Minelab Manticore Aluminum Bottle Screw Cap Rejection

[tnsharpshooter]

link

I don’t post videos here anymore. I’ll send you link via pm. Least I can do.

 

[Diga]

I watched your video TNS.

Thanks for mentioning my name in the video. Thing is, I never denied the ID can, and often does, change with different frequencies, nor do I have to own a D2 to know that...so I don't know what the heck you're blabbing on about that for.

I just popped in to say that, but I have some comments about the video that I'll post later when I have more time.

 

[tnsharpshooter]

The ID changes. But what is the tendency of the ID (per freq) used vs what’s under the coil. That’s the key. And program deep high conductor is using some real low freq vs most other SMF detector setups.

 

[tnsharpshooter]

Also check out a final GEN IH coin and compare. There is a difference . 14khz max will read higher vs 40 kHz max program.

 

[Diga]

The ID changes. But what is the tendency of the ID (per freq) used vs what’s under the coil. That’s the key. And program deep high conductor is using some real low freq vs most other SMF detector setups.

Again, I know the ID can change with different weights.

I still want to have a deeper look at the video, and will do so later tonight. In the meantime, did you test the method with a copper and zinc? Also, did you test angled and edged coins, and various caps?

 

[tnsharpshooter]

Copper and zinc is in video. I do look at final gen IH coin. It behaves like zincoln and copper penny. Not like the aluminum twist cap.

Basically what I do is dig all ties and ones reading higher when checking with 14 khz max freq. when I refer to the “dig all ties” I am referring only to the 82-87 range signals acquired using 40 kHz max freq program while detecting.
Now if I got a weak(.er) signal I could still dig. Thinking deeper. I did however see the behavior shown in video on some
7-8 “ deep aluminum twist caps.
But strong (er) would suggest not deep. And ID definitely odds wise more trustworthy.

Disclaimer.
All my use testing while in the wild has been on medium and milder soil.
NOT super high mineralized soil. So for this kind of soil. I can’t say what will happen.

 

[Diga]

Disclaimer.
All my use testing while in the wild has been on medium and milder soil.
NOT super high mineralized soil. So for this kind of soil. I can’t say what will happen.

I've got mild soil, so an air test will suffice. On my day off (Sunday), I'm going to do similar testing with my Legend, but I will test using more than one noncrushed aluminum cap, as well as coins that aren't lying flat. For the latter, it's because I'm assuming that most coins in the ground aren't lying flat.

Hopefully, some others can do a similar test with whatever SMF detector they're using.

 

[tnsharpshooter]

I tested more than 1 aluminum cap. This why why I started using it in the wild. I also verified several located in the wild caps too. Both uncrushed and crushed. Crushed ones will not usually give ID difference.
I don’t just see a one off and run with it.
Not my style.

NOw Mr T’s Gold Ring. That’s where one could get fooled.

I should also point out.
Users of Deus 2. If one decides to cherry pick. Good ides to know Deus 2 ID tendencies per freq channel used. ID of targets can change as as freq is raised and lowered via freq channel selection used.

 

[Diga]

I tested more than 1 aluminum cap.

It's not so much the variations in the caps that I'm concerned about. Rather, I'm more concerned about what will be the ID change (if any) on lower signal strength edged coins, because I suspect most coins in the ground aren't lying flat. I'm going to test a silver ring and a large diameter gold band ring as well.

 

[tnsharpshooter]

Done tested large diameter 14 k band. It behaves more like twist cap. Meaning higher reading acquired using 40 kHz max freq vs 14 kHz max freq. Think I saw though 5 points of ID difference.

Legend use- you would want to compare using the new whatever that was incorporated with update. (Lower freq).

 

[tnsharpshooter]

As far as Manticore goes. I’ll look at it tomorrow. Again.

 

[Diga]

Legend use- you would want to compare using the new whatever that was incorporated with update. (Lower freq).

I'll be comparing M2 which is weighted at around 40khz, to both M1 (15khz), and M3 (7khz).

 

[tnsharpshooter]

For gee whiz. On air test - look at 5 kHz too.

 

[Diga]

For gee whiz. On air test - look at 5 kHz too.

Will do.

Although I don't hunt in SF, because I find target identification to be significantly more accurate using SMF.

