On my mind -- Random Thoughts

Carl.......... understood. Thanks for responding. While we are on this subject . . . . . . in regards to the principle operation of a PI.... is it possible, when the transmitter is off (receive cycle)......... to take 2 samples (or more) of the electromagnetic (EM) hysteresis decay rate (only eddy response). Compare the two. Analyze the decay time-domain ramp-down...... so as to analyze the (large) difference between paramagnetic, diamagnetic and ferromagnetic permeability/susceptibility time-domain ramp-down of these 3 different types of metals. In my non-calibrated ears...... there is a highly measurable differentiable/delineable audio length duration between (especially) a diamagnetic vs. ferromagnetic substance/target. I'm uncertain if there would be a requirement for an accelerometer. In this case, I speculate not. . . . . . as ..... simply the 'difference' between the two duty-cycle receive samples, , , , , , , especially with the large energy decay ramp-down (or zero hysteresis)....... is a 'tell-all' signature emitter........... stand-alone.
Diamagnetic materials have virtually no magnetic susceptibility/permeability; subsequently, no hysteresis. Ferromagnetic materials are on the opposite end of the spectrum....... with maximum magnetic susceptibility/permeability......... (posing a large decay ramp-down). Can today's rapid microprocessors 'see' the difference.

((( Not sure if this is Minelab's MPS Multi Period Sampling ))).

I have mentioned all of this data many years ago; yet, hoping to (this time) possibly jaunt/strike a light bulb (epiphany)......... for............ once-and-for-all............. a technological breakthrough (that will benefit mankind).

It's not a matter of "IF"; rather, it's a matter of "WHEN"

I am so very impressed with all the knowledge on this site!!

huh??? parmagnetic...diamagnetic...etc?????????????????? I'm in awe.

He lost me at "Carl".....

Same at Carl... but I hope he keeps at it. The final outcome, no doubt will help many. Wish I knew a % of what he has forgotten over the years much less what he has retained lol

Some good info. Maybe here's a place to start. What technically is going on with Garrett ATX with iron check feature??? I realize some say it's depth limited on its accuracy/reliability. Is this the start of a PI's ability to distinguish ferrous and nonferrous materials, and with further advancements could it be someday be made more reliable and correctly distinguish deeper targets????

Currently....... I am (somewhat) performing this tangentially. . . . . . by virtue of finding a target and memorizing it's audio length/duration. Then................. I implement/interject a large increase pulse delay (jumping from approx 8.8uS to 25.0us) via the adjustable pulse delay control. . . . . . . then.....re-sweep the target....... looking for a change/delta in audio length duration. This is a band-aid/old-fashioned way of audibly looking at hysteresis/permeability.

NASA-Tom Wrote:
-------------------------------------------------------
> Carl.......... understood. Thanks for responding. While we are on this subject . . . . . . in
> regards to the principle operation of a PI.... is it possible, when the transmitter is off (receive
> cycle)......... to take 2 samples (or more) of the electromagnetic (EM) hysteresis decay rate (only
> eddy response). Compare the two. Analyze the decay time-domain ramp-down...... so as to analyze the
> (large) difference between paramagnetic, diamagnetic and ferromagnetic
> permeability/susceptibility time-domain ramp-down of these 3 different types of metals. In my
> non-calibrated ears...... there is a highly measurable differentiable/delineable audio length
> duration between (especially) a diamagnetic vs. ferromagnetic substance/target. I'm uncertain if
> there would be a requirement for an accelerometer. In this case, I speculate not. . . . . . as .....
> simply the 'difference' between the two duty-cycle receive samples, , , , , , , especially with the
> large energy decay ramp-down (or zero hysteresis)....... is a 'tell-all' signature
> emitter........... stand-alone. Diamagnetic materials have virtually no magnetic
> susceptibility/permeability; subsequently, no hysteresis. Ferromagnetic materials are on the
> opposite end of the spectrum....... with maximum magnetic susceptibility/permeability.........
> (posing a large decay ramp-down). Can today's rapid microprocessors 'see' the difference.
>
> ((( Not sure if this is Minelab's MPS Multi Period Sampling ))).

Metal detectors don't work at the level to distinguish diamagnetic and paramagnetic, we just lump it all into "non-ferrous". Without a reactive channel, most PI detectors can't reliably distinguish ferrous from non-ferrous. However, some ferrous targets do give very extended decay responses, probably because their magnetic properties extend the eddy response (my speculation). So, yes, you can add a second late sample and get a better idea of the decay curve. I played around with this several years ago and was disappointed with the results, it was still very unreliable.

