Pulse Devil testing delayed again

[prospectinginoz]

No way Doug I don't know were you came up with this idea, but If YOU have done any hunting you would know ALUMINUM is so far off GOLD there is no comparison. I have only seen aluminum used to agzagerate a detectors depth capability in the past. Good luck

Are you saying then that Eric Foster is wrong in recommending AL blocks to us for depth testing Pi detectors as a substitute for gold nuggets?

What do you think are the most critical factors that control depth and sensitivity for conductive targets with Pi detectors?

If AL as suggested by Eric Foster is not a good substitute for gold nuggets then what do suggest we use and on what basis?

By the way our Goldfields in Vic, Australia contain very little in the way of Al pull tabs or tops or foil. I have been hunting since 1981.

Where possible we ALWAYS use natural gold nuggets (up to 19ozs) for our depth testing. However for testing at big depths this is not practicable (or secure!) as we would need nuggets of 100ozs and upwards.So we need to find a good substitute.

best regards

Doug

[prospectinginoz]

No way Doug I don't know were you came up with this idea, but If YOU have done any hunting you would know ALUMINUM is so far off GOLD there is no comparison. I have only seen aluminum used to agzagerate a detectors depth capability in the past. Good luck

Electrical conductivity x 107/W m at 295 Deg Kelvin (the bigger the number the more conductive the metal)

Aluminum=3.65

Gold =4.55

Lead =0.48

Silver =6.21

Copper =5.88

Iron =1.02

Zinc =1.69

Therefore the closest metal to pure gold in conductivity=Aluminum. Iron is closer to gold in conductivity than lead.Native gold may have a lower conductivity than pure gold of course which would make it even closer in conductivity to pure aluminium.

Data from: Kittel, Charles, Introduction to Solid State Physics, 7th Ed., Wiley, (1996)

Doug

[montana]

Reg. Saturday was great and a huge learning experience for me. I can hardly believe we talked most of the day away. It gave me a lot of insight into what drives a person to not only build their own PI detector , but the coils to go with it. I'm not nearly so skeptical that some big breakthroughs could come from a home workshop on a shoestring budget. Brains, knowledge and a passion for nuggethunting can be a potent combination. I did miss seeing Jim . Apparently he had already left for home.

The late afternoon nugget hunt was dismal with what I consider the worst possible detecting conditions. Saturated surface soil with dry dirt down about 4 inches. I was lucky to get that shallow tiny nugget just before I ran into you in the morning. Have a safe trip home.----Bob

[wyndham]

Remember the song "Fools rush in where Angels fear to tread"? Well just a thought on the Al vs lead, silver, iron or other metals. Al has a diamagnetic property as does gold and there is something about the way eddy currents may behave that is different than other metals. It may be different than simple conduction and one site I found refered to Al as a damping agent to the eddy current induced by very strong magnetic field. This maybe apples and kiwis comparison or it may have some merit.

Like I said I'm not a PI engeneer, I just wish I were. Wyndham

[AZNuggetBob]

Doug We are on two different pages here. Im refering to aluminums ability to reflect an electromagnetic feild.!! Not its ability to conduct current. Granted it cunducts electricity very well. This is why they use it as sheilding in coaxial wire. It blocks EMF which also makes it upset a metal detectors feild very well. AzNuggetBob

If what your saying is true why not use aluminum wire to wind a coil? Or how about silver?

[prospectinginoz]

Doug We are on two different pages here. Im refering to aluminums ability to reflect an electromagnetic feild.!! Not its ability to conduct current. Granted it cunducts electricity very well. This is why they use it as sheilding in coaxial wire. It blocks EMF which also makes it upset a metal detectors feild very well. AzNuggetBob

If what your saying is true why not use aluminum wire to wind a coil? Or how about silver?

Why not use Silver or Aluminium wire.But conductivity is only one criteria for coils.Inductance and coil capacitance and shielding and Q are probably more important. Some people have used silver wire and one person even suggested using gold wire! Our testing with 3000's and 3500's shows that Al blocks do behave somewhat like native gold. The big advantage of Al blocks is that Eric Foster has calculated the time constants based on the dimensions of the blocks. For our testing purposes this is very useful as we want to see what happens to the depth of the ML Gp series when we use objects whose time constants are much longer than the transmit pulse length. Metals including Al reflect to some degree EM fields but he ability to readily induce eddy currents with EM fields is primarily determined by the metals conductivity.

doug

[Reg]

Hi Sourdough,

Reg, can you post some pic's of what these invisible nuggets look like? Are thay porous (sp) or something different all together? I've heard of them but never seen one. No pun intinded.

