it. It is usable as landfill aggregate and being cheaper than natural aggregate (because someone wants to get rid of the stuff) it does get used as landfill aggregate. Say for instance there's a hilly area where you want to put a baseball diamond. You need cheap fill material to create a large flat land surface. You use industrial waste aggregates as the primary fill material and mix some topsoil into the upper layer so the grass can grow. It's not a wicked plot against beeperists, it's just a good way to build a baseball diamond if industrial waste aggregates are available.

For those interested.

I was wondering if the leached iron oxides around ferrous objects or the leached metals around copper, nickel or zinc might be seen as an increase in ground mineralization by the detector causing the ground around the object to be slightly to the positive side of you GB settings (thus your GB is set to negative) while not strong enough for your detector to signal on.

That combined with the conductivity readings of the actual target might make those objects with "Halos" more detectable, especially when the ground is moist.

It would be desirable for good targets and makes things worse in iron.

I have no idea if that's what really happening though. It's just a theory

HH
John



Edited 5 time(s). Last edit at 03/29/2016 05:25AM by DirtyJohn.

Thanks for posting that John, good read.
We have 'clinkers' all over the place here in SE PA. I call them hot rocks for the lack of real fact. And yes they do mostly read mid to high tone on f-75 or a cz. Some are a dull porous black....some are shiny high gloss crystal black, like coal.....they will set off a pinpointer and yes they are a PITA.

There is info concerning this subject of halo in this read,,, actually many good topics discussed here.
Folks who are beginners---- need to read at least some of this good read.

[www.dankowskidetectors.com]

Here are the results:

Yes:14(including myself) No:7

So what can we tell from this small sample of data? It's nearly two out of three, or 66%, believe there is a halo effect.

My opinion coupled with the experiences I have had, do verify that a halo effect does indeed exist. However, silver gold, and nickels(I have had a hard time finding deep ones) to some extent, have halos that are not effective enough to make any difference in finding them.


What I find interesting, is iron falsing. The fact that ions from iron, leeching into the ground mimic silver in conductivity, is a very unique!

Yes

Hi,,,,Yes & double yes I can't seem to follow directions/instructions so please let me elaborate on this very controversial subject....If you listen to the experts they say no to coins etc. but say yes to iron....I really think these armchair experts need to get out more and do some serious detecting then formulate an accurate opinion....The expert opinions with a no answer that I have read about have performed their tests in a laboratory environment.....You can't duplicate an action that may take up to 100 years plus to take place in a controlled lab and come to a definitive/conclusive answer yes or no....Everyone here has the right to their own opinion and base their answer on what they have learned out in the field....

Here's how I base my unequivocal YES answer....If anyone has read any of my past post you will see that I have little to no problem getting 100 plus Injun's a season....This feat does not come by accident, it comes on my ability of taking advantage of the halo effect....The halo effect I'm talking about mainly applies to Injun's in the correct soil matrix combined with the correct moisture content....If the EMI is at it's lowest and the correct moisture content is available plus the angle of approach is correct,this is when and where the magic will seem to happen....I know a lot of you will give credit to a new coil or machine when you hit a depleted coin site and pull a few more coins out,but in most cases it is the combination of the above factors....This is what I believe that is taking place on a halo effected coin....Many times I will get a definite deep Injun signal... I will then open the hole/plug only to find it's gone or the signal gets super weak....What I believe really happened is, I broke the halo effect and the coin is way deeper than I anticipated....In a nutshell (example only) if a coin is laying at 10 inches and it has a 2 inch halo surrounding it, I was actually hearing the top of the halo at about 8 inches and not the coin itself laying at 10 inches....Also worthy of mention is the soil surrounding the coin will be green,usually moist and is easily heard by the detector too....The halo affected soil seems to come alive with noisy enthusiasm....

If I had video recording capabilities perhaps I could demonstrate this phenomenon....Keep in mind that these same Injun's will read out whatever they want to on an ID machine....You can simply throw your air tests and nail board tests out of the window when your doing about 80 mph down the highway on this one....These hidden Injun's speak their own language and sometimes speak with a forked tongue or duplicitous manner, so beware.... For you Doubting Thomases, if this is not a halo effect then what would be the correct name be for this almost immutable phenomenon?....Respectfully yours....JJ

jimmyjiver Wrote:
-------------------------------------------------------
> Hi,,,,Yes & double yes I can't seem to follow
> directions/instructions so please let me elaborate
> on this very controversial subject....

JJ, you're back! Did you get time off for good behavior? <g>
Well written and informative comments. Thanks.

Wayne

Pleasant Garden, NC
AT Max, Nokta Impact, MX Sport, Nokta FORS Relic, GPX 4800, Infinium, Racer, Deus, F75SE, Nautilus DMC II (order of acquisition, last to first)

Does an archeologist argue with a plow? A bureaucrat with a bulldozer?

Well,, my additional thoughts here.

I truly think folks for the most part are confusing " when all the stars and planets" are aligned indeed for halo.

Things like ground moisture differences, changing ground mineral levels ( to maybe lower), EMI, the detector, the coil, how the target is swept speed wise, and position wise.

I don't think there is really a way to prove--- other than just opinions.

I guess a person could bury an ole IH in a moisture proof nonferrous wrapping bury down to 10",, and bury another without the wrapping ( unprotected)) and then go back in 150 years and check them--- to see the differences if any.

