Latest Minelab Patent - 11th Feb 2016

[ivconic]

As for the person from non-English spoken population; the term "Pulse Induction" can be understood as induction which occurs after the pulse was "transmitted".
So it's not continuous signal; it's the pulse.
This is not necessary correct lately, as Dave explained much better than i would ever be able to explain.
And this negates my previous claim about how is not important what you tx but is important how you rx it back.
Well, i was partially wrong and Dave was not completely right.
KT's confusion (if real) was mostly due similarities between tx's on few different designs. I was pointing on that particular case and not generally.
In that particular case the difference was in how you rx back and analyze induced signal.
In generally speaking... i think nowdays is not possible to speak generally any more.
Because PI techniques evolved in several different directions and as time goes on it will be increasingly difficult to make a clear separation and distinction among those and be able to clearly identify and in what category it belongs.
But in one thing Dave is right for sure; "...Once you've actually designed both kinds, it is simply impossible to confuse PI with VLF, even in a machine which does both things simultaneously...."

[ivconic]

Simply pointless to go to the trouble of dredging the schematics out of the files and posting them. The technology is described in the CZ/Impulse patent, and the Impulse schematic is posted on this forum. Anyone who wants a discriminating PI who is capable of actually building one that works, will want to do it their own way anyhow, nobody in their right mind would want to build the one which looked interesting late 1980's but would be met with universal derision now. Had it become a product, someone might at least want a schematic for troubleshooting their stone age unit, but it never became a product.

The CZ/Impulse patent that explains so clearly the issues involved in both technologies, it's become obvious during the lat 48 hours that some of our most prolifically posting forum denizens haven't even bothered to read it; or if they have read it, it made no sense to them. These are the same people who would build and get working the machine we gladly scrapped nearly 30 years ago? I don't think so! As far as I know, nobody has even replicated or adapted the Impulse transmitter & front end, even though it's arguably the easiest of all PI designs to actually build and get working properly.

Where exactly is that patent and that schematic?
Seems somehow i missed them here on forum?
Or i forgot.
For long time i was not interested in PI designs at all (not that i changed my mind now) and that's probably why i don't know what are you talking about...
I would like to see them.

[Dave J.]

In this thread, several posts have listed the patent number, and I linked the local schematic. In the last 48 hours we've darn near flogged it to death.

[ivconic]

In this thread, several posts have listed the patent number, and I linked the local schematic. In the last 48 hours we've darn near flogged it to death.

Sorry!
I was focused on mockery than!
Right now i founded US4868504 and i am reading it.
I also downloaded US4628265 and US4514692.

[ivconic]

Ok i partially got it!
Patent US4868504 actually explains fisherpuls.pdf schematic!
But all the time i am confused with year " '91 " and "CZ" and that's why i am having troubles to locate proper documents here!
Year noted on patent is "1989" and not " '91" and there is no "CZ" word mentioned anywhere in what i am looking right now!?
Ok... that's not important for what i want to ask here.
I am looking at schematic and i have few points to mention/ask.
SSM2220 dual matched transistor? Is it crucial? Can't it be substituted successfully with common parts?
It's not easy (if not impossible) to obtain it nowdays in local shops.
This:

"... As far as I know, nobody has even replicated or adapted the Impulse transmitter & front end, even though it's arguably the easiest of all PI designs to actually build and get working properly..."

is probably true, but maybe just because of the reason that some components are not easy obtainable, obsolete, discontinued?
With little help on this with hints; i might be interested to draw my own pcb version for it and diy it eventually. Whole process i can present here on forum in dedicated and separate topic.

[Dave J.]

The patent says nothing about the CZ or the Impulse specifically, because those are products that were released after the patent was filed.

Building circuits is a job for people who know how to do such things, I don't have the time to kibitz someone on a project to help them get it working. In the case of the Impulse, I've built and tested a whole slew of different preamps and most of them worked just fine. Same with AC amp chains and demodulators: one early PI I built ran the output of the preamp through a bandpass filter and then the signal was demodulated more or less as though it had been a VLF. It didn't see magnetite because the preamp was gated.

[ivconic]

The patent says nothing about the CZ or the Impulse specifically, because those are products that were released after the patent was filed.

Building circuits is a job for people who know how to do such things, I don't have the time to kibitz someone on a project to help them get it working. In the case of the Impulse, I've built and tested a whole slew of different preamps and most of them worked just fine. Same with AC amp chains and demodulators: one early PI I built ran the output of the preamp through a bandpass filter and then the signal was demodulated more or less as though it had been a VLF. It didn't see magnetite because the preamp was gated.

