gold nugget simulation?

[green]

Aluminium can sheet, coins, bits of wire, are not suitable representations of nuggets. Modified coins maybe a possibility.

The 'models' need to be homogenous, comparable in size to the real thing, having representative ease of detection and time-constant/corner-frequency. (from reply#16 Gold Results)

For detector comparison I'm still wondering if copper wire wouldn't make a good standard target for short TC targets(1 to 10usec). Should be available for everyone. Cutting a 20mm piece or longer should be repeatable. Time-constant/corner frequency is most important with a PI. I like regular strength aluminum foil(around 25mm square)maybe 1, 2 and 4 layers as another option. Cutting a 25mm square should be fairly repeatable, not sure if regular strength foil is the same everywhere. Compared two pieces 1 inch square(one Reynolds wrap and one Wall Mart brand)charted almost identical.

Did a test with some AWG19 copper wire. Cut 3 pieces 20mm long, cut one in half for 2pieces, cut another in half then in half again for 4pieces to see if they charted the same. Thinking need to determine starting length. Maybe someone could try some different lengths of copper wire sizes AWG22 to AWG16 with there detector.

[waltr]

Did a test with some AWG19 copper wire. Cut 3 pieces 20mm long, cut one in half for 2pieces, cut another in half then in half again for 4pieces to see if they charted the same. Thinking need to determine starting length. Maybe someone could try some different lengths of copper wire sizes AWG22 to AWG16 with there detector.

Interesting result on the different lengths of AWG19 wire. I would have expected the length would make a difference.
Then great of testing different diameters of same length that shows diameter is what matters.

Still unsure of how to simulate gold nuggets.
I do have a few nuggets and my hand waving results are that the smaller nuggets must be closer to coil to detect.
Also has a vial of fines (from dust to very small nuggets) and this is not detectable even though total weight is more than a larger nugget.

Another issue with natural gold is the purity. The conductivity drop drastically with small amounts of other metals in the gold.

[Carl-NC]

I sometimes use solder blobs (std 63/37). I can make any size I want and they are reasonably spherical. Lead shot from shotgun shells also works pretty good.

[Skippy]

I've been busy, and now I'm away for a few days, when I get back I'll see what I/we can come up with for simulation.

[green]

I sometimes use solder blobs (std 63/37). I can make any size I want and they are reasonably spherical. Lead shot from shotgun shells also works pretty good.

What is the smallest shot detected by a good PI at two or three inches with a 8inch diameter coil?

[green]

Interesting result on the different lengths of AWG19 wire. I would have expected the length would make a difference.
Then great of testing different diameters of same length that shows diameter is what matters.

Still unsure of how to simulate gold nuggets.
I do have a few nuggets and my hand waving results are that the smaller nuggets must be closer to coil to detect.
Also has a vial of fines (from dust to very small nuggets) and this is not detectable even though total weight is more than a larger nugget.

Another issue with natural gold is the purity. The conductivity drop drastically with small amounts of other metals in the gold.

With short TC targets(<10usec, most if not all chart straight line decay on linear log chart)I've found TC proportional to width and thickness, not length. Length effects signal strength. With an increase of three wire sizes, resistance doubles, width and thickness are .707 of the larger wire, .707X.707=.5. TC of the smaller wire calculates .5 the larger, same as I chart. If wire inductance stays the same with change in wire size and resistance doubles TC should be 1/2 of larger wire, L/R. Not sure why length normally doesn't effect TC.

[Carl-NC]

What is the smallest shot detected by a good PI at two or three inches with a 8inch diameter coil?

I find most PIs will hit 2-3 grain gold nuggets @ 1-2". Let's say 3-4 grains @ 3".

#8½ shot is ~ 1 grain
#6 shot is 2 gr
#4 shot is 3.3 gr
#3 shot is 4.4 gr

So #4 shot on a really good PI, #3 shot in a bad day. #3 is hard to find. 8½ also. This is why I prefer solder blobs.

[dbanner]

How about making some pure gold blobs for testing. Then you'd have a standard platform for everyone to compare results. Not all solder blobs are equal( depending on type of solder available at local shop) . Shotgun shells carry a criminal offence in most countries(unless you have a permit which you have to pay for). Naturally occurring gold nugget is so varied in shape impurities etc. A spherical gold blob seems reasonable, which you could lightly tap with small hammer to achieve some flatness of a predetermined amount(if required). Then everyone can have identical samples for testing.

[dbanner]

Send

[green]

Has anyone tried a piece of AWG22(TC=1.3usec) or AWG20(TC=2usec) solid copper wire to see how long a piece is required to detect at around 3 inches?

[Skippy]

You're forgetting that AWG is obsolescent, and was also mainly used in North America.
Here in the U.K, it's metric, or SWG ( Standard wire gauge).

[green]

You're forgetting that AWG is obsolescent, and was also mainly used in North America.
Here in the U.K, it's metric, or SWG ( Standard wire gauge).

If I did math correct. It does mean, not available to everyone. I would still be interested if someone could try 22 or 20 wire, length for about 3inch(75mm)detection distance. SWG should be a little easier to detect.

[green]

No interest in using AWG copper wire as a standard target. Was thinking available to everyone until Skippy replied it's not. Didn't know if it would make a good test target anyway. Best if target is available to everyone. Eric, King JL, MTammet and myself did some testing with aluminum foil in the vallon thread. Think aluminum foil is a possible target material. Started a chart with different foil targets. Could make one with heavy duty foil(TC about 50% higher). For longer TC targets could try starting with 8x8in or 12x12in square folded 2, 4 and maybe 6 times. My interest is having something to compare the detector I'm making with what a good PI detector would do. If detection distance is a lot less(why and what to do to make it better)? Added some things to fill in that I think should effect detection distance. Are there others that should be added?

IF not used for distance comparison, the chart does list targets with different TC, some with the same TC at three different sizes to test the detector with. Just some thoughts for discussion. Should we start a new thread, maybe standard test targets?

[waltr]

IF not used for distance comparison, the chart does list targets with different TC, some with the same TC at three different sizes to test the detector with. Just some thoughts for discussion. Should we start a new thread, maybe standard test targets?

Sounds like a good idea. Please do measure the foil thickness so we can match the foil used.

A possible issue is the aluminum foil available in different places may be made with different compositions, alloy, which could have different conductivity and effect the TC.
This difference may also be among different brands of foil in the same store.

[Skippy]

Stop it. The only new thread 'sort-of' needed is the "finger ring" thread.... which I'll get on with in the next week.

Regarding the copper wire: I will have a rummage and see what 'coat-hanger' ECW I have, obviously for VLF testing, so just general interest, results will belong in the other 'test target' thread.
And just fer interest - while AWG has the cunningly designed feature of a constant diameter ratio from one gauge to the next, hence your plots of TC vs. gauge making sense, SWG only approximates that, and varies in a blocky non-linear way, so you can't create charts using the gauge number, you have to use the physical measurements, diameter, CSA.

Back to the nugget simulation.
Mr. Green.. we need to analyse your sample nuggets more, one thing we need to know is their volume. Do you have weighing scales accurate to 0.01 gram ? Do you have very thin mono-filament fishing line, say 0.1 mm diameter ? This is the size that has breaking strain of 4 lb / 2 kg. Or very fine copper wire, such as 0.05mm, 0.003 inch, 44 SWG , 40 AWG ?
I'll post up the method later.