GPZ 7000 ZVT Technical & Audio Questions

[AussieMatt]

Was wondering if anyone had any technical info on the GPZ7000.

Read on an Aussie forum that the ZVT technology is in fact Pulse Induction. It is my belief from what I have read elsewhere & what Minelab are saying that it isn't Pulse Induction but a completely new, standalone technology at it's early stages with more improvement to come? Does anyone know if ZVT is technically a variation of Pulse Induction or in fact totally new? 

 

Also the audio output of the GPZ7000 - in the same thread it is suggested "listening to the sounds of targets being located makes it obvious that the GPZ is basically a PI detector". It was my belief that detector tones can be set by the technician over a range of "sounds" & that Minelab set theirs at the distinctive warble/tone of previous machines. The sound wouldn't have anything to do with the "type" of detection technology used? Or does it? 

 

Anyhow it doesn't really concern me either way but I am watching with interest how things unfold now it's getting out there with more users. A very interesting machine but the SDC will have to do me for now.

[Steve Herschbach]

Audio in a VLF detector while in discrimination mode can very much be a creation of the engineer. The signal is intercepted, interpreted, and delivered to the operator. The sound that is delivered can be anything the engineer wants, including the words "you have found a dime".

When a VLF is in pure threshold based all metal mode you are listening directly to the detector with minimum filtering introduced. You hear nuances of the ground signal itself and other audio details.

A PI is normally a true all metal type unit that delivers the signal with minimal processing. The GPX detectors are probably the most processed models. The SDC offers a livelier audio. The GPZ is sort of between the two.

Long answer to say yes, you can get a bit of an idea what is going on from the audio. The Minelab PI dual tone response is an artifact produced by the current ground balance setting and the relation of the target to that setting.

The thing here is the GPZ really is new. It is a hybrid; it is not pure PI nor pure continuous wave (VLF) but has attributes of both.

From http://www.whiteselectronics.com/the-hobby/knowledge-base/field-reports/how-metal-detectors-work

"a typical PI search loop contains a single coil of wire which serves as both the transmit and receive coil. The transmitter operates in a manner similar to an automobile ignition system. Each time a pulse of current is switched into the transmit coil it generates a magnetic field. As the current pulse shuts off, the magnetic field around the coil suddenly collapses. When this happens, a voltage spike of a high intensity and opposite polarity appears across the coil. This voltage spike is called a counter electromotive force, or counter emf. In an automobile it is the high voltage that fires the spark plug. The spike is much lower in intensity in a PI metal detector, usually about 100 to 300 volts in peak amplitude. It is very narrow in duration, usually less than 30 millionths of a second. In a PI metal detector it is call the reflected pulse."

With PI detectors it is the voltage spike that presents many problems. The coil is "ringing" after the spike and needs to calm down before the detector goes into receive mode to look for targets. This historically has limited PI detector ability to find tiny gold nuggets. The SDC 2300 works by minimizing this delay time, enhancing its ability to find small gold.

The GPZ works it's magic by never shutting the current off. Instead, the polarity is reversed by the circuit with no spike occurring and no delay needed other than whatever the engineer desires. Instead of the signal decay being measured from the moment the current shuts down, it now is measured from the moment the polarity reverses.

Where Minelab loses me is in explaining how the signal decay in the target can actually decay if the current never shuts off. The target is constantly "illuminated". I assume it has to do with the reversal of the polarity but I am not clear on this point. Minelab is still working in the time domain here and so the detector acts like a PI detector.

However, eliminating that spike and working with a continuous current has many benefits. I was told that the ground itself is energized by that spike and the elimination causes the ground to be less resonant with the electronic field that is being produced. Reducing the ground effect is one huge benefit, as is reducing any need to dampen or deal with the transient voltage spike, allowing for easy detection of small gold. At the same time the continuous field that is produced is more consistent in that it does not ebb and flow like a pulse field. Again, this can help with detecting small gold.

Oh yeah, ZVT. The reversal of polarity takes place at the instant when the current is at zero voltage. You cannot shut current off instantly but you can turn it on a dime at the instant of zero voltage. It makes for a cool sounding acronym - Minelab loves acronyms - and so ZVT.

In a nutshell I think it is the elimination of the transient voltage spike and the issues related to it that is producing benefits here. A layman trying to explain things in layman terms but I think that is the gist of it without mangling it too bad. I am sure brighter minds than mine will have issues with some of what I have said and I truly hope somebody that knows better can chime in and explain it better yet still in terms most people can understand. If nothing else, I do know we will see a paper from Bruce Candy very soon explaining it all, so stay tuned.

[Hotrock]

Hi AussieMatt, see the thread further below labeled ZVT technology. http://www.detectorprospector.com/forum/topic/682-zero-voltage-transmission-zvt/ It might address some of the answers to your questions. It's not necessarily a pulse induction, but behaves as a pulse induction because of a timing marker being introduced. The difference in the two, is the way the signal processing technique is done with CW (continuous wave).

The different tones of targets is a function of target pearmability.

This is just my understanding of this kind of technology based on what I know, and what has been let out of the bag so far. I could have some things wrong though.

[Ringmoney]

What is don't understand is why it does not have any sort of discrimination? For starters it measures the target response in the time domain so it should at least be possible to have a GPX type of discrimination? Secondly, since it transmits a VLF type signal, even though it is an alternating VLF type signal, should this tech not lend itself to some sort of VLF discrimination as well? The GPZ's closest living relative is Minelabs FBS/BBS units or Whites multiple frequency units, which have excellent discrimination, surely ZVT tech is very conducive to proper discrimiation?