I can try to take pictures of the couple of "invisible nuggets" but the man with the best pics of them is John Blennert. He posted some pics quite a while back on the nuggetshooter forum so you might ask over there also. I couldn't find them when I looked. Maybe he will read this and post some of his pictures.

How about it John, you out there? Can anyone out there get in touch with John? I tried some time back but didn't have any luck.

Does anyone know the name of John's website and if he has pics of the invisible nuggets on it?

As for me taking pics, I don't have my camera with me so it will be a while before I can post anything. Also, the two I have are not that large, but are large enough to be deceiving.

The two nuggets I have have a fine grain or almost a needle structure and when closely evaluated appear to be quite thin gold wise. This would account for their ability to hide from PI's.

Reg

[Reg]

Hi Montana,

It was a pleasure to meet and talk with you also. I don't get to hunt for nuggets as much as I like and have learned to rely on people like you and Rob to provide me with the tricks of the trade. You guys do know your stuff. I just wish I knew half as much about the specifics of nugget hunting as you guys do. It is certainly understandable why you find nuggets on a regular basis.

You may have not noticed it, but I was listening very carefully when you were discussing some of the techniques you use and what you look for when hunting for nuggets. I just hope I can remember all of what you mentioned.

BTW, I talked to the guy today that you helped and he was much happier with his detector. Obviously, you were able to instruct him what he needed to know because he was upbeat and happy.

Reg

[Reg]

Hi AZNuggetbob,

I know we usually use lead as a substitute when testing, but when trying to simulate large gold, it is best to try to match the time constant of the material if you are going to use a substiture for the simulation to be as accurate as possible. In the case of gold, the best match is aluminum. Now, this would be a pure aluminum ingot which will respond much different than something like an aluminum can.

Eric Foster did a lot of experiments when he worked on the PI project at Oxford many years ago. He is extremely knowledgeable when it comes to what works best and what to expect. As an example, quite some time back he discussed what happens to the signal from gold and silver as they are combined. He ran tests and the results were quite suprising how the different alloy combinatons affected the ability to detect them.

Reg

Hey Rob,

It was great to see you again. Now, next time I get the tab for breakfast. Enough is enough, but thanks anyway. It was great to see Dennis again also.

I am glad you found at least one nugget today. When it comes to finding them, you are the guy. When you are not looking, I do tell people to watch what you do because people could really learn a lot.

Reg

[AZNuggetBob]

Hi Reg, That would explain why aluminum cans seem to be the most detectable aluminum. even aluminum coins are compressed when they are struck. Possibly the compaction of the molicules during the manufacturing proccess ?. And allowing differences in natural nuggets from around the world would seem that it would be impossible to get a fair assesment useing them. Do you think maybe the best targets would be pure gold ingots of varying sizes? AzNuggetBob

[Reg]

Hi AZNuggetBob,

I am going to try to expand my answer for a wide audience. So, it may seem basic to you but my answer is meant to try to inform others who may not have extensive knowledge of the specifics involved.

One of the reasons I mentioned the alloying of silver and gold is that is what happens in nature also. Generally, a gold nugget is not pure gold but a combination of metals with gold as the primary metal. Now, the ability to detect the nugget can change because of this different combinaton of metals.

There are other things that influence the ability to detect a nugget including the surface characteriestics, the actual physical makeup of the nugget, and the positioning or plane of the nugget. If the surface is nice and smooth we can get a certain signal level back. If that same surface is rough and irregular, the signal can change. If the nugget is very solid it will or can cause a different signal than one that is porous. A nice slug lets say is the approximate size and shape of a quarter will give different signals when the nugget is lying flat that it will on edge.

So, it is extremely difficult to try to test or determine something like depth characteristics of what to expect and get an exact answer. Therefore, to get a relative idea, we could substitute a simulated or a man made "nugget". When we create something to take the place of gold, we should try to find a material that has similar characteristics as far as the signal from the coil is concerned.

In the case of a PI, the general recommended material will have what is called the time constant of that material. In the most basic terms this means the signal from the coil will cause as almost the exact signal inside the material being tested.

