detector design thought/question (regarding gold detection)...

I was thinking...(no wise cracks, please! ) With the majority of gold reading right in the same range as the majority of the non-ferrous junk -- i.e. in the foil to pulltab range...it seems clear that if any detector manufacturer could offer EVEN A LITTLE better ability to sort the gold items from the foil and pull tabs, that'd really be a breakthrough. Duh! Nothing earth-shattering there. But, my question is, though I'm sure it's been thought of before -- why can't the DENSITY of the target somehow be measured, even if IMPERFECTLY. I mean, consider the density/weight of a gold piece, versus a similarly-sized piece of foil or a pull tab. Almost all the trash that rings up in the range where most gold reads has MUCH MUCH less mass than gold. TREMENDOUS difference there. Is there not some way to add an additional "process" of some sort, that would attempt to gauge the mass of the object, relative to its size? Any ability to add such a process -- again, even if highly imperfect/imprecise -- to existing target identification/discrimination software in the machine would potentially be a HUGE advance -- a tremendous benefit for detectorists, and of course, a HUGE edge over the competition for whichever company could incorporate such a thing, if even possible. I can't imagine that there's not SOME way to move in that direction...

NASA Tom, is there not some unique way transmitted electromagnetic radiation is affected by an object with very high density/mass, versus how that radiation is affected by a similar-sized object with very low density/mass?

Steve



Edited 3 time(s). Last edit at 06/26/2011 02:41AM by steveg.

I am interested too. Also, why isn't anyone working on improved ground penetrating radar that goes beyond producing a graph and then having to interpret the graph produced by the laptop computer. Where one can actually see shape of object. Might have to be a 2 piece set-up (detector+computer) like it is now. Although I think it can be considerably smaller in size than todays units. Current low power computer processors should have enough oomph to translate graph based signals received into graphic images.

A coincidence to see this comment here.

I'm swinging an XP Deus at the beach... and today I was especially struck by how I can always tell a nickle from a pulltab even though both have similar VDI's. The only thing that would explain it is the density difference. I've also noticed that I am getting much better at recognizing foil signals. They are sharp but "tinny" and scratchy sounding. Coins have a steady sweet sound.

What I'm planning to do is to take a half dozen gold rings and an equal number of pulltabs and nickles and scatter them in a controlled beach area. Then put this theory to the proof.

The 4th of July holiday is the best day on the beach for me and I need to get this done before that. Practice makes perfect.

Regards, Joe

AU21-X ; )

Don't we all wish for something like this.
The simple answer is metal detectors are doing good if they can give us a ferrous/ non-ferrous difference.
They do have problems even in this regard to some degree.

That middle range is filled with all types of objects, mostly junk and trash.
Even shooting for the nickel range, one usually will dig more trash than nickels.
I think detector technology is about as good as it will get, using the current VLF method.
Though I hope I am totally wrong about that.

Then if you add soil matrix, deeper buried objects and objects on edge, then it starts to get
even more dicey for a good ID.
I have the feeling that if they could devise a system to measure density, they would have already
let all of us know.

You would think there is a different return signal for a solid gold ring compared to foil or a pulltab
maybe it can't be measured with a visual reading?
On the other hand a metal detector is just that...something that likes all types and kinds of metals.
It doesn't matter to the detector what the metal is...iron, aluminum, gold, copper, silver, zinc, etc.
Manufacturers have provided aids in trying to sort out conductivity, strength of signal and to some
extent size.

BTW, over on Geo a few years back a guy was using a computer to analyze the signal with but
I haven't followed that lately.

Maybe we need to hear from the ones who are using the DFX or V3, I hear those 2 detectors
have the ability to expand the midrange....maybe that would give an advantage?

If someone would produce a detector that could tell the difference between gold and aluminum
in the first 3 inches of depth, I would buy it tomorrow, though I don't think this will ever happen.

Steve wrote: "Maybe we need to hear from the ones who are using the DFX or V3, I hear those 2 detectors
have the ability to expand the midrange....maybe that would give an advantage?"

