Latest Minelab Patent - 11th Feb 2016

[kt315]

Check with metalpopper over on Findmall, maybe he's got it.

What have I become
My sweetest friend
Everyone I know goes away
In the end
And you could have it all
My empire of dirt
I will let you down
I will make you hurt

[Dave J.]

Check with metalpopper over on Findmall, maybe he's got it.

[kt315]

Dave Johnson, i wait a progressive rock from you, not Mozart classic music i am not in. WHERE IS THE CIRCUIT?

[Dave J.]

As you have already explained, the schematic to a CZ would be useless to you.

[kt315]

If you want to build a CZ-5, go ahead and do it. If it's beyond your capability, build something simpler or stick with trying to make an incandescent bulb flashlight work. If you want to know whether or not it's really a PI, there's a guy who posts under the name "metalpopper" on the Findmall technology forum who will probably be happy to help you out on that.

good direction to another american guy. that i do not know. Dave J. i ask from you this schematic
because you are Dave J. - national american hero. the Superman.



in real Dave i do not need in those blank bare texts that you write here. real. my language is the
language of schemotechnics. no another reason i am here.
guys asks me to send DVD-ROM with archive, so do something for the people usefull.
not the sht those american patents you are linking just cause i am not patented minelab troll.
only real schematic gives the real presentation. you know this fact but cover that up.

mersi from beaches of Baltic Sea

[Dave J.]

Dave, people is waiting from you (YOU) the help. schematics and methodics. why (WHY!) you do not want to help?
i ask YOU because you are IN THIS FORUM.
this thread and be not so silent now - YOU HAVE, while i am only simple 315.
http://www.geotech1.com/forums/showt...888#post215888

If you want to build a CZ-5, go ahead and do it. If it's beyond your capability, build something simpler or stick with trying to make an incandescent bulb flashlight work. If you want to know whether or not it's really a PI, there's a guy who posts under the name "metalpopper" on the Findmall technology forum who will probably be happy to help you out on that.

[kt315]

Well, this thread has already been clogged with off-topic stuff, I don't suppose a post on the CZ5 would do any additional harm. What was it you wanted to know?

Dave, people is waiting from you (YOU) the help. schematics and methodics. why (WHY!) you do not want to help?
i ask YOU because you are IN THIS FORUM.
this thread and be not so silent now - YOU HAVE, while i am only simple 315.

http://www.geotech1.com/forums/showthread.php?23098-Anyone-Know-where-to-find-CZ-5-Project&p=215888#post215888

[Dave J.]

Davor is basically correct.

There is a continuum between CZ and BBS. There is not a continuum between BBS and PI, there is an absolutely fundamental difference between those two things which I've explained several times already in this thread.

It is possible to demodulate a PI signal in the frequency domain. That doesn't make it almost a VLF. The fundamental difference between "VLF" and PI, is that in PI metal target signals are received and detected during intervals where the transmit current is not changing. That's what PI is, and what "VLF" (as the term is used in the metal detector industry) isn't-- even in a platform where the machine does both PI and VLF.

[Dave J.]

Davor is basically correct.

There is a continuum between CZ and BBS. There is not a continuum between BBS and PI, there is an absolutely fundamental difference between those two things which I've explained several times already in this thread.

[Davor]

... whereas Dave J's device must filter the RX to admit only selected signals...

... or not. When you consider QSD as an N-path filter, CZ could do just as well without extensive front-end filtering. What those filters do is GB each of the signal paths against the respective QSD phase, and reverse phase/balance the level of the high frequency path. The advantage of filtering is having two pristine pairs of pure R and X quadrature components, but I still vote for a simpler approach.
If there were no front-end filters, you'd have a small portion of a higher frequency X and R included in lower frequency QSD products, but you eliminate those by balancing the higher frequency path.
In effect with BBS signal you can have the exact thing, except frequency paths are processed sequentially. When you have a luxury of GB-ing the quadrature components in a micro, your complete BBS front end becomes a single Tx bridge, a single Rx preamp, and a single QSD. And a micro that does everything else. That's about it.

