gold nugget simulation?

[green]

Plotted distance vs amplitude. Both charts show similar amplitude for the 10 grain nugget and the (10 grain) lead and aluminum (similar size and shape, not weight) at short delay times. It appears that shape and size control signal strength for targets made of gold, lead and aluminum at short delay times. Maybe not?

[Funfinder]

Why not buy a few mini-pages of leaf gold (its not that expensive because its extremly thin)
and wrap it over very small nuggets-shaped alu-balls? Would create pretty authentic results.
The main signal-creation work gets done by skin-effect, so 2 layers of leaf gold should work.

[Chet]

Plotted distance vs amplitude. Both charts show similar amplitude for the 10 grain nugget and the (10 grain) lead and aluminum (similar size and shape, not weight) at short delay times. It appears that shape and size control signal strength for targets made of gold, lead and aluminum at short delay times. Maybe not?

Hi green, very informative chart. Was it possible for the 18 grain nugget and the 9mm x 9mm aluminum target to proceed down to 9 or 10 inches? Is the vertical axis in millivolts or some other reference scale?
Thank you,

[green]

Hi green, very informative chart. Was it possible for the 18 grain nugget and the 9mm x 9mm aluminum target to proceed down to 9 or 10 inches? Is the vertical axis in millivolts or some other reference scale?
Thank you,

Hi Chet. The first digit is 100 uv. Thinking of trying another plot. Maybe add some different size lead shot. It looks kike if you can detect lead, gold of the same size and shape should be easier to detect. I'll plot the targets out farther.

[Chet]

Hi Chet. The first digit is 100 uv. Thinking of trying another plot. Maybe add some different size lead shot. It looks kike if you can detect lead, gold of the same size and shape should be easier to detect. I'll plot the targets out farther.

Hi green, thank you for the answer back. Since the conductivity of gold and lead are different it might be interesting to see how they compare if the lead was scaled up in size?


Perhaps you could try to match the 10 grain and 18 grain nuggets with similar pieces of lead.

[baum7154]

Looking at your charts raises many questions and observations.

Your 4 grain gold sample detection distance is in the neighborhood of the detection distance of a 4.5 grain piece of 14 kt jewelry gold using my CHANCE PI detector, somewhat less.

I believe the 'volumetric equivalent' method described on the first page of this thread (.7grains of AL = 5 grains of AU) should also be applied to lead simulants. Is this what you are doing in your tests?

Since gold is 1.695 times more dense than lead 2.948 grains of lead = volume of 5 grains of pure gold.

Once a simulant material is calibrated to the desired volume/grain weight of gold it can be pounded into a thinner sample in order to present the desired area and thickness of a given gold nugget.

In order to present the smallest area in my distance tests using aluminum simulants I just left them as cylinders and did not pound them out. I believe that the smallest area presents the most difficult target to detect especially when using small pieces of short TC materials. Since the metallurgical makeup of any nugget likely contains 'slower metals' I assume that using pure gold in these calculations represents a worst case.

Regards,

Dan

[green]

[Perhaps you could try to match the 10 grain and 18 grain nuggets with similar pieces of lead.]

[I believe the 'volumetric equivalent' method described on the first page of this thread (.7grains of AL = 5 grains of AU) should also be applied to lead simulants. Is this what you are doing in your tests?] Yes

More charts: The aluminum target was cut from an aluminum roofing nail. The distance vs amplitude chart was made to show trends. The detection distance is limited by my circuit.

[Chet]

Hi green, looks like the surface area of the lead makes quite a difference. It appears that a lead test target will provide a good test for a fast coil and ability of a detector to receive and process early samples.

Attached is a reference chart from Eddy Current testing; Interesting on how far apart Lead and Gold are in conductivity.

Also notice how many different aluminum alloys were tested.

[Funfinder]

@ green
Maybe your efforts are useless because the signal changes with the targets size
and every PI is different. Below the whole issue is described pretty good.


at the end of the page:
http://www.nuggetshooter.com/article...detector2.html

Due to the nature of the signals caused by different objects, it is extremely difficult, or put another way, almost impossible to build a good discriminating PI. Since the time it takes for a target signal to decay can vary because of the size, shape, and chemical makeup of the object, then any type of later sampling will not produce a reliable form of discrimination.
Many PI's rely on the ability of an adjustable delay whereby the operator can simply adjust the delay longer to see if an object is a piece of gold or not. If the delay is increased and the signal from an object disappears, then the operator can assume the object is made of a lower conductive material such as gold. This is acceptable for those hunting something like gold rings, but does not work well on gold nuggets. larger gold nuggets can produce a much longer delay, so any attempt to use this delay technique will result in one thinking a large gold nugget to be junk.