As an example, the penetration level changes with the conductivity of the material. A material that is much more conductive will allow the signal to go deeper into the material. This equates to a longer time constant. So, the time constant of gold is short when compared with silver. Alloy the two and things change.

Increasing the size of the object being tested generally has a longer time constant as does the the material's density or phrased differently, how solid it is.

A material with a longer time cnstant generally needs a longer pulse length if one is trying to obtain maximum depth of detection. This is why silver objects of similar size as gold objects may not appear to be detected quite as deep if the pulse length of the detector is a constant. Also, larger gold objects with similar characteristics will require a longer pulse length if one is trying to find out just how deep it can be detected.

Unfortunately, my long winded explanation really didn't give you a specific answer because there is no specific answer. We have no way to properly substitute even gold ingots to try to simulate what to "exactly" expect. What we can do is get an approximation and that is what testing does. Also, something like an ounce of small gold nuggets will not come close to responding the same as a nice solid ounce nugget.

We can test for depth using a nice large solid mass of gold such as a gold ingot or slug but that will not tell us exactly what a really large specimen will do if the gold within is not solid or continuous in the specimen. So, we could have a huge gold specimen that can't be detected nearly as deep as a solid piece of gold having much less gold.

So, all we can do is make an approximate test and hope for the best. In doing so, we generally use the material that appears to be the same or very similar as far as the coil signal is concerned. Since solid aluminum has a similar time constant as gold, it does work to give us an idea of what to expect

Reg

[AZNuggetBob]

Actually Reg your long verson answered several questions I had about Time constant, Pulse length. Take care, AzNuggetBob

[29prospector]

Reg,

I've been following this post from the beginning and also the one on OZ. I have learned alot of good stuff and have also found out that there are a lot of cry babies running around. In my opippion, the only thing I see that Dave has done wrong, put his work and heart out on the table to see. This to me took guts, yse there are delays, but, unlike Microsoft, Dave wants to get it right instead of letting the public work out the bugs. There are still going to be minor bugs but at least they can be addressed easily.

O'29er in 29

[Wirechief]

Hi Bob and Reg, I'm with you Bob and it does take a lot of courage to do this whole thing the way Dave has. It is really an interesting project and I would love to keep seeing info posted on the Pulse Devil. I also enjoy your posts Reg. How have ya been Bob? I hope the gold mine is doing well! What do you think about the Minelab Extreme that you got to use Bob? Ok fella's take care and God Bless!

John Tomlinson,CET

John's Detectors

[nuggethunting]

Hello Reg,

It was great seeing you and your Father once again. No biggie on the breakfast, it's the least I can do for all the information you share to all of us.

I really thought push 2 would produce more nuggets, but I don't think the dozer got as deep as normal. I was trying my hardest to find a good target (potential gold nugget) so I could have your Father dig it up. However, the nugget I found sounded like trash and was right next to a scared up Granite rock, so I thought for sure it was just another piece of the dozer track.

Like always it was great seeing you again. Everyone really enjoyed your demo and talk about PI's on the claims.

Talk with you later,

Rob Allison

[Goldman]

While the AL blocks maybe close to gold in signal return, the unknown always has to be the ground matrix and the magnetics caused by the pulse frquency. The testing I assume is not in undisturbed ground nor posible, any ground matrix can have an unpredictable effect on the signal, testing is useful to a degree, but the variables of detector, operator and ground makes for some very interesting results or non-results. Don

P.S. sorry I missed you Reg.

[prospectinginoz]

While the AL blocks maybe close to gold in signal return, the unknown always has to be the ground matrix and the magnetics caused by the pulse frquency. The testing I assume is not in undisturbed ground nor posible, any ground matrix can have an unpredictable effect on the signal, testing is useful to a degree, but the variables of detector, operator and ground makes for some very interesting results or non-results. Don

P.S. sorry I missed you Reg.

The ground we test in Vic Australia is undisturbed (by man) except for the small diameter horizontal holes ( which we then line with plastic pipes) bored into the banks of undisturbed gullies in the goldfields. We now have a number of such sites where we at some future date we will be able to compare results on the same target,same detector,same coil etc but different ground matrixes. This I believe is a close as you can come to the real deal and to my knowledge is unique for the non commercial detecting sector. We have found that over many years of testing at the Dunolly site that the results we get reflect very well what happens in the field. Both coiltek and nuggetfinder use to the test site to evaluate their new coils before market release.

