New PI Discriminating patent

[Tinkerer]

Discriminating PI

The big problem at the discrimination on the PI detectors is when the object is very large. If you check carefuly the received signals it is "easy" to disc small objects as coins (see PD3200), but when the object is large then .
All we hope to see this method to work

Could you define what you consider "large"
I tried a 2 liter steel can, is this large enough?

Fe targets have a magnetic reactive component and a resistive component.
Depending on the shape and size of the target, either component may be predominant.
You can easily confirm that with a steel bottle top.

Present the bottle top on edge and the magnetic component is predominant.
Present the bottle top flat to the coil and the resistive component is predominant.

Now take a FE washer or thin disk and repeat.

Now repeat with a washer or disk of copper or any non magnetic metal.

The non magnetic metal has no reactive component and gives a very weak response when presented on edge to the coil.

Tinkerer

[Max]

I appreciate your vast experience with PI detectors.
There are a few PI detectors on the market that claim to be discriminating. I have not had a chance to try any of them.
Did you try one of these detectors that claim to be discriminating?
Do you know what method they use to discriminate FE?
Are there different methods implemented on PI detectors on the market?
Any information would be much appreciated.

Ah, about the bricks, if the detector can differentiate magnetic materials, it can differentiate bricks, but it will still find them.
I test my detector on to a pile of red clay bricks and it works, however I don't know strongly magnetic these bricks are.

Tinkerer

Hi,
I have direct experience with PSII, Lorentz and my homemade GS4... all 3 claimed as "discriminating" PI by respective manifacturers.

About GS4 you do supposed discrimination by considering longer delay for iron...it works in some cases... but it's totally unreliable stuff on e.g. coin or nugget sized objects. So, it doesn't REALLY disc metals... just avoid part of the iron (but very few part) to interfere in your search for valuable things.

The PSII and Lorentz are, instead, pretty similar about indication... but problem is that both fail to disc accurately most , even small, items.

In some cases they can do it really... maybe cause of soil conditions ? In other cases similar objects... e.g. small iron are detected like silver stuff... letting you think the discrimination is so unreliable that you'll never trust it again. Not to talk about e.g. steel objects: real hell for them.

About method: GS4 use delayed large pulse for iron disc but PSII and Lorentz use the exponential decay rate/sampling for disc (at least... I think so) like multiple sampling at strategic intervals... to try to guess what metal caused the variation...

Both ways are unreliable for me: first is too essential/easy... so it's no good at all in real conditions; second one is more complex and give sometimes good results but it's also far from perfection and you would easy leave good stuff or dig iron/steel using one of them in difficault conditions about soil. Also... PSII is not so powerful on smaller coils... disc is even worse with smaller coils.

The problem with bricks is that some give a near to flat magnetic response... and others seems really hot-rocks like volcanic stuff... the last ones are terrible for PIs... where you can compensate them well on VLFs, though not totally and ever, but maybe at 97-98% cases yes. On PIs... simply 90% cases you'll get a false signal from them, no matter if red, orange or gray too!
GS4 is a fairly good example of that: it tunes on the matrix... but every brick piece will trigger it to sound cause of increased alignment of dipoles!

I saw other "disc" PIs too on the field... not used myself but see that all tend to sound when ceramics is there... so inland use it's much like a dream... unless you use hi suspended coils from soil... like 1m frame case...so for depth search only, not shallow.

Kind regards,
Max

[Morgan]

PI

Hi,
you can't discriminate that stuff. They are the pesty stuff for any PI... and I've made so many that I simply KNOW it's impossible disc them out.

So, as rational thought I simply gave up on PI, cause were for me just an enormous vaste of time... with few good results.

Now, about patents and similar stuff... I don't know... maybe some will lead to real MDs in next years... but till now I see nothing about REAL discriminating PI... nor I see any REAL bricks elimiator and the like.

As an example I talk about GS4 : incredible PI, really POWERFUL, deep machine! BUT... it can tune to mineralized soil... but NOT to disc out e.g. bricks!