Another concept used on a PI for discrimination is to sample during the "on" time of the pulse. Any target will produce a slight change in the signal seen at that time as well as a change when the normal target sample is taken.
If the analysis is done correctly, then one can use both the "pulse on" and "pulse off" signals and get a better analysis of a target. This type of design can lead to a better form of discrimination. However, few if any PI's are actually using this technique.
Regardless of the technique used, no form of discrimination is perfect, and, most likely, never will be. Some techniques are better than others, but all can be fooled, and this is true of both PI's and VLF's.

[green]

Plotted the gold nugget targets again. Plotted with sticks flat and rotated 90 degrees. Funfinder is right, everything changes. The 4 grain nugget flat has the same TC as the 18 grain nugget on edge. Time constants varied from 1.9 to 6.6 usec When I started the thread I didn't have any idea what the TC might be.
I guess my question was how soon do I need to sample. Smaller or thinner nuggets would probably have a shorter TC. I think from the testing I've done a target made of aluminum the same volume and shape as a gold nugget would have similar amplitude and TC. Lead seems to work at early sample times, but I think I would use aluminum.

[Chet]

Hi green;
Good information in your chart as usual. In my experiences in nugget hunting it is rare to find aluminum or coins. Quite a few lead bullets and small lead scraps from soldering are found.


But the big headache is small leather boot nails and other small pieces of rusted metal. There are hundreds of square nails from picture frame size to 4” spikes.


I am working on software ideas for discrimination between ferrous and nonferrous based on time constants. I’m not concerned with missing that rare silver or copper coin.


So the questions I have are:
Do small pieces of iron similar to the 18 grain nugget have longer time constants than gold?


How do large similar targets ½-1 oz of aluminum, lead, copper, silver and iron compare in time constants?


The thought here is from some of your charts the time constant for small pieces of aluminum and lead are similar to gold. If this holds true for large size pieces and the iron time constant differs enough there is something for the software to work with.


Thank you for any help that you can provide on this,
Chet

[green]

Hi Chet,
Charted some nails. Don't know if they match what your finding. The decay curves aren't straight. Check the slope at the sample points your using.

check your PM

[baum7154]

Hi green;
Good information in your chart as usual. In my experiences in nugget hunting it is rare to find aluminum or coins. Quite a few lead bullets and small lead scraps from soldering are found.


But the big headache is small leather boot nails and other small pieces of rusted metal. There are hundreds of square nails from picture frame size to 4” spikes.


I am working on software ideas for discrimination between ferrous and nonferrous based on time constants. I’m not concerned with missing that rare silver or copper coin.


So the questions I have are:
Do small pieces of iron similar to the 18 grain nugget have longer time constants than gold?


How do large similar targets ½-1 oz of aluminum, lead, copper, silver and iron compare in time constants?


The thought here is from some of your charts the time constant for small pieces of aluminum and lead are similar to gold. If this holds true for large size pieces and the iron time constant differs enough there is something for the software to work with.


Thank you for any help that you can provide on this,
Chet

____________________

I thought I'd add some info from time spent in the field with a CHANCE PI:

On several occasions small flakes of iron rust and even a thin rusty old razor blade showed up as an indication of small gold. Also I run into a lot of aluminum can debris from streams that has been broken down into chips that show as gold. In my opinion it is inevitable that the aluminum displays as such.

Regards,

Dan

[Chet]

Hi Chet,
Charted some nails. Don't know if they match what your finding. The decay curves aren't straight. Check the slope at the sample points your using.

check your PM

Hi green,
Great information, looks like a time constant around 9 might work as a discrimination point.
Thank you,
Chet

I didn't find anything in my PM.

[Chet]

____________________

I thought I'd add some info from time spent in the field with a CHANCE PI:

On several occasions small flakes of iron rust and even a thin rusty old razor blade showed up as an indication of small gold. Also I run into a lot of aluminum can debris from streams that has been broken down into chips that show as gold. In my opinion it is inevitable that the aluminum displays as such.

Regards,

Dan

Hi Dan
Thank you for the information. Do you know what characteristics the Chance PI uses for discrimination? Is the software is controlled or is there a description of it somewhere? Does it have ground balancing? How well does the discrimination work on ferrous objects?
Thank you,
Chet