It's alright. You have an inviolable right to your attitude and in your decisions.
Nobody should argue on that.
Keep cool.

[Carl-NC]

Carl; that's interesting!
Have you done it based on MCU or completely analogue? Is it available to be seen in public?

The TX circuit was analog, although you'd want to clock it & control it with a micro. Some of it I figured out before White's, some during. So even if I had the design, I couldn't share it, and I don't have it. I'd have to start all over again. Fundamentally, it is based on a full H-bridge. A couple of times I've thrown out some comments on these forums that were hints on how to design a hybrid transmitter, but no one seems to have bitten on it.

But... there are not two frequencies with BBS/FBS, they use multi-period pulses.

As David suggests, look at the TX current, not voltage. Then it's obvious.

[ivconic]

The TX circuit was analog, although you'd want to clock it & control it with a micro. Some of it I figured out before White's, some during. So even if I had the design, I couldn't share it, and I don't have it. I'd have to start all over again. Fundamentally, it is based on a full H-bridge. A couple of times I've thrown out some comments on these forums that were hints on how to design a hybrid transmitter, but no one seems to have bitten on it.
As David suggests, look at the TX current, not voltage. Then it's obvious.

I see. Thanks for clarification.

[Carl-NC]

A couple of times I've thrown out some comments on these forums that were hints on how to design a hybrid transmitter, but no one seems to have bitten on it.

Here's one of those hints, expanded: The Impulse transmitter design is a prime starting point for anyone wanting to design a hybrid VLF/PI. It's where I started. Build it, and play around with caps & diodes and see what happens.

[Davor]

It is far cheaper and faster doing such things in Spice. It even allows you to do some completely crazy things with idealised "components", and if you like the outcome, you find a way to make it real.

[ivconic]

Here's one of those hints, expanded: The Impulse transmitter design is a prime starting point for anyone wanting to design a hybrid VLF/PI. It's where I started. Build it, and play around with caps & diodes and see what happens.

Obviously you are knowing what are you talking about.
But than again; insisting on TX as "prime starting point..." will wake up KT and put additional oil on his recent fire!
A cage rocker... as i said!



How can i disagree?

[Carl-NC]

It is far cheaper and faster doing such things in Spice. It even allows you to do some completely crazy things with idealised "components", and if you like the outcome, you find a way to make it real.

That's exactly what I did

[Orbit]

Whether I understood given this topic ?

[crane]

Multiperiod pulses is Minelab's PI's, for the purpose of fitting the magnetic viscosity curve better. The BBS waveform has been published a few times (I assume even here) and some folks (Carl included) have looked at it directly. It is indisputably a sequential multiple frequency waveform with continuously varying transmit current and as Carl said, if you pick a single frequency section of that waveform it looks just like the CZ waveform. No matter what you do in the receiver, you can't turn it into a PI.

The essential difference between PI and the pile of stuff that by metal detector industry custom we call "VLF", is that PI detects targets during time intervals during which the transmit current (and therefore transmit field) is not changing. VLF's don't do it, PI's do. And, that difference is essential: it's what gives PI's the natural born ability to ignore magnetite and induction imbalance (i.e. reactive signals), whereas in VLF's these same reactive signals are the biggest single engineering problem that has to be adequately overcome before you do anything else.

Once you've actually designed both kinds, it is simply impossible to confuse PI with VLF, even in a machine which does both things simultaneously.

We're going around in circles here. I'm not saying BBS/FBS is PI, I'm saying it is more closely related to PI than it is to VLF.

Yes, multiperiod pulse is for Minelab's PI but they apply the same to BBS/FBS. The patent description even says so, ie, Discriminating Time Domain Conducting Metal Detector Utilising Multi-Period Rectangular Transmitted Pulses. There are no two frequencies just as there are no two frequencies in their MPS PI detectors. You can't possibly come away thinking VLF after reading the patent!! The processing is entirely different!

One other thing, a few people here think that a PI ignores all magnetite. It might in the USA and some other parts of the world but the stuff we have here on our goldfields can give a very high amplitude VRM response on a PI and this is before its structure is altered in bush fires. This stuff gives two signals, the reactive, which PI ignores (well almost!!), and VRM which requires a GB circuit.