Another trick is running 2 or more pulse widths and doing correlation between them to try to ID iron. This is likely what MPS is doing. It probably has similar limitations, and the result is that GPX machines have only rudimentary iron ID. The most reliable method would be to add a reactive channel, but this generally requires using IB coils. I'm currently experimenting with a PI-IB setup for different reasons, and if I continue with it I'll consider adding a reactive channel for iron. It may be possible to add a reactive channel with a mono coil (per claims on Geotech) but I haven't looked into it. Probably it involves closely monitoring the TX transmit current waveform.

At PriorJob I did a lot of exciting work in TD methods, and it was difficult to walk away from all that. I did a pretty good job of wrapping it up in patents, so now I'm trying to figure out how to circumvent my own work and get back to exciting results. It ain't easy, and everyday dept management duties severely eat into my development work.

- Carl

A couple of wise engineers once told me that it is not too difficult for a clever metal detector designer to figure out an exciting new way to do pulse induction - or multi frequency - detecting and get the project halfway. Unfortunately they added that getting it beyond halfway done is incredibly difficult.

Rick Kempf
Gold Canyon AZ- where there is no gold

Geotech Wrote:
-------------------------------------------------------
> It may be possible to add a
> reactive channel with a mono coil (per claims on
> Geotech) but I haven't looked into it. Probably it
> involves closely monitoring the TX transmit
> current waveform.
>
> - Carl

Carl,
Are you referring to moodz latest?
He posted a simple scope trace video that looked very promising...

mike

Yes, I think it was his work. I've only been able to loosely follow Geotech projects lately, so everything's fuzzy.

Thank you, sir. (and can empathize with the 'fuzzy' part)

His latest has been on my radar for a little while now...
We've seen lots of promising stuff just come and go, but this may be legit enough that I might even consider holding my breath for it.

mike

I relic hunt. I started with a xlt. I then moved on to a cz7a pro. Man things really opened up after that for deepest bullet finds. The cz's that I have are bullet machines not all that on buttons though. But I've done very well with them. I got camo F75 I couldn't understand it. So I put it on the back burner but took it along just to mess with relic hunting. I found stuff but not as deep as my cz's. The thing was sparky as it gets. Well I had that machine in a case with my cz3d laying there behind my back seat in my truck. Someone got into my truck & stole it but left my 1021 cz3d laying there. They must have thought it was a cased gun. Oh well I would have cried over it if they had taken my favorite cz. I then got a T2se & put a big sef coil on it. Using that setup I dug a .58" Williams type 2 @ 13". That's the deepest bullet I've ever dug Boy that's a nice setup for minie balls but really sparky I got a g2 & put a ultimate coil on it. The first trip out with that setup I dug a Mississippi A & a block I button. That spot was pounded with whites & my cz's for years. People say that those detectors don't have depth are mistaken. I put after market coils on them & it really put lots of finds in my pockets. The g2, f19 & big after market coils find civil war relics. Depth is everthing. I just got a TDI to try out. We shall see everyone.

Minelabs ahead of that system...

I feel the Garrett ATX is just advancing the pusle delay to full when you use the check button...then using a iron grunt..its not fool proof and it lies to you ..

the Infinium has the iron check feature also activated by full pulse delay it will still tone alert if its iron but if its non ferrous it will go quiet..yet it not perfect...the ATX is a hopped up infinium.the only difference is the infinium does not sound a iron grunt on iron...it still works off the tones...

I feel maybe the ATX is using a full advance delay for the iron check to work...tied to a miroprocessor to turn on a iron report.. yet Ive seen the ATX call stuff iron thats not iron...Like 3 ringers...Infinium the same...

I feel the GPX is using a way more sophisticated way to sample for SOME iron disc..

I may be wrong on the ATX but i dont think so...

Some people do the TDI like that to see if a target is MAYBE iron.. full pulse delay...

Keith

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

Some good info Keith. I can see how the ATX would get fooled on a 3 ringer. And I'll bet it would have a higher tendency to be fooled more by 69s vs 54s. I'll also bet the ATX would be less likely to lie calling a gold ring, gold nugget, and US nickel iron as well. So the break point the ATX senses/uses when using iron check is I feel being challenged with some of the CW bullets. And also some of the alloys used in some of the CW bullets is not spectacularly uniform.



Edited 1 time(s). Last edit at 05/30/2015 12:08PM by tnsharpshooter.