Simple: it needs constant minerals level to do rejection and so any brick or ceramics make it sing cause it's like an hot-rock there !

And all are the same today... more sensitivity... more bricks you'll dig!

Now... what your idea to eliminate that bricks ??? I cannot see any PI that can do that.

Kind regards,
Max

All Pulse induction SD from Minelab,not detect ceramics or hot rocks,but unfortunetly they can find one single nail very deep...Discrimination is eficient only on the surface.

[Tinkerer]

Discriminating PI

Hi,
I have direct experience with PSII, Lorentz and my homemade GS4... all 3 claimed as "discriminating" PI by respective manifacturers.

About GS4 you do supposed discrimination by considering longer delay for iron...it works in some cases... but it's totally unreliable stuff on e.g. coin or nugget sized objects. So, it doesn't REALLY disc metals... just avoid part of the iron (but very few part) to interfere in your search for valuable things.

The PSII and Lorentz are, instead, pretty similar about indication... but problem is that both fail to disc accurately most , even small, items.

In some cases they can do it really... maybe cause of soil conditions ? In other cases similar objects... e.g. small iron are detected like silver stuff... letting you think the discrimination is so unreliable that you'll never trust it again. Not to talk about e.g. steel objects: real hell for them.

About method: GS4 use delayed large pulse for iron disc but PSII and Lorentz use the exponential decay rate/sampling for disc (at least... I think so) like multiple sampling at strategic intervals... to try to guess what metal caused the variation...

Both ways are unreliable for me: first is too essential/easy... so it's no good at all in real conditions; second one is more complex and give sometimes good results but it's also far from perfection and you would easy leave good stuff or dig iron/steel using one of them in difficault conditions about soil. Also... PSII is not so powerful on smaller coils... disc is even worse with smaller coils.

The problem with bricks is that some give a near to flat magnetic response... and others seems really hot-rocks like volcanic stuff... the last ones are terrible for PIs... where you can compensate them well on VLFs, though not totally and ever, but maybe at 97-98% cases yes. On PIs... simply 90% cases you'll get a false signal from them, no matter if red, orange or gray too!
GS4 is a fairly good example of that: it tunes on the matrix... but every brick piece will trigger it to sound cause of increased alignment of dipoles!

I saw other "disc" PIs too on the field... not used myself but see that all tend to sound when ceramics is there... so inland use it's much like a dream... unless you use hi suspended coils from soil... like 1m frame case...so for depth search only, not shallow.

Kind regards,
Max

Max,
thank you for taking the time to give me detailed description.
From your information I gather that all these detectors use "old PI technology"
In recent times there have been published several patents with new and often very different PI technologies.
When I say "new" like in the case of the Allan Westersten patent #20080150537, mentioned above, it is often an idea that was tried many years ago, like George Payne's patent# 4,110,679 of the year 1977.
For some reason the old patent never made it into commercial production, but using the basic idea and applying modern fast switching transistors, MCU's and DSP, the "old idea" can show its merits.

What can we learn from this?
If one is interested to improve metal detector design, it is worth the time and effort to look at every past idea and patent, analyzing and understanding the basic idea.

Then, off course it needs some inventiveness to come up with one's own ideas of doing the same thing but different.

Here is a question:

Do you know of any PI-MD that uses a concentric IB coil?
I know that DD-IB coils are quite common.
But why not the Concentric IP coils?

When I started experimenting with concentric IB coils, a whole new world of target information appeared.
I am now starting sampling at 3u seconds after switching. Have you ever heard of that with "old PI technology"?

There is a whole new world of MD Technology out there. I find it most exciting.

Tinkerer

[Tinkerer]

Discriminating PI

All Pulse induction SD from Minelab,not detect ceramics or hot rocks,but unfortunetly they can find one single nail very deep...Discrimination is eficient only on the surface.

Morgan,
thank you for the information. It seems then that if we can add true FE discrimination to the SD method, we would have an excellent detector.

Tinkerer

[Max]

Morgan,
thank you for the information. It seems then that if we can add true FE discrimination to the SD method, we would have an excellent detector.