 

[AccurateCalls]

Uncrushed aluminum screw caps tend to produce wider / more oblong renderings on the 2D screen typically without any verticality... but so can some desirable targets, e.g. an old corroded copper coin. Any time you try to reject a bad target, you will inevitably lose a good target. Sometimes hunting conditions can make this tradeoff worth while, other times not.

It should be noted that aluminum is paramagnetic, which means it internal magnetic domains weakly align in the direction of the transmitted field. This magnetic response (positive inductive reactance) competes with the diamagnetic-like eddy current response (negative inductive reactance) and the ratio of these responses in combination with resistive heat loss determine the phase angle response (and thus TID) and is mildly dependent upon the transmitted frequency, e.g. higher frequencies don't penetrate as deep and thus produce weaker magnetic domain alignment or a weaker magnetic component, where as any given material has an 'optimal' frequency that maximizes penetration and absorption of the transmitted field. This is why TID can change when you change frequency or SMF frequency weighting.

Aluminum's weak magnetic effect from internal domain alignment is outcompeted by the conductive properties of aluminum which produces a strong eddy current diamagnetic-like response (since eddy currents generate a secondary magnetic field that opposes the direction of the primary magnetic field) thus a detectors perceives the paramagnetic material as being non-ferrous. Also the somewhat high resistance of aluminum causes these eddy currents to dissipate faster in the form of heat, which leads to smaller inductive reactance responses, and thus typically smaller phase angles (lower TIDs). Since these eddy currents rapidly dissipate in the form of heat, the aluminum object's ability to store opposing magnetic field dissipates quickly (short time constant).

Other objects, with differences in inherent magnetic permeability, resistance, topology, etc., each have an optimal frequency(ies) that 'maximizes' a target's phase angle response (or the ability to store magnetic field) and this complex relationship applies to all possible materials. This is precisely the reason why SMF detectors produces better TIDs because they are comparing how this relationship changes over a variety of frequencies.

My point is, the physics at play in relation to frequency is rather complicated and highly variable depending on the object so any of these "change the frequency and see how the TID changes"-type-strategies is going to be subject to so much complexity that any patterns that emerge are likely imagined and are the result of the particular bin of sample objects being used and not statistically significant in the long run. If all it took to identify aluminum from other objects was to look at how the TID changes across different frequencies, this feature would be coded automatically into an SMF machine and they would have an aluminum-check feature (like ferrocheck, but instead gives a readout of the probability of the detection being aluminum).

I don't really buy into any of these "identify aluminum with this one simple trick!" type stuff. The set of all possible targets out in the wild is too vast.

 

[markinmichigan]

Uncrushed aluminum screw caps tend to produce wider / more oblong renderings on the 2D screen typically without any verticality... but so can some desirable targets, e.g. an old corroded copper coin. Any time you try to reject a bad target, you will inevitably lose a good target. Sometimes hunting conditions can make this tradeoff worth while, other times not.

It should be noted that aluminum is paramagnetic, which means it internal magnetic domains weakly align in the direction of the transmitted field. This magnetic response (positive inductive reactance) competes with the diamagnetic-like eddy current response (negative inductive reactance) and the ratio of these responses in combination with resistive heat loss determine the phase angle response (and thus TID) and is mildly dependent upon the transmitted frequency, e.g. higher frequencies don't penetrate as deep and thus produce weaker magnetic domain alignment or a weaker magnetic component, where as any given material has an 'optimal' frequency that maximizes penetration and absorption of the transmitted field. This is why TID can change when you change frequency or SMF frequency weighting.

Aluminum's weak magnetic effect from internal domain alignment is outcompeted by the conductive properties of aluminum which produces a strong eddy current diamagnetic-like response (since eddy currents generate a secondary magnetic field that opposes the direction of the primary magnetic field) thus a detectors perceives the paramagnetic material as being non-ferrous. Also the somewhat high resistance of aluminum causes these eddy currents to dissipate faster in the form of heat, which leads to smaller inductive reactance responses, and thus typically smaller phase angles (lower TIDs). Since these eddy currents rapidly dissipate in the form of heat, the aluminum object's ability to store opposing magnetic field dissipates quickly (short time constant).

Other objects, with differences in inherent magnetic permeability, resistance, topology, etc., each have an optimal frequency(ies) that 'maximizes' a target's phase angle response (or the ability to store magnetic field) and this complex relationship applies to all possible materials. This is precisely the reason why SMF detectors produces better TIDs because they are comparing how this relationship changes over a variety of frequencies.

