dumb question? today's detectors can ID by conductivity and iron content, why not density?

and would that be a good thing?

[www.engineeringtoolbox.com]

Wayne

To measure "density", would require you to take the object and measure it's dimensions, then weigh it, in order to get its density. If you have the object out of the ground to do all that, then you can merely look at it, so see what the object is (gold vs. aluminum). Eh ?

If someone ever figures out a way to remotely measure the density of objects using an electromagnetic field they will win a Nobel prize and acquire riches beyond the dreams of avarice.
I am currently working on it in my shed and expect to solve it in a few thousand years or so...

There already is a way to measure density its called x-rays.

You could measure density using simultaneous multi-frequency VLF where you measure and report responses from across a broad band of frequencies starting very low and moving higher to some mid range cut off. Say 1 to 30 kHz. It is easy for a high frequency to create skin effect eddy currents, but it much harder for the lower frequencies to create a skin effect eddy current. The more dense the item, the more ability of the item to hold onto the lower frequency eddy current effect.

You can see this with a Whites V3 and light foils. The higher 22.5 frequency will report hard on it but often times the lower 2.5 frequency will not report on it at all, or very irregularly if it does report. So the ability is there, just not refined yet.


HH
Mike

A small silver/gold hammered coin can hit just like aluminium foil but obviously their densities are very different, could the analysis of eddy currents differentiate?


A detector that could actually remotely detect the density of objects could be set to ignore all other objects with a density less than lets say 14ct gold, a person could then swing that detector in the happy knowledge that it would never beep on any other object with a density less than 14 ct gold as almost nothing else in the ground including lead has a higher density.This would be metal detecting Nirvana but I don't think we'll see it in our lifetime...if ever.

I'm sure there was a time when some thought that a measurement of conductivity would require the same approach.

Wayne

Beyonder-Pa Wrote:
-------------------------------------------------------
> There already is a way to measure density its call
> ed x-rays.

And x-rays require there to be a receiving field at the other side of the object. Like medical x-rays, the patient stands between the 2 parts of the x-ray unit. Hence non-applicable to us. Unless, of course, you dig out from under the object, put the receiving side, and then do the x-ray, haha. But by then you could have dug up the item and simply looked at it.

ncwayne Wrote:
-------------------------------------------------------
> I'm sure there was a time when some thought that a
> measurement of conductivity would require the same
> approach.
>
> Wayne

Wayne, this catchy way of looking at hoped for technology, would only apply if the task-in-question were physically possible. If a task is impossible, then no amount of looking back at past inventions "that came true", will change the laws of physics going forward.


Not saying that there isn't a possible way in the future to tell gold from aluminum . Ie.: measure density vs conductivity and compare for purposes of passing aluminum. But just saying, that just because something got invented in the past, does not, therefore, make any possible notion , going forward, of necessity "possible" . There will be some things that are impossible and bound by the laws of physics.

uh, Tom, I hate to break it to you but the "laws of physics" have been broken many times in the past, and as long as folks are still engaged in the study of physics, there is every likelihood that they will be broken again in the future.
Broken, here, means changed to reflect new learnings.

EDIT: I have to add that I don't believe the possibility of remote measurement of density is a matter of physical laws, but has more to do with the application of those laws. And measurement does not have to be finite. It can simply be comparative.

I am not saying density determination is possible, but unlike you, I am not saying it is impossible, either.
I asked the question because I don't know.
No "catchy" intended <g>.

Wayne



Edited 1 time(s). Last edit at 03/15/2018 03:49PM by ncwayne.

ncwayne Wrote:
-------------------------------------------------------
> uh, Tom, I hate to break it to you but the "laws o
> f physics" have been broken many times in the past
> , and as long as folks are still engaged in the st
> udy of physics, there is every likelihood that the
> y will be broken again in the future.
> Broken, here, means changed to reflect new learnin
> gs.
>
> I am not saying density determination is possible,
> but unlike you, I am not saying it is impossible,
> either.
> I asked the question because I don't know.
> No "catchy" intended <g>.
>
> Wayne

Wayne, good conversation/topic.

If you say "the law of physics were broken in the past", then we have a definition problem here. Because, then, by definition, they were NOT the laws of physics. Ie.:someone only SAID 'such & such is impossible', and was simply wrong.

Eg.: heavier than air flight, earth is flat, etc... are all examples of what science once held to. Right ? But those are all merely examples of where science held erroneous beliefs. Not that "anything is therefore possible going forward".

And I, like you, am not saying the present topic is "impossible", I'm just saying that not all fancied inventions are, of necessity, possible. Simply because of past inventions. The fact that something "got invented", means it WAS possible. Not that "all things are possible".

There is a lot of room to move the V3i forward. I keep hoping Whites will do it. But the hope is low as I see most folks don't want to program their own units.

HH
Mike

What about ground penetrating radar? Or the new detector Nokta was showing that has a color screen that differentiates target ID and shape? I know there have been others previously.
I know that is not exactly what was asked for, but do they not show potential?