The GPX is a sneaky machine. At first, it is real easy to start trusting the iron "disc" and if it gives a broken tone, then the user assumes its iron and moves on. That's because a lot of times that IS the case for shallower iron, and the deeper bullets/plates will be smooth tones without a broken up signal. In fact I have saw several hunters say if they have a good sounding target and then dig a hole, and the target breaks up when the coil gets closer to the target, that its iron. What I have since found out is that we are leaving a lot of shallower non ferrous targets in the ground by doing it this way. The iron disc and overall gain setting is causing an overload of sorts on shallower strong conductive items. In fact, it has caused me to do a lot of experimenting with settings to find a remedy. Thus far...my remedy is cutting back on the gain by a lot. I'm seeing a lot of guys going all out for depth on these machines. Running high gain and using 12x15 or larger coils. They are making the problem worse. I'm actually running the 5x10 Commander coil the most often now...with my gain setting no higher than 3. I'm finding a lot of larger pieces of lead...minies, etc that are 6 inches or less that will give broken tones when you run high gain or even gain at the factory presets. Its only a matter of time before a plate surfaces due to this.

Mr Dankowski. What can one say other than Thank You. ! You're forum. You're knowledge. You're help and expert advice. Is priceless. It's an honor and privilege. To be a member here. Thank You Sir. HH c t

Carl........ I'm quite glad that you are on (at least) a path of inventive 'chance' with TD/IB PI. If it's one way to skin-a-cat......... the resultant could be revolutionary (vs 'evolutionary' ). As I age................ I realize that I do not detect/hunt for 'hobby' anymore. Rather....... it is more (collective) archaeological & historical (National Society) driven. Many 'eyes' w/noble cause..... driven. I can only hope that Tom affords you the needed allocated resources (money, time, manpower, tools, INSPIRATION) to achieve mini-milestones.
Your incarcerating impositions...... noted/felt.

* On a side note; Aluminum soda tab. Medium conductivity & Low density. /// Gold ring. Medium conductivity & very high density. Electronically differentiable?? ((( Signature-to-hull emitter correlation?!?!! ))) I know I have posted this thought a few times in the past....... up to/including a decade ago; yet, worth the re-mention. On a O-Scope....... if you look at.......aluminum tab vs gold ring........ resistive, reactive, inductive, capacitive (some captured) delta. ((( Voltage vs Current ))).

Gosh.............. If only Alan H. or Kenny W. would 'cut you loose' on your IP........ for the betterment/advancement of mankind. Extenuating variance request.

c t = As you can see/witness.......... it's 'bloodline' !

There has been soooo much 'buzz' lately about unmasking in heavy iron/nails with DD coils and high-frequency detectors..... that has triggered a thought:

* Gold Bug-2 (71-Khz) with a full DD coil (11" x 7") with a 'bp' or 'je' process.

(Yes, , , bird-shot could be a problem).

Explain more, please Tom.
When I read the above, I couldn't work out why you would want such a large coil. Firstly because unmasking rather implies heavy levels of iron, and a large coil would likely be overwhelmed. Secondly, I thought that higher frequency rigs picked up proportionally more ground signal, limiting their depth. So adding a big coil would pick up even more.
I assume you're not actually using the high frequency for finding small objects, you're just wanting good performance in iron. Because small objects (like bird-shot) would probably be harder to find with an 11 x 7 than with a more modest sized coil.

I do think the idea of more coils, and 'more modern' coils for the GB2 would be a good idea. They do still manufacture it, after all. And they could sell them at an appropriate 'premium' price, which might help offset the low-volume manufacturing costs, and R&D costs.

Pimento......... the mindset/thought-process would be for greater depth with the larger coil, better separation with a true DD; yet, such a large coil (although tighter footprint) will sacrifice the separation it gained...... in many cases....... but not all!
A 5" x 9" DD coil (or smaller DD) would sacrifice overall/final depth...... yet, would present even greater adjacent separation abilities........ over current technology (especially to include what is currently offered with a Gold Bug-2).

The Gold Bug-2 is a fairly deep unit on a nickel or a dime; yet, I feel a 11" x 7" coil would bring it to a marked depth gain........ worthy of cause.

When I am performing a Phase-2 Archaeological site recovery with F75LTD in all-metal mode (and in concert with 'bp' mode & 99 Sens)...... there are many (tiny) varying clasps, buckles, clips, pistol percussion caps and many, many other critical implements that are painting a somewhat different historically significant past (potentially re-writing history books)............ that .............. so far.................. only the F75 can find. These tiny implements are (at best) ..... detectable with a CZ to 1". But the F75 will detect them to a nominal average depth of 5". If........ say......... you are using a 1" depth capable CZ (on these tiny implements)........ it takes very little to 'mask' one of these buckles/clasps/clips/Pistol PC cap. With a 5" capable unit........ you have a fighting chance of finding/recovering these significant implements.