My point is, the physics at play in relation to frequency is rather complicated and highly variable depending on the object so any of these "change the frequency and see how the TID changes"-type-strategies is going to be subject to so much complexity that any patterns that emerge are likely imagined and are the result of the particular bin of sample objects being used and not statistically significant in the long run. If all it took to identify aluminum from other objects was to look at how the TID changes across different frequencies, this feature would be coded automatically into an SMF machine and they would have an aluminum-check feature (like ferrocheck, but instead gives a readout of the probability of the detection being aluminum).

I don't really buy into any of these "identify aluminum with this one simple trick!" type stuff. The set of all possible targets out in the wild is too vast.

Well stated and summerized AC, and now I realize I don't know crap compared to well seasoned members such as yourself.

Mark in Michigan

 

[tnsharpshooter]

Detector manufacturers put meters on detectors don’t they?
Why?
Is the meter accurate 100 percent of the time ?
Nope
So everyone should put tape over their meters then. Right?
Is the audio supposed accurate (correspond) to target’s conductivity (airtest) when buried ? Nope,
So everyone should be running 2 tone then right?

Yeah.
Dig all is not practical all the time for a detectorist.
Could be based on site, targets of interest, weather, ground conditions, or time one has to detect, or even the their physical health.

Every time it seems the critics want to come out and shoot things down.

The Minelab FBS/FBS 2 detectors sure did find a shxt load of coppers and silvers in USA over the years.
Why? Hmmm

Yeah I know why. One big reason is folks weren’t wasting their time digging bs. Instead digging the loot.

I have been up front that no system is full proof. Yet the system can help folks.
I am a practical person.
And share info.

 

[Diga]

If someone figured out a way to avoid those caps for the high conductor cherry picker, then it would be headline news in the metal detecting community. Too bad that headline doesn't exist.

If all it took to identify aluminum from other objects was to look at how the TID changes across different frequencies, this feature would be coded automatically into an SMF machine and they would have an aluminum-check feature (like ferrocheck, but instead gives a readout of the probability of the detection being aluminum).

Your quote is similar to my above quote.

With the method in question, under very particular conditions, with a very specific type of aluminum cap, the method may seem to work in a particular control test. My concern, as I previously mentioned, would be the amount of false positives that would result in many good targets being missed. Enough so, that the outcome will likely result in more missed good targets, than more missed caps. Which is also why, I labeled the very slight change in ID as "precarious" and "splitting hairs".

 

[stetam]

I'm glad I don't use those machines. Waaaay to much work.

Steve

 

[AccurateCalls]

Your quote is similar to my above quote.

With the method in question, under very particular conditions, with a very specific type of aluminum cap, the method may seem to work in a particular control test. My concern, as I previously mentioned, would be the amount of false positives that would result in many good targets being missed. Enough so, that the outcome will likely result in more missed good targets, than more missed caps. Which is also why, I labeled the very slight change in ID as "precarious" and "splitting hairs".

People also don't realize the importance of sample size when it comes to evaluating whether one of these strategies works and produces real world results. Far too often they dig 10 or 20 targets in the same location and that is "all the proof they need" to know that their technique works. We humans are very prone to seeing patterns where there are none.

If given a fair coin, and you try to guess the outcome of a flip, the expected value would be 50% correct guesses and 50% wrong guess. But in a set of only 20 flips, you might have a series where you just so happen to get 70% correct, which would seem to suggest you are great at predicting the outcome of coin flips, or that you have some special technique or method to predict coin flips, but such is not the case, and this is just because a small sample size can be subject to a high degree of statistical variance.

Same goes for when people field test these strategies. It may be the case that they dig 20 targets and their technique appears to work 70% of the time, and thus they are convinced it is doing something, but that sort of outcome is also possible if you were just randomly guessing.

So unless somebody produces an actual data set of their method being field tested across hundreds, if not thousands of targets (and let's be honest, they never do, they never record data, they ALWAYS go by feeling of whether the first 10 or 20 times appears to be working), then I wouldn't take them seriously. Not once have I ever seen a data set proposed alongside one of these techniques which are also claimed to have been 'proven in the field', but they really haven't been proven because they aren't going by actual data and statistical analysis, they are going by 'gut feeling' based on early outcomes from a limited data set. Same goes for when other people try their technique.