Tinkerer

Hi,
it isn't really: they just compensate some magnetic effects but the bricks I know are detected by SD too, I tested with a friend that has one and they are detected very well by the ML. I will not buy an SD even at 10eur!

It's just a waste of time for me.

About concentric coils: in PI their use is about pinpointing better the target...

let me explain... if you use an 8'' monocoil you'll go already very deep on targets ...easy at 40cm on coin sized stuff in not interfering ground or sand... but it's hell problematic , expecially in inland found the target after a huge mass of soil is removed if it's rusty or same color of ground.

You cannot pinpoint well with monocoils, you just flip an edge of coil over removed soil to find the "line" then seach with eyes and hands... dirty work... and expecially when it's some old bullet you'll recover: compact and small you will not find easy if deformed... you will e.g. confuse it with little stone etc

So pinpointing is due to concentric in some models like AN-PSS12 , minedetector PI technology... cause on mines... you need really pinpointing...

Just this... and no other advantages.

Kind regards,
Max

[Tinkerer]

Discriminating PI

Hi,
it isn't really: they just compensate some magnetic effects but the bricks I know are detected by SD too, I tested with a friend that has one and they are detected very well by the ML. I will not buy an SD even at 10eur!

It's just a waste of time for me.

About concentric coils: in PI their use is about pinpointing better the target...

let me explain... if you use an 8'' monocoil you'll go already very deep on targets ...easy at 40cm on coin sized stuff in not interfering ground or sand... but it's hell problematic , expecially in inland found the target after a huge mass of soil is removed if it's rusty or same color of ground.

You cannot pinpoint well with monocoils, you just flip an edge of coil over removed soil to find the "line" then seach with eyes and hands... dirty work... and expecially when it's some old bullet you'll recover: compact and small you will not find easy if deformed... you will e.g. confuse it with little stone etc

So pinpointing is due to concentric in some models like AN-PSS12 , minedetector PI technology... cause on mines... you need really pinpointing...

Just this... and no other advantages.

Kind regards,
Max

I agree with you about the digging. Pinpointing is very important.
One way of increasing pin-pointing capability, is to increase the PI pulse repetition rate. With a PPS of10,000
and a fast response, using concentric coils, this is much improved.
Tinkerer

[Steve in MS]

I have to agree with Max's opinion on PI's, at least so far. PI's have been around for a long time and no one has really made a good discriminating
and/or ID for ferrous and non-ferrous items. Whites has a new PI with tones that supposed to be better at IDing but I think one would have to fiddle with the settings a good bit to get it to work so so and it has a steep price.
On the other hand, VLf's have proved that they can reliably disc out iron and still get the non-ferrous items, are they perfect in this regard? No, but they do a lot better at doing it and one has to play the odds or dig every single metal item out of the ground which for most of us is unacceptable because of time restraints. Lets face it, it is no fun digging iron all day long, inland detecting requires some form of ID or ability to discriminate between ferrous and non-ferruous items. I have yet to see any PI that would be useful to me because they just are unable to tell the difference between iron and non-ferrous. For that reason, even all metal modes on VLF's have a limited role while detecting, sure they can maybe size up an object or locate a deeper buried object but it is my opinion if there are good objects buried deep, then there will be deeper iron trash items as well.
If there is a PI that can compete with a VLF on ID/ discrimination, someone point me in that direction but I will remain skeptical till I see it for myself and yes, it has to be in a comparable price range.

[Tinkerer]

PI FE discrimination

I have to agree with Max's opinion on PI's, at least so far. PI's have been around for a long time and no one has really made a good discriminating
and/or ID for ferrous and non-ferrous items. Whites has a new PI with tones that supposed to be better at IDing but I think one would have to fiddle with the settings a good bit to get it to work so so and it has a steep price.
On the other hand, VLf's have proved that they can reliably disc out iron and still get the non-ferrous items, are they perfect in this regard? No, but they do a lot better at doing it and one has to play the odds or dig every single metal item out of the ground which for most of us is unacceptable because of time restraints. Lets face it, it is no fun digging iron all day long, inland detecting requires some form of ID or ability to discriminate between ferrous and non-ferruous items. I have yet to see any PI that would be useful to me because they just are unable to tell the difference between iron and non-ferrous. For that reason, even all metal modes on VLF's have a limited role while detecting, sure they can maybe size up an object or locate a deeper buried object but it is my opinion if there are good objects buried deep, then there will be deeper iron trash items as well.
If there is a PI that can compete with a VLF on ID/ discrimination, someone point me in that direction but I will remain skeptical till I see it for myself and yes, it has to be in a comparable price range.