I do not know about the DFX, however I can speak for the V3 that yes, it does have the ability to expand the midrange. However, it also has the ability to expand the low & high range as well. The V3's VDI gold scale looks like this:

0-14 Foil and Gold Chains & Thin Ladies Gold Rings
15-25 Foil, Pulltabs and Thin to Small Mens & Womans Gold Rings
25-50 Pulltabs and Small to Large Mens and Womans Gold Rings

All the gold jewelry Ive found so far with the V3 was within the 15-25 range (pulltabs, beaver tails and slaw). I did however recover a mens large diamond 10k gold ring for someone a couple weeks ago that came up 47 on the VDI.

On the DFX changing freq to 3 or 15 would affect the gap.... but each of these freqs have a down side... either mineral or EMI. I think GB also affects our ability to find these objects because of the salt setting.

Dew

Any way of cutting down the odds junk versus gold rings would be a plus.and what you call mass or density I call weight as a gold ring usually weighs much more than the trash that mimics them and of course their are exceptions such as keys, fishing weights which are also heavy.Best I have ever seen along this line are 20 year old Tesoro's that just hold a tone longer on heavier objects and cut down the odds and have been laughed off forums when I brought the subject up as most said a gold ring and junk just sound the same. Glad a light is going on in some other guys heads. Would it be a good thing is another question if a manufacturer came out that could really cut down the odds as certainly most parks would have very little picking relative gold rings as most would be had so guess there are pro's and cons.
Lets face it technolgy is getting better every day and perhaps one of these days we will see a unit to cut down the odds considerbally using the weight theory but we will never see a unit to tell absolutely and even 50 percent would be a major breakthrough. Right now only way I can is to dig all and of course using an old Tesoro I can cut down the odds to a degree. Seems like the deus is on the right track and only time will tell. Old timers used audio variances but it seems they have gone away cluttered by bells and whistles and certainly look forward to any improvements even if they just cut down the odds..I am sure we all have our little ways with gold rings sounding more mellow, hitting harder etc. but an actual proof positive addition to modern metal detectors would be welcomed and still not sure if it would be good or bad for the hobby as most parks and the liked would be cleaned out of gold rings but always plus and minus in all aspects of the hobby..

Sounds like some folks have been reviewing details of one of my seminar presentations on this topic that I gave 7 years ago.

NASA Tom...

I'm not familiar with your reference to a "seminar presentation." Was it in relation to this "density/mass" thought I brought up? If so, I'd LOVE to have more information on what you presented. Like I said, I am sure this idea is not "new;" just curious as to why it, so far, it apparently cannot be done (at least in non cost-prohibitive way). Obviously, ID/discrimination ability of a detector is relatively inaccurate, and likewise I don't expect anything to say "this item is GOLD." But, something that could say "hey, while this is a 'pull tab-type' VDI, this target seems to have more substantial mass to it," that would be GREAT. I am sure that such an attempt to gauge "mass" would not be anywhere NEAR foolproof. But, even something that helped to "up the odds," JUST A LITTLE, of discriminating WHICH foil or pull-tab VDIs are more likely to be just that (junk), and which ones may be something with more mass, would certainly be helpful.

Steve

Steve,

If...........by remote chance...........you can make it to Florida; yes, I would give one-on-one training on this exact topic......and with a fairly good (real world unit) solution.

NASA Tom --

Really? I am most intrigued...

We vacationed with our daughter in Florida about a year and a half ago; I am sure we will be returning in the future though not sure when. Maybe in a year or two. I will be certain to take you up on your offer, when we do -- if not before (I had planned to ask you for an appointment for some training anyway, the next time I am in that direction; this make it doubly important to me...)

Thanks so much...

Steve

I hold so much 'in reserve'.........let me turn your world up-side-down. Revolutionary.....not 'evolutionary'.

SOLD!!

I just got your video (inland coin and relic hunting one) -- so I will start there...looking forward to the "real thing" in the future. Very, very much appreciated, sir!

Steve