Pulse Induction Discrimination 20 Plus Years And No New Breakthroughs

[RONS DETECTORS MINELAB]

I am also hoping for better small gold discrimination on a PI detector, but as Steve has described in the below article this is a hard thing to accomplish.

Even the GPX-6000, GPZ, SDC have all dropped discrimination from it's features probably due to the smaller disseminated gold capabilities it's after and the fact that these latest Minelab detectors are more of a true gold detector vs. a multipurpose gold and relic/coin detector such as the GPX-5000.

Even though the Axiom has small gold capabilities and offers partial discrimination, it is also very limited at separating out two foot deep 3" nails. Please read the following note from the Garret Axiom owner's manual below:

Note: Iron Check is a conservative function. To help ensure Axiom does not misidentify a good target as iron, the iron tone (buzz) will only activate on strong signals. Therefore, small/weak iron targets may not identify as iron. In addition, due to their large, flat surface area and relatively high conductivity, steel bottle caps will typically not identify as iron. Examples of iron targets that will produce the iron tone (buzz) are: a 3-inch nail to a depth of about 5 inches; and a ¾-inch boot nail to a depth of about 2 inches. In highly mineralized areas, Iron Check accuracy may be affected. 

And in the comparison chart from the GP-3000 located below nothing has really changed in this regard over a 20 plus years timeframe.

Miracles can happen, so maybe in the future we will see some new breakthroughs in PI's discrimination capabilities, but so far just some more dig it all.

 

 

 

 

[phrunt]

I think give it time, they're running out of ways to improve performance on detectors and often hold back certain models to ensure viability of other models, what's next? What do we think they can possibly do to make a GPZ 8000 or GPX 7000?

Already models are separating performance that could be incorporated into a single detector by design.  Depth is the GPZ, small targets was the SDC and now it's the GPX 6000, the GPX 5000 is the versatile unit that can do it all but not quite as well in some areas, perhaps by design.   Could they put this all into one detector? I believe so, the GPZ is certainly VERY capable of very small targets with the right coil, I believe in many cases better than the GPX 6000, it also seems to handle difficult ground almost good a the GPX 5000, this is another area the 6000 is lacking, put it in some types of hot rocks and it's a nightmare that the other models cope with fine.  Combine all three detectors best attributes and you have a killer machine.

The final frontier I think is discrimination, can they make these high end gold machines discriminate targets well? Who knows, nobody, that's what inventions are, new technology that doesn't currently exist.  The 5000 at least has semi capable discrimination, they dumped it off the newer detectors but if they put the resources into discrimination I think they could return discrimination into a newer model with good results, it may require new people with new ideas over the old hands.

Metal detectors unfortunately for us have very limited investment into R&D, imagine if they were more mainstream products like mobile phones, Apple, Samsung, Google or any of the big brand names putting massive investment into improving the technology behind them, I'm sure in that instance we would be seeing jumps in leaps and bounds over what we see now, many of the improvements we see now are side effects of investment in technology in other areas, the Bluetooth audio and faster processors, nothing to do with metal detectors and if metal detectors were their primary purpose we wouldn't even see the improvements we do see now, they're designed for other purposes and metal detector manufacturers benefit from that.

I hope in a few years time we are looking back at current non-discriminating gold detectors as primative beasts, I hope we see Target ID's on ZVT, possible? I hope so and if so the coin, jewellery and relic hunters are in for a real treat.

[Steve Herschbach]

I think people overestimate the underlying technology. VLF discrimination is highly inaccurate, and PI discrimination is a joke. The reality is ground signal overlaps with target signals, so simply using ground balance tunes out a certain class of targets. Almost all targets will read ferrous in bad ground under the right conditions, so anyone employing just basic ferrous versus non-ferrous discrimination, even on the best VLF detectors, leaves good targets in the ground that are misidentified as ferrous. This is simply common knowledge among experience gold nugget hunters, and is why many eschew discrimination of any sort. It is also why the engineer nerds at Minelab left off the so-called discrimination on the SDC-2300, GPZ 7000 and GPX 6000. That’s their way of them telling you how well they think it actually works.

That said I like having the option to use discrimination, as long as it’s up to me to decide when and where to use it. Even with the SDC, 6000 and 7000 I cherry pick targets based on tone, so I am using discrimination - my ear and brain. But I don’t kid myself that I’m not leaving gold in the ground as a result, and neither should anyone else. It’s a gamble at best. The targets you leave in the ground, well, you’ll never know what they were. I can tell you this though and it’s a fact - I have dug literally ounces of gold that were left by others as being junk, probably over a pound at least. People who leave stuff in the ground because they trusted their detectors have put thousands of dollars in my pocket, so thanks! 

