The Discriminating (to iron) Pulse Induction. - Fantasy?

[Ringzapper]

I have often wondered why no one has designed better iron id methods on pulse induction detectors. I see big technological advances in things like plasma TVs, Cell Phones , Computers etc etc. Why after all these years are pulse induction detectors doing no better at iron id than they did 30+ years ago. I think it would be possible to build a PI machine that uses a second system using VLF technology to id the iron. Some people are using pulse induction detectors to locate a target, they mark the spot with a golf tee or spray paint then they use a second machine usually a VLF to check if it's iron.
I think manufacturers are being lazy here in not doing more to get better iron identification . I think it is entirely possible to build some sort of hybrid PULSE / VLF . The future in recovering the deepest coins missed by vlf's over say the last 30- 40 years is in my opinion pulse induction with discriminating ability. I heard a dealer say the latest pulse machines with so called iron id are useless in giving good iron identification.

 

[landman]

I believe they have. It's called the DRS GroundExper. Bought one. It's a digital pulse. I can knock out iron easily.
Check it out.

 

[metalpopper]

The pulse machine with excellent iron discrim are already marketed.....they're the MINELABs.......The SOVs..EXPLORERS....Etracs CTX 3030...

Multi Pulse train...Induction balanced coils......3 channel analysis....and superior signal analysis.......All that you are 'searching' for technologically....

Even Eric Foster's relatively primitive PI have models with an IRON channel and a GOLD channel, selectively switched mixing to achieve various degrees of disc...

The Minelab's CTX 3030 is is the present state-of-the-art leader.......

The magic of applied mathematics and deep understanding of how materials interact with varying magnetic flux, is what physicist Bruce Candy is famous for.

There are two principle modes of enjoying our hobby....doing it for simple pleasure of finding, by chance; ....and also by learning how it 'works', and hunting

purposefully......Matt.

 

[markg]

So the Etrac and CTX are PI machines?

 

[metalpopper]

Yes, Dave.....as is also for a further example, are the Whites V3's, with the added benefit of 3 conventional single frequency modes.

MINELABs use the multi pulse widths convention to allow their claim of Broad-band detecting...1.5 Khz to 100 Khz.

That's theoretically correct with respect to the harmonics involved;... but practically, it must be understood that the

actual power spectrum has to be shared in diminishing proportions related to the harmonic number..

The consequences are, that thin-section-low-conductors can be harder to find at even shallow depths.

Despite that, the Minelabs are my favourite wet-sand machines, especially for deep silver/copper,

and moderate to thick gold rings etc.

Love my Whites to......so educational, and adaptable,to suit your personal modes of searching.

The biggest problem faced by the designer, is to practically manufacture an efficient search-coil that will perform

efficiently over a broad frequency range......

Just a few facets of the many aspects involved.....matt



o

 

[Dave J.]

The Minelab BBS machines are not PI's, nor is the White's V3. Both are multifrequency IB VLF's, although that's just all they have in common (they're very different both externally and underneath the hood). .

I built a stone-axe simple PI back about 1985 that weighed a hair over 2 pounds, ran off a zinc-carbon 9 volt battery, and knocked out everything below zinc (including iron), fully static operation like an old-time VLF-TR discriminator. Unlike VLF-TR, mineralization didn't bother it. Real sweetheart of a machine for snagging high-conductivity coins amid trash. Unfortunately it would only hit coins down to about 5-6 inches and while that ain't bad in nasty mineralization, it just ain't enough in regular dirt.

 

[metalpopper]

The Minelab BBS machines are not PI's, nor is the White's V3. Both are multifrequency IB VLF's, although that's just all they have in common (they're very different both externally and underneath the hood). .

.

Dave..re-part of your post..quoted above:.

.'.A rose is still a rose, by any other name'[/cente

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~​

Hello Dave, thank you for your erroneous perceptions regarding pulse-induction.
You are not alone in miss-understanding the subject matter.
Your use of advertising writer’s ‘terminology’, is a typical substitute for a
lack of real understanding of the correct terminology of what I was endeavouring
to convey, to the writer of the original post.
ALL of the detectors which I mentioned... TRANSMIT PULSES.....and as I clearly mentioned,
the Whites also has a SINE-WAVE, single frequency alternative modus-operendi.
--------------------------------
PULSE INDUCTION.
In simple, factual terms, it classifies the method of detecting whereby a detector emits
PULSES of energy,
which if INDUCED in a target material, (by the process of electro magnetic INDUCTION),
causes a time-delayed modification of the original transmitted waveform.

A PI detector then senses this interactivity by sampling the 'back-emf' of the modified TX pulse,
as it decays after transmission.

A typical PI ‘receiver’ samples the delayed response, and processes it in a manner technically classed as 'Time-domain'. (Integrating the RX signal, and sampling at various delayed times, with reference to the TX pulse timing.
++++++++++++++++++++++++
All the detectors I mentioned follow those basic methods.
Any manufacturer’s/designer’s embellishments are what they patent;
but the patent classification is fundamental.....PI
The fact that a single loop, or ANY other configuration of loop(s) may be employed to
sense the modifying effects by interactive induction of the TX pulse, DOES NOT alter
the fact that the method use....ie PULSE INDUCTION.......matt

>>>>>>>>>><<<<<<<<<<<<<<​

p.s. You mentioned that you have in the 1980's built a PI from a kit source, or someone else's design.

