DOD coil design for old pulse induction?

[Nova]

G'day all, just wondering will this coil design work on pulse induction or not, was thinking maybe it could help improve sensitivity on these older machines like SD series, what is your opinion?

[Carl-NC]

Sure, it can be made to work. Somewhere on Geotech there is a thread where someone was building a DOD, I forget who but it was long before the GPZ was introduced. Not sure it'll improve sensitivity.

[Nova]

Thanx Carl, will see if i can find it, so are u saying that coils have little to do with improving sensitivity, ( it's more to do with the type of pulses and electronics?) and could u give me a brief explanation as to why the the Sd series of minelabs lack the sensitivity to the smaller gold in general, in comparison to the gpx machines, i understand ZVT is a newer tech( or is it?) these machines seem like another level up in finding those small nuggets deep, by what i've seen and heard.

[Carl-NC]

Minelab detectors have improved in sensitivity from SD through GP/GPX through GPZ, regardless of coil. An IB coil is necessary on the GPZ because there is no 'off' cycle and they chose to use a DOD. Not sure why, but advantages are better ground and EMI elimination, plus you can edge-detect with either edge of the coil. The SDC2300 is actually more sensitive to sub-grain nuggets than the GPZ even though it is a standard PI with a mono loop. But the Zed will beat it on larger nuggets at depth.

[green]

Minelab detectors have improved in sensitivity from SD through GP/GPX through GPZ, regardless of coil. An IB coil is necessary on the GPZ because there is no 'off' cycle and they chose to use a DOD. Not sure why, but advantages are better ground and EMI elimination, plus you can edge-detect with either edge of the coil. The SDC2300 is actually more sensitive to sub-grain nuggets than the GPZ even though it is a standard PI with a mono loop. But the Zed will beat it on larger nuggets at depth.

https://www.geotech1.com/forums/show...505#post205505 A test I posted awhile back. Rx coils subtracting not good for distance and a null in the center. Wondering what I did wrong.

[Carl-NC]

https://www.geotech1.com/forums/show...505#post205505 A test I posted awhile back. Rx coils subtracting not good for distance and a null in the center. Wondering what I did wrong.

I don't see that you did anything wrong. It should have a null in the center.

[Nova]

Thanx again Carl, i am familiar with the sdc2300 being very sensitive on the small gold, but i'm not so sure it can pick those small one's as deep as the GPZ, by what i have seen the Z is the best on small gold at depth, and also specimen gold, but i know of at least one test that was done on a decent gold nugget at depth with an SD2000d vs the 7 and guess what, the SD smacked it's a-- . This fellow told me that the 7 would beat the SD on depth upto the 1oz mark then the SD would kick it to tomorrow.
I just recently purchased your book Carl, mainly to hopefully gain some secrets, i think i have gained some new things i did not know about, but as far as understanding electronics, it is the same with programming, your brain has to work a certain way to comprehend it, and mine does not LOL, so anyway it was an interesting read, one major thing i did learn was that achieving any decent depth gains is near on impossible, so that kinda sucks, so to have any chance of finding some gold that is left, ZVT is about the only option going forward, an expensive one at that.

[green]

I don't see that you did anything wrong. It should have a null in the center.

But the Zed will beat it on larger nuggets at depth.

I wonder how the Zed gets depth if Rx is wired inverting. I got a large signal loss at distance. What am I missing?

[green]

But the Zed will beat it on larger nuggets at depth.

I wonder how the Zed gets depth if Rx is wired inverting. I got a large signal loss at distance. What am I missing?

Don't know how he Zed does it but I think I could do both. Rx inverted for closer targets, better signal to noise. Rx adding for distant targets.

[Carl-NC]

You want to look at the overall temporal response of the DOD coil. That is, what is happening as the coil is swept over a target:



You get a null at dead center but not for each RX coil. You could, for example, rectify this response and filter it for perhaps an enhanced response. No idea if this is what ML did or not, I have not played with the Zed enough to figure out what is going on. But this is exactly the same method I use in designing a security walk-thru detector.

My (very limited) experience with the SDC is that it will pick up smaller sub-grainers (say, 1/4 grain) than the Zed is incapable of seeing at all. Once you get to multi-grain nuggets the Zed will get them deeper than the SDC. I don't know where the break-even point is.

[Nova]

Okay Carl, that makes sense, i have just one more question for you in regards to ZVT, does Minelab have a patent on this tech?, if not, should we expect to see some other companies with their own version of this soon, i would hope so, and at a more reasonable price, like 5-6k max?, my experience tells me, at least in the Victorian goldfields of Australia, that the big gold is either been found or is nonexistant, so the tech going forward must focus on getting those smaller pieces deeper, and ZVT is currently the leader in this respect, so only continual improvements of this tech will see a future for the detection of these goldfields!!

[Carl-NC]

Minelab has a patent on ZVT. But I know at least 2 other ways to make a constant-current PI design that avoids the patent. White's has a patent on a method and I did some work with that when I was there. Probably you will never see it produced. The other method I know of, I cannot discuss.

[Nova]

That a shame to hear Carl, so at the moment Minelab has a monopoly on the market, competition would get the price down and allow access to a fair percentage of the market who are currently financially discriminated against owning this tech.You say you know a method Carl, it would be great to get this to the market if not by you, by another company, what do you say to that?,if you don't want to comment any further, i fully understand!
Cheers!

[Carl-NC]

Minelab has a lot of patents but that alone doesn't stop competition when there are other ways of doing things. Multifrequency and PI have been done by competitors, and CCPI could be, too. What stops competition is the will to embark on the high-risk and high-cost development of new technology. Companies like White's and FTP don't have an R&D group, I doubt Garrett does either. Their focus is on getting real products out the door which means 'don't go far from what we know how to do.' Minelab probably has a pretty healthy R&D group, that's why they lead in technology and patents. And, that gives them the right to charge whatever they want. People who don't want to pay the price can certainly choose not to.

Eventually someone will produce a lower cost CCPI design to compete with the GPZ. If not a competitor, then Minelab itself, the same way they did with multifrequency.