[tboykin]

I think the best we could hope for would be iron rejection that involves some use of magnetometer. I believe there is a Minelab patent for this - I was researching it when looking into the hybrid half-sine at White's.

The half-sine was interesting but would likely require heavy processing between the PI and vlf signal. I saw a proof of concept version work while at White's, not well but it did turn on and detect targets. I hope Garrett can figure it out, unfortunately the various iterations of it were only documented in handwritten notebooks left in an engineers desk. My NDA/non-compete is long expired, so if they need help I will do what I can.

When the day comes that we get a PI that can truly knock out iron, it will have me revisiting a lot of old sites. I know a lot of prospectors are may be too old to see this happen, I'll try and leave some gold for your kids/grandkids to find...

[klunker]

1 hour ago, Steve Herschbach said:

PI discrimination is a joke.

But Sir! You know how much I love a good Joke.

 So Here's an idea for the jeenyuses.  Induction in iron produces a much stronger field than in non-ferrous metals with the same mass.  Also iron likes to polarize with the magnetic poles of the planet. Also, as Steve said, we all tend to mentally discriminate targets so why can't computer processing do the same while measuring the strength and polarization of a field?

 I'm working on it. Does anyone here have two JJ6LGCC7 vacuum tubes and a 12KV transformer?

[schoolofhardNox]

Since we are at it.... why not just have a PI side by side with a Magnetometer??? Have the magnetometer be the stronger signal. If the magnetometer reacts to the target it is absolutely ferrous, since I think it only reacts to iron. I'm sure to be corrected if that is incorrect. So by default the PI signal must be non ferrous. I would love to see that in a pin pointer if the scenario is valid.

[Chet]

1 hour ago, klunker said:

So Here's an idea for the jeenyuses.  Induction in iron produces a much stronger field than in non-ferrous metals with the same mass.  Also iron likes to polarize with the magnetic poles of the planet. Also, as Steve said, we all tend to mentally discriminate targets so why can't computer processing do the same while measuring the strength and polarization of a field?

 I'm working on it. Does anyone here have two JJ6LGCC7 vacuum tubes and a 12KV transformer?

Having a Radio and TV business in the 1950s I still have hundreds of vacuum tubes. Even an audio amplifier with 6L6 output tubes. Also a few high voltage transformers are among the collection. What kind of cart or wheelbarrow should we haul this masterpiece on. LOL😄

[GB_Amateur]

32 minutes ago, schoolofhardNox said:

If the magnetometer reacts to the target it is absolutely ferrous, since I think it only reacts to iron. I'm sure to be corrected if that is incorrect.

Almost.  A magetometer in motion is sensitive to magnetic field gradiants (i.e. changes) and ferromagnetic materials are something that causes this.  Both cobalt and nickel are ferromagetic, along with iron as you note.  Alloys of these two metals (not alloyed with iron) must be in fairly high concentrations which is why our USA nickel coin (25% Ni) isn't picked up by a magnet.  But I'm pretty sure there is at least one Canadian coin which is either pure nickel or very high concentration nickel alloy that is attracted to a magnet.

37 minutes ago, schoolofhardNox said:

Since we are at it.... why not just have a PI side by side with a Magnetometer???

I think tboykin mentioned that above as well.  I can think of *potential* reasons this could be difficult (sensitivity, directional resolution, weight, speed of motion required) but in principle/theory it seems possible.

[klunker]

 

5 minutes ago, Chet said:

What kind of cart or wheelbarrow should we haul this masterpiece on. LOL😄

 Don't know for sure but it should be stout enough to haul the gold out.

I read in an old book that "anything mankind can imagine mankind can do".

[phrunt]

Even people here have come out with a way to detect iron, being magnetic surely makes it something that with time and effort engineers could work out a way to discriminate, maybe not using traditional methods but perhaps there are other ways, like magnetometers although I'm sure that would be flawed in some of the ground here where there is crazy amounts of black sand.  

If the GPZ had GPX 5000 discrimination incorporated that worked because of ZVT coils in a way like the Axiom where you just press a button to check a target I would find it a valuable feature, every feature has limitations and can cause you to miss targets so it's obvious you'd use it if you had to knowing you may miss targets because of it. 

If they can't do it with current technology hopefully they can come up with something new to be able to do it.