Past(or)Tom
Using a Legend, a Deus 2, an Equinox 800, a Tarsacci MDT 8000, & a few others...
with my beloved, fading Corgi, Sadie



Edited 1 time(s). Last edit at 03/15/2018 04:37PM by Pasttom.

Pasttom Wrote:
-------------------------------------------------------
> What about ground penetrating radar?


That's only for shape. ( and terrible pixel sizes at that). Nothing to do with composition or density.

Mike Hillis Wrote:
-------------------------------------------------------
> There is a lot of room to move the V3i forward. I
> keep hoping Whites will do it. But the hope is l
> ow as I see most folks don't want to program their
> own units.
>
> HH
> Mike


Mike, this is the age-old fancied musings. When the very first TID detectors hit the market (teknetics), we were all giddy thinking we could pass aluminum in favor of gold. But of course, that's only an ascending and descending conductive scale. So not of much use except for notching. Then fast forward to the spectrum and XLT. They had much more information. But alas, still useless for the purposes we're discussing. And then machines like the Explorer, with the up down, left right Axis. And the machines like the v3i. But as they are, no amount of studying the cursor or fiddling with the controls will solve the aluminum versus gold issue.

The Rutus Alter71 appears to be the first detector to give you a wide range of frequencies to chose from, albeit one a time. But even that could work if you could pinpoint the object and then push a button to hit it with a lower frequency and check the response. Even a response as simple as signal strength could tell you something additional about the target.

Back to the V3, because the V3 shows you the response in three different frequencies. The spectragraph is showing you VDI numbers and signal strength of the target at all three frequencies. Those lighter, low conductive targets light up hard and sharp in 22.5, but soft and fuzzy in 2.5. That capability needs to be improved upon and enhanced.

I have ideas, man, I have ideas! HA!

HH
Mike

Tom_in_CA doesn't the GPR indicate density by the opacity of the image? I had just assumed this to be the case and I know the risk of such thinking... The tech seems to me to be somewhat like VLF on steroids with very heavy power requirements.

Past(or)Tom
Using a Legend, a Deus 2, an Equinox 800, a Tarsacci MDT 8000, & a few others...
with my beloved, fading Corgi, Sadie

Forget density....I am working on a new unit that will be able to measure the chemical composition of an object and determine via the number molecules and atoms whether an object is iron, aluminum, silver or gold.

It will be offered in 2 models at a very low cost. Beginner model at $299. Advanced model at $399.

Only one caveat....they both weigh 15 tons. But I may offer a 'light weight' model with super cool wireless headphones at 13.5 tons.

therover61 Wrote:
-------------------------------------------------------
> Forget density....I am working on a new unit that
> will be able to measure the chemical composition o
> f an object and determine via the number molecules
> and atoms whether an object is iron, aluminum, sil
> ver or gold.
>
> It will be offered in 2 models at a very low cost.
> Beginner model at $299. Advanced model at $399.
>
> Only one caveat....they both weigh 15 tons. But I
> may offer a 'light weight' model with super cool w
> ireless headphones at 13.5 tons.

Ok. And you'd have to wear a lead suit to protect yourself, and the device is mounted on a bobcat tractor, eh ? This was actually invented by Westinghouse in the late 1980s or early 1990s-ish. For a govt. contract to detect compounds (explosives, contaminents, etc....). I talked personally to the top engineer (as he was a co-worker of my father in laws). I explained the dilemma that md'rs face (foil and tabs vs gold rings). And explained out a TID signature could be identical between the same, even though 1 is aluminum and the other is gold. He listened carefully and said that .... yes .... their device could tell the difference in composition.

But as said, you'd have to wear lead suits, get reams of govt. clearances and licenses to operate, is mounted on a bobcat tractor, and cost millions.

The Equinox 1000 will be able to tell foil from rings using a Hodograph type display. Yeah I wish. LOL

____________________________________________________________________________________________________________
In a democracy, it is difficult to win fellow citizens over to your own side, or to build public support to remedy injustices that remain all too real when you fundamentally misunderstand how they see the world.

Tom_in_CA Wrote:
-------------------------------------------------------
> therover61 Wrote:
> --------------------------------------------------
> -----
> > Forget density....I am working on a new unit tha
> t
> > will be able to measure the chemical composition
> o
> > f an object and determine via the number molecul
> es
> > and atoms whether an object is iron, aluminum, s
> il
> > ver or gold.
> >
> > It will be offered in 2 models at a very low cos
> t.
> > Beginner model at $299. Advanced model at $399.
> >
> > Only one caveat....they both weigh 15 tons. B
> ut I
> > may offer a 'light weight' model with super cool
> w
> > ireless headphones at 13.5 tons.
>
> Ok. And you'd have to wear a lead suit to protect
> yourself, and the device is mounted on a bobcat tr
> actor, eh ? This was actually invented by Westin
> ghouse in the late 1980s or early 1990s-ish. For
> a govt. contract to detect compounds (explosives,
> contaminents, etc....). I talked personally to th
> e top engineer (as he was a co-worker of my father
> in laws). I explained the dilemma that md'rs face
> (foil and tabs vs gold rings). And explained out
> a TID signature could be identical between the sam
> e, even though 1 is aluminum and the other is gold
> . He listened carefully and said that .... yes .
> ... their device could tell the difference in comp
> osition.
>
> But as said, you'd have to wear lead suits, get re
> ams of govt. clearances and licenses to operate, i
> s mounted on a bobcat tractor, and cost millions.

