link
I don’t post videos here anymore. I’ll send you link via pm. Least I can do.
link
Again, I know the ID can change with different weights.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.
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.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.
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.I tested more than 1 aluminum cap.
I'll be comparing M2 which is weighted at around 40khz, to both M1 (15khz), and M3 (7khz).Legend use- you would want to compare using the new whatever that was incorporated with update. (Lower freq).
Will do.For gee whiz. On air test - look at 5 kHz too.
Well stated and summerized AC, and now I realize I don't know crap compared to well seasoned members such as yourself.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.
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".