[kt315]

You look at the BBS/FBS current waveform and see VLF, I say look at the patent and we see TD very similar to PI and nothing like VLF. The only thing certain is that it isn't traditional PI.
---
you will second who says that. after me

[crane]

For those still interested in what BBS/FBS is, here is the voltage & current waveforms:



I've posted this a few times in the past but it doesn't seem to make much of a lasting impression. Look closely at the current waveform... see any 'off' time? Pretty continuous-looking, eh? This is why I posted that 2-frequency sinusoid and asked what is it? and how would you process it?

P.S. -- if you think my Visio art might not be an accurate representation, I've also measured the waveform with a current probe on an oscope. Same thing.

Carl,
Yes you have posted the BBS/FBS current waveform before but it's what we would expect, just as we wouldn't be surprised to see the SD2200 current waveform supplied by Eric in the attached picture.

Anyway, in one form of BBS/FBS BC takes a number of samples at spaced apart times. The first beginning soon after one of the abrupt transitions but after ground eddy currents have decayed (same as PI). One combination is used to cancel the historical component or VRM (same as PI) but where it differs is that he also cancels the reactive signal, which is common to all CW detectors.
Note that he mentions the same rules for the historical component as he does for PI. The VLF phase shift or lag would be explained somewhat differently.

He also points out that the ratio of the reactive (instantaneous) and historical (VRM) signals is independent of frequency up to 100kHz (same as PI) which means that RX is broadband (same as PI) whereas Dave J's device must filter the RX to admit only selected signals. He also points out that Dave's device is FD whereas BBS/FBS is TD.

You look at the BBS/FBS current waveform and see VLF, I say look at the patent and we see TD very similar to PI and nothing like VLF. The only thing certain is that it isn't traditional PI.

[Davor]

Thank you Dave. That's inspiring.
I'm convinced your prediction of multifrequency future was correct. Apart from PI gold machines it is very true for high end machines of today. In the most parts of the world we do not have much use of gold machines anyway.

Given the benefit of time passed, what would you do differently - given the knowledge you have now?

[6666]

Thanks for the story DaveJ

[Dave J.]

Went to work for FRL early Feb 1981, knew nothing about VLF metal detectors. In April I wrote Jim Lewellyn (company president) a memo saying that the future was multifrequency, it would soon do to singlefrequency what VLF did to TR's and what TR's had previously done to BFO's. (With prediction skills like that, it's a good thing I don't play the stock market.) Meanwhile we needed something less ambitious, and that was the 1260-X, the first double derivative pattern "motion discriminator". After we released that in May of '82, I began playing around with multiple frequency. No Internet, nothing available to copy, I had to figure it out on my own. Took a long time, there was lots of other stuff I had to design especially for our industrial line, and we took a long detour into pulse induction (another thing I had to figure out on my own, that's why the Impulse is different from conventional PI). Some prototypes were proof-of-concept that were just for the bench, others were "swingers". The first prototype that resembled what actually went into production was HC-17, "Harmonic Classifier", my 17th multifrequency prototype.

The platform is extremely complex, half the circuitry and most of the tweaker pots could be done in software. Twice during the project I stopped to figure out what it would take to actually do that, and both times I decided that the A/D's and microprocessors then available weren't up to the task, and neither was I (never having coded a microcontroller before). It was going to have to be an all-analog machine. And, iron discrimination was going to have to be reactive, because to do it right using multiple frequency methods would have made the project vastly more complicated than it already was. We introduced it in November 1991 as the CZ-6, a waterproof package without a built-in speaker.

The quest for waterproof came to an end with the waterproof connectors, which field tested fine but didn't hold up in vigorous field use. We had to go back to the old reliable but non-waterproof Switchcraft Slimlines. And, customers wanted a built-in speaker. So first we had the non-waterproof CZ6-A with the Switchcraft retrofit, and then the CZ5 with built-in speaker that survives today as the CZ3-D, which has slightly rearranged target ID categories but is otherwise the same. In 1995 we introduced the scuba-rated CZ-20, later to become the CZ-20 when the manufacturer of the original oil-filled pinpoint switch stopped making it and we had to convert to a piezo switch.