That doesn't necessarily mean you understand the principles of pulse induction, otherwise you
wouldn't be posting your misconceptions about what detectors use pulse TX methods.

Perhaps you may care to better explain/depict for forum readers, in diagrammatic form,
how a conventional VLF detector transmits, compared to a PI?

That would surely prove your point...???????...respectfully awaiting your reply​

 

[Reg]

Matt,

You obviously do not know who Dave J. is. When you have designed and built as many detectors for major companies as Dave has, then you can discuss the issue at hand. Ever heard of Fisher, White's, First Texas, Tesoro? Well, Dave has designed detectors for those companies, many of which are still active today. When you hear the names, White's MXT, GMT, Tesoro's LST, and a whole lot of First Texas" designs today and most of the original Fisher's motion detectors, think of Dave J. Plus the guy has several patents to his name.

How many metal detectors have you designed?? How many patents do you have to your name? Insulting Dave J. really is not the thing to do.

Just for the record, I agree with Dave, the detectors you mentioned are not PI's as we know them.

Reg

 

[Frank-S]

Most VLF and PI when detecting iron non-ferrous go negative, gold ferrous go + positive.
if you experiment with a zer-O center meter , you might come up with a iron ID.

 

[trojdor]

Matt,

Oh, my...

You just lost all credibility by not recognizing who you were responding to.
To put it simply: Dave has forgotten more about metal detector design, operation and physics that you will ever learn in your entire life.

Trying to arrogantly and cluelessly school the master...in a public forum...oh, my.

And that pulse machine he was talking about...major breakthrough of his own design. Google the CodFisher Pulse unit for the whole story.

I would not want to be in your place...sorry, dude.

 

[lytle78]

My post was redundant - I Have deleted it.

 

[trojdor]

My post was redundant - I Have deleted it.

I don't know...I kind of liked it.

 

[lytle78]

Reg's article is linked in the thread about the deepest PI detector. Here it is again.

http://web.archive.org/web/20090201183352/http://www.nuggetshooter.com/articles/UnderstandingPIdetector.html

Dave's post was so low-key and generally informative, that I'm surprised anyone would climb onto such a high horse in response.

Some of my most painful injuries have come from striking the ground when falling from a "high horse.".

 

[metalpopper]

Matt,

You obviously do not know who Dave J. is. When you have designed and built as many detectors for major companies as Dave has, then you can discuss the issue at hand. Ever heard of Fisher, White's, First Texas, Tesoro? Well, Dave has designed detectors for those companies, many of which are still active today. When you hear the names, White's MXT, GMT, Tesoro's LST, and a whole lot of First Texas" designs today and most of the original Fisher's motion detectors, think of Dave J. Plus the guy has several patents to his name.

How many metal detectors have you designed?? How many patents do you have to your name?

Insulting Dave J. really is not the thing to do.

Just for the record, I agree with Dave, the detectors you mentioned are not PI's as we know them.

Reg

_________________________________-​

Thanks Reg for your post; (and others), and yes I'm familiar with Dave’s involvement with the hobby. That is why I was ‘surprised’ by Dave’s reply, for I would have expected a more pragmatic contribution than the bland post which simply regurgitated the ‘cover-all’ non specific classification’ of VLF etc., in his curt dismissal of my assertions on what constitutes a Pulse Induction detector.

Such phraseology is more at home in advertising hype prevalent in the hobby, than a meaningful, explanation of his own reasoning of why HE thinks the detectors I mentioned, do not use Pulse Induction as the primary driving force in their design; (Hence my classifying them as P.I.)

The term VLF is a generalisation, referring to sine wave driven detectors. (In the low KHz range.)

P.I. refers to any class of detectors using the alternative drive method of a RECTANGULAR PULSE or PULSES.
(A single pulse generates limited ODD harmonics of diminishing useful amplitudes, and a ‘MULTI-PERIOD PULSE train, is used to extend the range of ODD harmonics)
Repetition of any specific-width of pulses within that train of pulses intensifies the frequency spectrum generated; as typified in MINELAB E-tracs etc., to enhance their sensitivity to targets of thin section and/or low conductivity.
The detectors models I quoted are functionally Pulse Induction driven, as distinct from ‘VLF’ single frequency, sine-wave driven types. (WHITES V3 series uses offers PI and VLF mode selection.)

^^^^^^^^^^^^^^^^^^

Well gentleman, those comments are simply a brief expansion of my original, posted statements.
I still can’t fathom out why Dave would disagree, especially because he has in the past, gone on
record demonstrating his concessions to PI / multi-frequency development attributed to MINELAB
and WHITES, as distinct from ‘VLF single-frequency technology.
(I have several documents from the past related to Dave’s observations etc., on my hard drives.)

Insulting Dave?.... “Poking a sleeping dog” would be more relevant; for as he once stated..’Read a lot of forum stuff, but rarely reply’...
I think he’s made of tougher stuff than you protagonists give him credit for!