A Gold Bug-2 does a wonderful job at finding these targets................ even partially (iron) masked....... due to the nature of it's 71-Khz Op Freq, , , , , yet............... a full DD equipped F75 will still perform better.......... even at it's 13-Khz Op frequency. If only to have a 'boost process' GB-2 with a true 5" x 9" DD coil. ((( Yes: a 'specialty' tool. )))

I was under the impression it was a high-sensitivity machine as standard (I've never used one), so would you be wanting BP mode for searching with the coil clear of the ground (long grass, woodland debris)?
What you're describing is basically an F75 (LTD) running at 50 - 100KHz, which does sound like a good idea. I often wondered why different frequency versions of this platform were never produced. Presumably newer platforms, like the G2 etc incorporate know-how from the T2, so I guess a 70K "G2+" would be the way to go nowadays.

Recently....... I have been detecting a 1875 church site....... and several surrounding acres. In a nutshell........ the 1975 depth strata was located at the 10" - 11" depth mark. How disappointing! Sooooooo........ at what depth strata is the 1875 implements?!?!? This is an exceptionally common occurrence in this 'sand bar' Florida soil. I simply wish for a paradigm shift away from electromagnetics to a different medium of detection. Yes....... this is not the first time for this thought/request. I know I have been bringing this up for decades. If I had the time/resources ........... I would vest 'all' into this quest................ as the 'cause' is highly valued.

How soft (mechanically speaking) is this sandy soil? Could a probe, say 3 - 4mm (1/8th inch) be inserted to any significant depth? I'm thinking of the Ott "Periscope Probe", or some similar tool. As your 'dirt' gives a weak signal to a detector, that opens up the possibility of greater performance from the tiny search-head.
I did tinker around with a homebrew version of this probe. Based around a BFO circuit, so it would give some discrimination. It did actually work, with a tiny commercial axial inductor. One tricky step would be encasing the probe, it would have to be inside a tough ceramic sleeve (I think the Ott probe was done this way) as it's on the business end of a spike.

It would be fairly easy to push a 1/8" (even a 1/4") diameter probe to depths of 4-feet (Only roots would/could inhibit). This sure would be a very slow/inefficient process; yet, does provide an (laborious) option.

The 1975 implements you found at 10+" had an average sink rate of a 1/4"+- per year (doesn't sound like much but it's a heck of a lot). . . . . Jeez, 1875 stuff could be at 3 feet +- deep. That probe would be interesting, Pimento....like to see one in action.

That soft ground sounds ideal for such a probe. As for the laborious nature of it, I agree, I was thinking of the scientific research aspect, where if it even gave one valid result it would have merit.
I've not thought too hard about the practicalities of making the probe, but I know there are several patents related to the Ott probe which are easily found. One interesting feature it has is that it 'looks' sideways. This is achieved by cutting the ends of the ferrite probe at 45 degrees, so the magnetic field is biased one way. That feature wouldn't be needed for Tom's situation, I think.
Here's the original Ott Periscope Probe patent:
[www.geotech1.com]
His probe is described in the patent as a 0.226" (5.7mm) diameter stainless steel tube, with a Zirconia tip containing the coil. The length was 14" overall.

On this topic - I'm not a bottle-digger, but those guys use mechanical probes to find buried glass. Typically 2mm spring-steel, long length, with a T-handle joined on the end. Inserted into the ground, they can be heard to give a distinctive 'glassy thunk' when a bottle is 'hit'. I wonder if this technique would find targets in Tom's soft sand?
Probes can be home-built easily, metal suppliers usually stock the spring-steel wire.



Edited 1 time(s). Last edit at 08/27/2015 12:40PM by Pimento.

I speculate the targets that I am looking for........ are in the 27" - 31" depth strata. I may have the opportunity to perform a unique test in the near future. Will post results..... should fruition ensue.

NASA-Tom Wrote:
-------------------------------------------------------
> I speculate the targets that I am looking
> for........ are in the 27" - 31" depth strata. I
> may have the opportunity to perform a unique test
> in the near future. Will post results..... should
> fruition ensue.

I know on Hilton Head Island in Archaeological test pits back in the 90's I saw 3 ringers at 5 feet deep....

yet I dug three ringers at a foot or less also????

Weird..

Keith

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

Keith,

There's always a certain percentage (usually a very small percentage number) of targets that do not sink deep. . . . . hence, within detectable range.