Dang it Tom....why did you spoil all my fun. Good thing I was just in the infancy phase of the project !

Tom_in_CA Wrote:
-------------------------------------------------------
>The fact that something
>"got invented", means it WAS possible.
>Not that "all things are possible".

Well speaking of inventions,,,,,, how about my modified CZ ?



Up to my ____ in Pulltabs, Grant

pretty funny U.T.M._I.P.T. ><

I know that I've mentioned this multiple times....... and over the course of a dozen years; yet, worth repeating.

There is indeed a signature-to-hull-emitter-correlation between (say) a mans gold ring..... vs..... a aluminum soda pull-tab. The gold ring is high-density. The aluminum tab is medium-density. This can be witnessed on a O-Scope...... with enough delta to differentiate. Although both items are 'conductively' the same.,.,.,.,.,.,., "conductive analysis" is NOT the answer. There is another unit-of-measurement methodology (2nd Generation) that we have not incorporated (yet). In various engineering departments......... the thought of "it can't be done"......... sure is crippling (and old-school).

The only folks likely to know of a method for doing this in a reasonably priced hobbiest metal detector are likely engineers at metal detector companies. Any ideas which they have on how to do this are unlikely to be disclosed in a public forum.

Rick Kempf
Gold Canyon AZ- where there is no gold



Edited 1 time(s). Last edit at 03/16/2018 02:09PM by lytle78.

NASA-Tom Wrote:
-------------------------------------------------------
> I know that I've mentioned this multiple times....
> ... and over the course of a dozen years; yet, wor
> th repeating.
>
> There is indeed a signature-to-hull-emitter-correl
> ation between (say) a mans gold ring..... vs.....
> a aluminum soda pull-tab. The gold ring is high-de
> nsity. The aluminum tab is medium-density. This ca
> n be witnessed on a O-Scope...... with enough delt
> a to differentiate. Although both items are 'condu
> ctively' the same.,.,.,.,.,.,., "conductive analys
> is" is NOT the answer. There is another unit-of-me
> asurement methodology (2nd Generation) that we hav
> e not incorporated (yet). In various engineering
> departments......... the thought of "it can't be d
> one"......... sure is crippling (and old-school).


I remember reading a story about a guy that was using an o-scope to show the difference between tabs and rings and, from what I remember, it worked flawlessly..

It can be done, and here's how you do it. Oh wait, Rick's right, can't divulge that just yet. But if it works, it'll make all other detectors obsolete.

NASA-Tom, Geotech, and Beyonder...

I asked this question 6 or 7 years ago here on the forum, and I can't recall the responses, but nothing really stands out in my mind that was said in the responses back then that made me think such a technology was "imminent."

From your answers, however, it sounds like not only is it technologically within reach, there's an avenue there to be exploited should some "inside-the-box" type of "road blocks" be removed. Yes, Geotech, I would think that indeed, such technology -- if incorporated into hobby detectors -- would indeed "obsolete" some machines...

Steve

NASA-Tom Wrote:
-------------------------------------------------------
> This ca
> n be witnessed on a O-Scope...... with enough delt
> a to differentiate. ...

I bet that the items that can be "differentiated", will be 2 given sample test objects. Eg.: a certain select pulltab and a certain select gold ring. Which, yes. .... will admittedly have an identical TID on a detector. But as you say, there WILL be a "difference" when those 2 items are tested on an O-scope. Right ? Ok, but here's where the devil is in the details: I'll bet I can come up with an aluminum object (given enough folding over of a random piece of aluminum, or packing a ball-wad tight enough) that I can EXACTLY MIMIC the O-scope reading you're getting off the ring

There is lots to be “figured out” - invented - and developed yet. Massive parallel processing - using graphics chips to run deep learning algorithms.

Only one problem. That kind of work costs millions of $$ Per month (or even Per week) - and teams of extremely scarce superstar engineers.

Our suppliers - even the best of them don’t have those kind of resources.

Fortunately - some real progress can probably be made by the folks hard at work in a few metal detector companies. It is clear that some talented folks are in fact employed in the industry that gives us our tools.

How about we all cross our fingers - and meditate on the Wevster’s dictionary definition of patience.

Rick Kempf
Gold Canyon AZ- where there is no gold