If a person read some of what has been said here,,, would it be a fair statement to say,,,,coins buried for 125 years would in fact be easier to detect vs the ones buried for only 75 years.

I guess what I'm leaning to is,,, sounds like some of the deeper -- assuming sink rate,,, would infact be buried longer and on average be older,,,hence locating them would be easier or the same from a detecting standpoint --- if you believe in the halo affect.

Or maybe a better way to say,, assuming a coin hits rock bottom on sink rate--- won't sink any more,,,but is currently just below depth detectable depth,,,,so with time,,,, putting halo effect into the equation,,,this coin once undetectable--- can someday be detectable,,, this later being detectable having nothing to do with detector technology or additional detector capabilities.

So maybe we are better off just laying off our sites,, and buying newer model machines and coils---- instead just wait 40 or 50 years and go back and find the coins with our older machines..lol



Edited 6 time(s). Last edit at 04/06/2016 09:41PM by tnsharpshooter.

Some additional data,, or food for thought.

The 2 IHs I dug below,, both first generation types,,one on the left,,a 1902,, the other date unknown.

They were dug at different locations,,,the one of the left came from approx 9" " deep,,the one on the right came from approx 6"-7" deep.

I got curious and done some measurements/ weights on both using a digital fireame reloading scale, and a digital caliber.

Btw both coins just rinsed with water after dug, no medium to hard rubbing or cleaning.

The better looking Indian,,,
Weight....2.77 grams or 42.8 grains

While rotating coin checked both thicknesses and diameter

Diameter ... A good consistent .750-.751

Thickness ..good consistent .054"

The not so good looking IH
Weight...2.41 grams or 37.2 grains

Diameter... Ranged from .737-.744"

Thickness..Ranged from .050"- .052". depending on coil position in the jaws of micrometer.

Big MAYBE for iron only, Absolutely NOT for silver, gold, and copper

Pinpoint twice, dig once

ncwayne Wrote:
-------------------------------------------------------
> jimmyjiver Wrote:
> --------------------------------------------------
> -----
> > Hi,,,,Yes & double yes I can't seem to follow
> > directions/instructions so please let me
> elaborate
> > on this very controversial subject....
>
> JJ, you're back! Did you get time off for good
> behavior?
> Well written and informative comments. Thanks.
>
> Wayne


LOL

He's baaaack!

What up JimmyJive!?

And some additional thoughts on the subject.

Here is one thing I''ve not seen talked about much on this forum.

This corrosion or leaching of a coin while buried that takes place.

What about the change in shape that could take place,,,, for example if the corrosion takes place on a coin laying flat in the ground,,, wonder if the coin while corroding or leaching becomes " dished" in shape?? Would this possibly enhance detection???

And since JJ brought up the ole IH,, IHs are actually made up of different metals,,,,, now just how consistent were the metals mixed in the IHs,,,, and could this corrosion, or leaching actually expose from a higher percentage say the copper vs the other metals,,,, hence make the coin more detectable--- depending on the detector ( frequency used).

I had a war nickel for example while buried hit 12-40 on the etrac's screen,,.,thought it was a silver coin,,,after digging and laying war nickel on the ground and sweeping--- solid 12-13/12-14.
The etrac evidently at one time saw this mix of silver in the subject war nickel.

Hi,,,Wayne & Wayne, thanks for your reply...I have been designing a new metal detector to handle and meet my needs around here....I'm also working on designing headphones to meet my needs.. I hope to wrap these projects up in less than two weeks from now .....I tend to also limit posting anywhere anymore because it gets to confrontational when I do....There's to many Chiefs and not enough Injun's ..LoL.....Hey TSS, you seem to over think things and complicate them at the same time.....But I do applaud your thinking process........JJ



Edited 1 time(s). Last edit at 04/07/2016 10:25PM by jimmyjiver.

JJ,
Metal detecting is a thinking hobby or sport..,, at least to me.

Not trying to play big dog,,, just introduce a few things here,, I think do and can play a part.

Maybe the BIG dog here will weigh in on some of my over thinking.-- you call it.



Edited 1 time(s). Last edit at 04/07/2016 10:27PM by tnsharpshooter.

No

Hi TSS,,,,I was not even talking about you or your comments so I edited my last statement....Now you see what I mean about being confrontational not educational on here....I have to defend myself all the time on here.....I probably forgot more than most people know....I think I will just kick back and just grin a little while reading miscellaneous collaborations about metal detecting and the one that got away....Later........JJ

I certainly did not attack you JJ.

I do disagree with folks here sometimes,, I also try to add I think valued added information.

I may not be the smartest stick here on this forum,, and besides I didn't realize it was necessary here to be a Menza member to contribute or be an Einstein.

I do have a pretty good memory too.

There are IMO some very intelligent folks here that do read and post.

It's not about who's the smartest or who has forgot the most vs someone else,,, rather just good ole conservation.

A meeting of the minds--- "So to speak"

Besides, remember,,,, it is the metal detector that really does all the work-- we as users just need to learn to interpret or interpret better.



Edited 2 time(s). Last edit at 04/07/2016 11:01PM by tnsharpshooter.

Hi TSS,,,,I hear ya,,,,I think you never stop learning and when you think you know it all you probably bumped your head....I was having a Trump moment and thought everyone was out to get me....LoL.........JJ

I am actually glad to see you back posting, JJ.
Missed ya.

The more folks who can add here to the potion of detecting the merrier.