Metal Densities And Conductivity

[stupot]

An excellent set of replies and information. Especially for those who think below ground as well as above.

There is a possibility of future technology analysing this, as there is currently. But not to the degree of dealing with the many facets of detecting in the real world.

Everything is possible at some point.

Great discussions! Thanks to all.

[IBMe]

The density is in the tone and easy to test. Stack two bottle caps, do a swing. Put a gold ring in the bottle caps and do a swing. But it’s a different scale than the conductivity scale. To some extent you can gage it with your ear but that’s pretty iffy.

But if the CPU in the detector was watching it and gave you a beep at a density setting, no telling how much more you’d be finding. The good stuff is more prevalent in the trash, thus all kinds of noise.

Give me a density reading along with conductivity.

Also, give me target width, which the Garrett GTI 2500 did. Needs a modern implementation.

LOL, the Garrett GTI 2500 would even talk to you. Take a pass on that.

[PimentoUK]

Quote: "Formula on conductivity was off several sites and all had a value*log7 or log6"

The values are in error, probably the factor of 10 got overlooked. Silver and tin are nowhere close, about 106% IACS and 15% IACS, respectively.

And yes, working from memory, I got tin and lead wrong, tin is about twice the conductivity of lead, not half. The hazards of having resistivity AND conductivity as commonly used figures.

Here's a pretty comprehensive list of metals/alloys and their electrical characteristics:

 

https://www.effectrode.com/knowledge-base/conductivity-of-metals-sorted-by-resistivity/

 

If I can track down my 'fake dollars' thread on Tom D's OLD forum, I will add a link here.

It took some sleuthing, but here it is:

"Make your own fake gold dollars"

https://www.dankowskidetectors.com/discussions/read.php?2,27267,27267#msg-27267

 

 

 

 

 

 

 

[GB_Amateur]

21 minutes ago, PimentoUK said:

"Formula on conductivity was off several sites and all had a value*log7 or log6"

The values are in error, probably the factor of 10 got overlooked. Silver and tin are nowhere close, about 106% IACS and 15% IACS, respectively.

And yes, working from memory, I got tin and lead wrong, tin is about twice the conductivity of lead, not half. The hazards of having resistivity AND conductivity as commonly used figures.

Here's a pretty comprehensive list of metals/alloys and their electrical characteristics:

 

https://www.effectrode.com/knowledge-base/conductivity-of-metals-sorted-by-resistivity/

A couple comments about this listing of resistivities and conductivites on the linked webpage:

'IACS' stands for International Annealed Copper Standard.  Thus the value in that column is conductivity relative to a particular form of (pure) copper.  ( @kac if you redo your plot, this would be a meaningful value to use.  Most everyone has a 'feel' for where copper hits on their detectors.)

It would have been nice if they had included the temperature at which these measurements were made.  After quick spot check of values, comparing to those I have (see link in my first post of this thread), it appears the measurements were made at an intermediate temperature between water's freezing and boiling points, probably somewhere in the 'room temperature' range (20 C --> 30 C) is my guess for a typical measurement.  Note that conductivity goes down as temperature goes up, although there may be some exceptions to that.  Nature likes to throw us a curve ball every once in a while.  🙂 

[John SC]

Very interesting info, maybe muli-frequency on multi-frequency. One set of selected frequencies reading resistance one set reading conductivity? I really wonder what the next big improvement is going to be. 

[Geotech]

1 hour ago, IBMe said:

The density is in the tone and easy to test. Stack two bottle caps, do a swing. Put a gold ring in the bottle caps and do a swing. But it’s a different scale than the conductivity scale. To some extent you can gage it with your ear but that’s pretty iffy.

I think that's not really due to density. What detector are you using for this?

[IBMe]

The best for hearing density of target, F5, no longer have. Have orx, d1, nox600, legend, F75 and others. Sound is a personal thing, have to play around to find something that works for you.

Do the actual test. You have to ignore number ID and tone ID, just the density of the tone. Dense objects have a heavy sound, thin objects have a light sound. If the object is bent, then you can’t tell.

A D1 in full tones is pretty good.

Slowly move dense and non-dense objects over the coil and listen. Easy to tell the difference.

Density also affects the width. An aluminum cap and quarter are about the same width. The aluminum cap will have a lot wider sound than the quarter. You may have to raise the coil to get a better sound profile. The Garrett GTI 2500 had a width readout. Wider for caps.

This only works for flat objects. Different shapes may distort the results.

A dense object has more consecrated mass, heavy sound. A non-dense object has less consecrated mass, light sound.

 

[Geotech]

An aluminum cap has side walls that extend the eddy response beyond that of the much thinner quarter. Try comparing the aluminum cap with, say, a 3/4" copper pipe cap. Or compare the quarter to an aluminum coin, like an Italian 10 lire which is almost the same size.

I'm trying to think of a decent aluminum ring that would closely match a typical gold ring. Saw off a very small length of aluminum pipe I suppose. If you compare an aluminum ring with a gold ring, similar sizes, you should find that they have the same kind of sound. It's all about the tau and the physical shape of the target, not the density of the metal.

[IBMe]

3 hours ago, Geotech said:

An aluminum cap has side walls that extend the eddy response beyond that of the much thinner quarter. Try comparing the aluminum cap with, say, a 3/4" copper pipe cap. Or compare the quarter to an aluminum coin, like an Italian 10 lire which is almost the same size.

I'm trying to think of a decent aluminum ring that would closely match a typical gold ring. Saw off a very small length of aluminum pipe I suppose. If you compare an aluminum ring with a gold ring, similar sizes, you should find that they have the same kind of sound. It's all about the tau and the physical shape of the target, not the density of the metal.

Sound is a personal thing; everybody has to come to their own conclusions. Just tried a gold, copper, silver, steel and aluminum ring about same size and thickness using nox 600 and 1 tone. The gold ring has a heavier sound.

Tried Park 1 & 2. Most notable on a really fast swing, gold ring has a little more pop to it.

The gold and silver have a little extra sweet sound, kind of a little after ring.

Is it density or composition, or both? I don’t know, but the difference is there.

 

How much attention do the masters of musical instruments pay to materials?