Latest Minelab Patent - 11th Feb 2016

[Qiaozhi]

It's easy to think that mixing the two technologies in the same machine would be a good idea. I've done it because the boss thought it was a good idea even though I told him it wasn't, and in the end the distributors told him Dave was right. And throwing that mistake out is what made it possible to get the CZ. Nowadays it costs far, far more to develop a new high end platform than it did in the 1980's, and the problem is still identifying what problem a hybrid PI-VLF is supposedly going to solve that makes it worth spending a million bucks to turn it into a product.

Carl was right: "couldn't figure out what the whole thing would be good for".

Burning the midnight oil (actually 2:38 am in El Paso) ??

[Dave J.]

"...and the problem is still identifying what problem a hybrid PI-VLF is supposedly going to solve that makes it worth spending a million bucks to turn it into a product..."

Putting it that way... well, it is hard to imagine any of the existing models that will meet such criteria!
When business takes over than all the enthusiasm goes down the drain.
As for the Carl... i believe he is just rocking the cage here! As usual.

As a hobbyist, or even in technology development in a business, you do gobs of "neat stuff" without having to first find a multimillion dollar market for it. In the case of the hybrid that we scrapped back in the late 1980's, if we'd gone into production with it, there would have been customers who thought it was a great product. It did neat stuff that nothing else did, and was even easy to use. It would have developed a cult following.

The problem was, that we needed to devote our limited resources to come up with a product that we could sell to a lot more customers than would ever have bought that hybrid machine. Business is not a bad thing, and done right it promotes enthusiasm. Developing that hybrid machine was a lot of fun even though it was a bad idea from a business perspective. Developing the CZ was fun, and we've been selling 'em for 25 years now. I'm still having fun developing metal detectors, and because it's a business the boss even pays me to do it.

[moodz]

... back on topic ... I have obtained the exclusive TC waveform of the target that this patent was designed for ...

It has a decay period of about 5 years and peak target response was about 3 years ago.

[Qiaozhi]

... back on topic ... I have obtained the exclusive TC waveform of the target that this patent was designed for ...

It has a decay period of about 5 years and peak target response was about 3 years ago.

Very amusing.

Presumably that's the share price chart for Codan Limited.
Apparently (for 2016) Minelab revenue increased 70% over the first half with release of the GPZ 7000® gold detector and the GO-FIND® metal detector.

[moodz]

...well on a serious note ( depending on the company ) .... there has to be a semi regular release of "suitably complex" patents to keep the investors interested if nothing else will.
This may be one of those patents on a journey to somewhere ... maybe a product or a stocking filler ( pun intended )

[crane]

Excuse me but the concept of "saline" is mentioned casually and only ONCE in the patent:

[0050]....The discrimination method offered by the present invention is insensitive to both resistive and reactive signal components from the soil, which may] also include a component due to a substantially uniform conducting half-space (such as a saline] soil)."

You can write "my invention does this" or whatever your fantasy decides, however, in order to patent it you must DISCLOSE how it's done. This paragraph provides no disclosure, therefore it's a mere DESIDERATA (expression of a wish) with no technical substance to it.



Methods of GB that leave the TC untouched are known long ago, see paragraph 6.5 on page 50 of the following publication:

UXO TARGET DETECTION AND DISCRIMINATION WITH ELECTROMAGNETIC DIFFERENTIAL ILLUMINATION

Therefore the sequence is an obvous combination.

I read that paper a few years ago and I won't be reading it again. It, like most UXO papers, is almost useless and it certainly doesn't leave the target TC untouched. Why would anyone use crude curve fitting to cancel VRM ground when other methods work better. They mention ML's early GB solution and even quote Bruce Candy's math. Skip to the end and they admit they didn't solve any problems or come up with anything new, they just simply learnt what most people already know.

[crane]

If KT is confused and not just yanking chains, then his confusion is understandable. You can use virtually identical transmit circuits for either PI or VLF. Some time ago for funsies, I decided to design a single transmitter circuit that could transmit a resonated sinusoidal, a traditional unipolar PI, a bipolar PI, a triangle current (e.g. BBS/FBS), an Impulse-style variable-slope pulse, a half-sine, or a truncated half-sine. And, to make it more interesting, support 2 frequencies for any of them. All user-selectable as it was running. It was a helluva challenge but I was successful. Using an IB coil feeding a generic quadrature demod system, I could have then processed the RX any way I wanted. But I couldn't figure out what the whole thing would be good for, so I stopped there.

Crane, technically all detectors process the RX signals in the time domain. Any traditional VLF could use smaller time slices as BBS/FBS does and still work, and any traditional VLF could use a BBS-style triangle wave TX current and still work, as the CZ proves. And, if you did BBS with just one frequency instead of 2, you would say "that's obviously VLF, not PI."