So, I’m just hope that Dave will offer an explanation as to why he bluntly asserts that I am wrong.

xxxxxxxxxxxxxx​

As for the non-technical contributions from those who have re-acted in a manner which they claim I am guilty of...

..then you too suffer the same short-comings as attributed to me.

Gentlemen, ”Goodnight.” Matt.

 

[lytle78]

Oh Boy - we've got a live one.

matt.

What have you designed and built?

What have you found?

Why should we care about your nitpicking definitions arguement which you are trying to pick with Dave J.

If you understand so much, why don't you CREATE something instead of wasting the time of someone who has?

I notice you use a lot of important sounding words - words mean little, show us some results.

 

[Carl-NC]

Hi Matt,

Dave is 100% correct, BBS/FBS and White's V3 are not PI detectors. A VLF detector does not have to have a sinusoidal transmit signal, it could use a triangle wave for example. In fact, I could take most any VLF detector and convert the transmitter from sinusoid to triangle wave, everything else the same, and it would still work.Sinusoids dominate simply because it makes a more fuel-efficient transmitter.

BBS/FBS and White's V3 use triangle wave transmitters with demod processing much like a normal VLF (such as generating resistive & reactive demod signals, which decay-based PI's don't do). BBS/FBS (from Sovereign all the way to CTX, all identical) sequentially transmits 3.125kHz and 25kHz triangle waves. V3 simultaneously transmits 2.5/7.5/22.5kHz in a rather complex multi-triangle waveform, and in single frequency modes transmits a simple triangle wave. As a bonus example, the Fisher CZ's transmit a single 5kHz triangle wave, and run the demods at the fundamental and 3rd harmonic, still using VLF techniques. None of these detectors generate current pulses.

- Carl

 

[lytle78]

Thanks Carl.

Here I went and got all excited, accused poor Matt of being a time waster, when the facts he had asked for were coming just down the road. Lesson learned.

Matt, Carl Moreland is the former Engineering Division Manager of Whites Electronics and currently is the Engineering Manager at First Texas Products (fisher, Teknetics and Bounty Hunter).

Matt, in a way, I owe you an apology. I have long been confused by Minelab's technobabble which you set forth at length, and now it is partially dissipated, thanks to Carl.

But now it's goodnight to all.

P.S. If Matt or anybody else wants a good technical overview of Metal Detectors, I can recommend George Overton and Carl Moreland's "Inside the Metal Detector".

http://www.geotech1.com/forums/content.php?125-inside-the-metal-detector

 

[Dave J.]

You're giving Matt too much credit, Rick.

The mathematical-sounding explanations he was throwing around are just his fantasy, they fill the bill for bogus and bull. He's just blusterbluffin' ya (the tone of the post was a dead giveaway on that one).

http://www.dspguide.com/ch13/4.htm

Well, I'm gettin' kinda old, I try not to devote more than 1% of my time arguing with, well, y'know........... the kind of people that the Right Honorable Samuel Clemens recommended staying mark twain away from. But if Matt wants a learning experience the link above is a great place for him to start. No need to listen to people like myself and Carl who have actually designed and built stuff that works.

--Dave J.

 

[robby_h]

Hi Matt,

Quote: "PULSE INDUCTION.
In simple, factual terms, it classifies the method of detecting whereby a detector emits PULSES of energy, which if INDUCED in a target material, (by the process of electro magnetic INDUCTION), causes a time-delayed modification of the original transmitted waveform".

This doesn't apply to conventional pulse induction because the receive signal is sampled after transmission has ceased.

There are two main schools here, one advocates a pulse where current rises rapidly and then "flat tops" for most of the pulse. If the target's TC is very short compared to the pulse length then the target is just sitting in a static filed at switch-off so your PI transmitted waveform doesn't play a part in generating the target signal. In this case the pulse in "pulse induction" is the magnetic step at switch-off.

"A PI detector then senses this interactivity by sampling the 'back-emf' of the modified TX pulse, as it decays after transmission".

A PI detector doesn't sample the "back emf of the modified tx pulse", it waits until after the spike has fully decayed and then looks for a signal received from the environment. The back emf spike and the receive signal are two entirely separate events and if you sample too early your measurements will be contaminated by variations in the spike's width or settling time, which is the result of minerals or the target altering the coil's properties, it isn't a received signal.

CW including VLF operate in the frequency domain whereas PI, BBS and FBS are all time domain but the latter two receive during transmission so aren't traditional PI detectors.

 

[Dave J.]

Yeah, Rob, but wait till Bruce explains to Hapless Matt how the GPZ7000 works! Poor guy's gonna be so bewildered that he'll have to ask the security guard to help him find the front door! But when Matt picks up on the part about energy recovery, he'll probably spend the next 20 years trying to convert a metal detector into a perpetual motion machine.

So on second thought, Matt's much better off not coming up with a million dollars and paying Bruce Candy for privately tutored semester course on how metal detectors work.

[And who knew that a metal detector technology forum could get as tinfoil hat ridiculous as an LRL forum??!!]

--Dave J.