Thank you for your opinion. Everybody is confirming that there is no PI with reliable FE discrimination on the market.
Well, nearly everybody. A few manufacturers do claim that their product discriminates FE. A rather subjective claim.
Now, I have set my mind to design a true discriminating PI. This is why I am looking for all and any information of what the user/operator wishes or expects from such a machine.
My thanks again to all, who have contributed with information and opinions.

So lets consider I have designed and bread-board tested a PI-MD, Hybrid circuit, or something of the kind, that does really differentiate FE, foil and tiny stuff and gives some indication of the size (TC) of the target.

How do I present this information to the operator?
Maybe an audio output that has a center frequency of 500Hz?
Then, a FE target changes the frequency from 500Hz downwards toward 50 Hz?
A non-FE target changes the frequency from 500Hz upwards towards 1000Hz?
The amplitude of the signal changes the amplitude of the audio?
Now, how should I indicate the size of the target? Maybe the duration of the audio signal? this would work in the "motion"or "tracking mode" with a steady sweep speed, but how should I do it when in "pinpoint-mode", when the MD is in non motion mode?

I would welcome all opinions and recommendations on this subject.
I would also very much welcome a circuit of a VCO that does something like that or can be adapted to do it.

Tinkerer

[Tinkerer]

FE discriminating PI

Here is one more patent that claims FE discriminating capability.

Tinkerer

[Max]

Here is one more patent that claims FE discriminating capability.

Tinkerer

Hi,
uhm... now I'll tell you what I think...
there are today so many patents that I wonder why the man was never on Mars (the planet) ever !

There are maybe 100 patents for any real product then really made and sold...

What I'm trying to explain ? Maybe that people patent anything for future rights... and potential revenues but that really few patents then become real devices or machines!? That's the point!

How many patents exist e.g. regarding "phase meters" and methods ??? Maybe 1000 ? Or 10000 ? Who knows ?

But... do you know of 1000 different phase meter devices on the market ???

You're lucky if find a good , single, one !

Cause many of these patents, I tell you now, are just some bla bla ... and nothing more, nothing useful in the real world.

But cause , expecially big companies... but also privates, are ready to spend money for filing them... no problem , the patent office will patent anything for anyone... if some (really minimal) conditions are matched. And first condition is that you pay for the procedure...feeding bureaucracy.

So... if I read that a lot of new patents are made or were made in last years about discriminating PIs... and then I cannot see anything good on the market that REALLY disc as claimed by manifacturers... what matter to me if they have a list of patents long like the route66 ???

I make big laughs of many patents I've read, with very few exceptions, cause most are plain BS and/or just pompous words that never will become facts.

That's like beliving at lawyers... and to some magnificent harangue... missing that maybe the charged is, out of any dubt, guilty!

So... people that belive in rethorics... could save who is on fault from the electric chair and maybe giving some conviction to innocent dudes... with the only fault they have no patent agency ...ops...sorry... good lawyers to take care of rethorics and other details!

Now... I think it's really clear: if there are those patents ...why they aren't employed to realize real discriminating PI MDs ?

I tell you: cause are plain rethorics too and they...the patent owners... discovered the hot water, once again! The PI technology is the same of 20, maybe 30 years ago... today!

We have plenty of microprocessors and adcs...all a new universe of amplifiers etc etc lock-in toys and what else ? But we haven't A SINGLE ONE (REALLY) DISCRIMINATING PI.

Just my thoughts...

Kind regards,
Max