 

Asking these questions to myself leads me to further questions,

1 Did Minelab rush the GPZ onto the market before another Manufacturer released their new tech? or

2 Are Minelab planning to squeeze more $ from its customers by introducing it at a later date?

[Steve Herschbach]

What is don't understand is why it does not have any sort of discrimination? For starters it measures the target response in the time domain so it should at least be possible to have a GPX type of discrimination? Secondly, since it transmits a VLF type signal, even though it is an alternating VLF type signal, should this tech not lend itself to some sort of VLF discrimination as well? The GPZ's closest living relative is Minelabs FBS/BBS units or Whites multiple frequency units, which have excellent discrimination, surely ZVT tech is very conducive to proper discrimiation?

 

Asking these questions to myself leads me to further questions,

1 Did Minelab rush the GPZ onto the market before another Manufacturer released their new tech? or

2 Are Minelab planning to squeeze more $ from its customers by introducing it at a later date?

Pretty hard to say rushed to market since this thing probably was conceived before the GPX 5000 came to market.

Discrimination seems an option. I always chuckle at the concept that any company should not be trying to make money. Minelab is owned by shareholders and they have a serious legal responsibility to look out for the interests of the shareholders. Any attention paid to customers has to be with that interest in mind. If I was running the show, and if I had a lead in the technology, I would absolutely not lay all my cards on the table at once. No responsible CEO does or he gets fired. I would say you can 100% expect new GPZ models every few years with new abilities and options, and that many of those abilities exist in the lab right this moment for delivery years from now. That is just how business works. In that regard I would not expect Minelab to be any different than any other corporation.

If Minelab had serious competition it might be another story. Usually companies are straining to leap frog each other. The only real competition Minelab seems to have when it comes to this technology is Minelab.

[Ringmoney]

Pretty hard to say rushed to market since this thing probably was conceived before the GPX 5000 came to market.

Discrimination seems an option. I always chuckle at the concept that any company should not be trying to make money. Minelab is owned by shareholders and they have a serious legal responsibility to look out for the interests of the shareholders. Any attention paid to customers has to be with that interest in mind. If I was running the show, and if I had a lead in the technology, I would absolutely not lay all my cards on the table at once. No responsible CEO does or he gets fired. I would say you can 100% expect new GPZ models every few years with new abilities and options, and that many of those abilities exist in the lab right this moment for delivery years from now. That is just how business works. In that regard I would not expect Minelab to be any different than any other corporation.

If Minelab had serious competition it might be another story. Usually companies are straining to leap frog each other. The only real competition Minelab seems to have when it comes to this technology is Minelab.

 

Don't know if it was conceived before the GPX was released as it was very hush hush within Minelab it self. They certainly had it squeezed into the CTX frame even before the CTX was released.

 

Totally agree that responsibility to shareholders is more important than loyalty to its customers for Minelab and that's how the corporate world works.

 

As for the competition, Minelab has the other manufacturer bent over backwards for years with its approved patents blocking the rest, but looking at the latest patents from Whites, their new tech looks very similar to that of the GPZ and maybe more conducive to discrimination makes you think twice, was it a rush job. 

 

On the other hand, when you see that AKA are very close to introducing a multi frequency detector and XP have one in the pipeline as well, are we finally going to see Minelab's dominance in that market coming to an end as well. Minelab never considered that the XP Deus  was going to be a threat at all but around 75% of all relic hunters in the UK and Europe are using them now, and they are making great roads in the US as well. Alain Loubet  of XP promised to wipe the smile off Minelab's face, how right was he?  The thing is, are Whites and others going to give Minelab a kick in the ass as well?

[AussieMatt]

Thanks for the replies fellas.

Hopefully Bruce will get that paper out to clarify it all.

[Hotrock]

What is don't understand is why it does not have any sort of discrimination? For starters it measures the target response in the time domain so it should at least be possible to have a GPX type of discrimination? Secondly, since it transmits a VLF type signal, even though it is an alternating VLF type signal, should this tech not lend itself to some sort of VLF discrimination as well? The GPZ's closest living relative is Minelabs FBS/BBS units or Whites multiple frequency units, which have excellent discrimination, surely ZVT tech is very conducive to proper discrimiation?

The GPZ could someday have the capability of switching back and forth from the Time Domain (PI) type of target processing to the Frequency Domain (VLF) type of processing at the operator's command. This feature would require no hardware design changes. Or if the signal processing is designed to accommodate both types of signals, then the targets could be displayed as Frequency Domain (FD) detected and/or Time Domain (TD) detected, simultaneously. Indication of both types of detections to the operator could be displayed. Only targets that have certain characteristics may be detected in both modes. Both FD and TD modes. This could be viewed as an additional target discrimination feature.

[Tom Harris]

Steve

Thanks for that explanation. The 7 min. video with BC flipping the magnet over top of the coil now makes sense to me.

It seems like such a simple thing but Mr. Candy is first again. He's the Steven Jobs of metal detectors, everybody is always trying to catch him.

Tom

[Sourdough Scott]

Not a technical question. But being tall at 6'5". One thing I liked about the GPX 5000 was able to customize it with a longer upper or lower shaft. wondering how the ZED would fit me? Guess I got to find someone to get the feel for it.