But... there are not two frequencies with BBS/FBS, they use multi-period pulses.
VLF GB mixes R with X whereas BBS/FBS subtracts a late sample from an early sample, same as PI.
The VLF sample window is one half cycle wide or less, a number of smaller slices do nothing in VLF except give very poor S/N. See early VLFs such as Compass that demodulate roughly 20% of one cycle and toss the rest out.

[Teleno]

I read that paper a few years ago and I won't be reading it again. It, like most UXO papers, is almost useless and it certainly doesn't leave the target TC untouched. Why would anyone use crude curve fitting to cancel VRM ground when other methods work better. They mention ML's early GB solution and even quote Bruce Candy's math. Skip to the end and they admit they didn't solve any problems or come up with anything new, they just simply learnt what most people already know.

Well, ML didn't come up with anything new either, since modeling the signal by two time constants - and doing so by crude curve fitting!!! see [0052], [0052] and 0071] - for classification purposes is known ages ago. Whether you classify a given pair of taus as ground, saline, target X or smurf droppings is immaterial because the method is exactly the same.

Quote:

[0084] Although the brute-force search performs the best...

wow!

[daverave]

Hi Dave J. Did you get good depth in discrimination ID and knock out iron ???? my friend did a proto type pulse ID machine some years ago and now he is going to develop it further for himself cause where we live the gold items are now very deep and lots of iron masking good signals...myself im going to experiment with magnometers as a way of rejecting iron......i feel its best to reject iron more than having full ID.

[Davor]

But... there are not two frequencies with BBS/FBS, they use multi-period pulses.
VLF GB mixes R with X whereas BBS/FBS subtracts a late sample from an early sample, same as PI.
The VLF sample window is one half cycle wide or less, a number of smaller slices do nothing in VLF except give very poor S/N. See early VLFs such as Compass that demodulate roughly 20% of one cycle and toss the rest out.

I'd give you my 5 cents on this, but I'm afraid they'll end up in a Candy jar.

As for demodulating shorter angles of a periodic signal, the advantage is a better (!) conversion gain than a 50% angle (~1/π=-9.9dB).

[Dave J.]

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

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.

[ivconic]

As a hobbyist, or even in technology development in a business, you do gobs of "neat stuff" without having to first find a multimillion dollar market for it. In the case of the hybrid that we scrapped back in the late 1980's, if we'd gone into production with it, there would have been customers who thought it was a great product. It did neat stuff that nothing else did, and was even easy to use. It would have developed a cult following.

The problem was, that we needed to devote our limited resources to come up with a product that we could sell to a lot more customers than would ever have bought that hybrid machine. Business is not a bad thing, and done right it promotes enthusiasm. Developing that hybrid machine was a lot of fun even though it was a bad idea from a business perspective. Developing the CZ was fun, and we've been selling 'em for 25 years now. I'm still having fun developing metal detectors, and because it's a business the boss even pays me to do it.

"...we scrapped back in the late 1980's...It did neat stuff that nothing else did, and was even easy to use. It would have developed a cult following..."

What's stopping you to share it here with us, now, 30 years after?
Don't rock our cage here as Carl do, for nothing! Maaannn! Duuuude!
BTW this reminds me on Minelab FT16000 from 1990.
Once i asked ML for help on servicing it.
I got response in manner: " Sorry we can't help you, technology involved in it is in further developing and use ever since." !?!?!?!? Ooooooahaahahahahahahahah!
Still have stomach for reading their "fresh" patents?
So if you answer me in the same manner... duuuude!
Bring it on! 30 years has passed!

"...Developing the CZ was fun, and we've been selling 'em for 25 years now..."

CZ is alright. One of the most respectful models on my list.

"...I'm still having fun developing metal detectors, and because it's a business the boss even pays me to do it..."

You are very lucky man. Doing what you enjoy to do and being payed for that!
What's better than that? Being a boss...?

[green]

You are very lucky man. Doing what you enjoy to do and being payed for that!
What's better than that? Being a boss...?

Only if you like being the boss.

[ivconic]

You are very lucky man. Doing what you enjoy to do and being payed for that!
What's better than that? Being a boss...?

Only if you like being the boss.

I was hoping to see answer like:
"Being a boss...?" - "Being with boss's wife instead is better!"

[Dave J.]

"...we scrapped back in the late 1980's...It did neat stuff that nothing else did, and was even easy to use. It would have developed a cult following..."

What's stopping you to share it here with us, now, 30 years after?
Don't rock our cage here as Carl do, for nothing! Maaannn! Duuuude!
BTW this reminds me on Minelab FT16000 from 1990.

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.