Doug

http://groups.yahoo.com/group/ProspectinginOz/

[montana]

Reg. That fellow that was having trouble ground balancing was the second guy I've run into with the same misunderstanding. It's impossible to ground balance an SD when you run the threshold silent. You also have to GB each channel seperately which he wasn't doing. It's no wonder he hadn't found any gold in 5 years of trying. Just one more case of not buying from a dealer who will give you a lesson. He had some pretty incredible stories didn't he?----Bob

[AZNuggetBob]

Im sure you know all this Bob, But Im going to try and describe this for the rest of those people out there still swinging Minelab SD"s That are not sure.That's one of the reasons I like Reg's comments clear and easy to understand. Anyway I run a SD 2100, and not only is it impossible to ground balance silent, your giving up a lot of sensitivity and depth with your threshold to high or to low. Mine runs best right between silent and a solid threshold tone. Just breaking up sound. You can't manually ground balance what you cant hear on an SD. And if your only atempting to balance only one channel than you will be hearing false signals from the other unbalanced channel. Probably why he's turned down the threshold is to avoid all the false signals? Be sure to return the toggle switch back to the center positon after ground balancing both. AzNuggetBob

And like montana said get your metal detector from a dealer that provides feild instruction.

" Having the best metal detector, Great. Knowing how to use it, Priceless"

There are advantages to running your SD in fixed with the ground balance switch in the up or down position. But its a give and take option, and you need to know were to use this. I may get into that later.

[montana]

Aznugget Bob. I can only imagine how many nuggets he missed. When we tried a test nugget they way he was running it there was no response at all . After I played with it a few minutes there was no doubt there was a nugget there. He was attempting to ground ballance with the GB switch in the center position and totally silent threshold. He said that he sent it back to minelab twice and they sent it back saying there was nothing wrong with it. There was nothing wrong with it, just operator error. You have to wonder how many others are out there that don't realize how badly they are setting up their detector. I ran into this all the time when I was giving lessons. Everything from the coil wire in a tangled wad on top of the coil to thinking that the auto tune button on the GPs was ground balancing the detector. ----Bob

[nuggethunting]

Hello Montana Bob,

Well I ran into the same guy your talking about. He stated you gave him some good pointers. However, I have spend several hours with this same guy, then the next time I see him he is doing just the opposite of what I tell him! : He wanted me to check out his detector again and I told him NO, there is nothing wrong with the detector, just get out there and hunt!!!

Not to be rude, but the guy don't hunt more than 15 minutes. I told him he needs to hunt hard, keep the searchcoil close to the ground and listen for fainter targets. However, 10 minutes later the searchcoil finds it way 3-4 inches off the ground ...

We can only give the person the best advice, but it's a matter of them applying those techniques.

Talk with you later,

Rob Allison

[montana]

Rob, I suspected this might be the case, but was hoping for his sake that he learned something. Some guys just can't get it and probably never will . He did seem a little strange. He told us he saw the Hassayampa flash flood when it hadn't rained in months in Az. but it rained that day in Washington. He said there was an underground river connecting Arizona to Washington. This may explain his confusion with the detector.----Bob

[AZNuggetBob]

Hey Rob I used to give lessons to people that were swinging the coil a foot off the ground. I used to tell them that for every inch they hold their coil off the ground their loosing an inch of depth which is not exactly true if you consider ground mineralization but it would get the point across anyway. That wad of coil wire was a good one Montana. Point is I dont see a lot of posts that cover the basics for newbi's. Everyone is preocupied with technical stuff. Best advise Join a club or get personal lessons. I think clubs should have days were they hire a pro for the newbi's ?? I'll probably here about that coment. AzNuggetBob

[montana]

AZnugget Bob. The 24K club has some kind of agreement with Rob for just such services. As he said , he tried to help this guy also. Also the Roadrunners , GPaa, and a couple of other clubs have experienced detectorists come to meetings for talks and Q&A sessions. There's a lot of help out there nowadays with the forums and the internet, clubs, and dealers who offer training.---Bob

[AZNuggetBob]

Hi montana, I used to do seminars for 24K, As Im sure you know many people dont want to get up in front of a group and ask what they think may be stupid questions. Thats probably the number one reason many people prefer private instruction and Most dealers are charging extra ( A lot) extra for personal training. Maybe Im wrong, This may be old news but Ive heard some clubs charge extra to attend seminars when a pro is hired to help cover costs. And a lot of people dont have internet access. I guess videos might be good option? AzNuggetBob