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GPZ 7000 Pi Or………..???


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50 minutes ago, phrunt said:

ZVT is at the infancy, there would have to be so much more they can do with it. PI, not so much.

'ZVT' is still a pulse induction detector. A very fancy and highly advanced BiPolar PI, using a DOD coil...but a PI still at its heart.

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23 minutes ago, Aureous said:

'ZVT' is still a pulse induction detector. A very fancy and highly advanced BiPolar PI, using a DOD coil...but a PI still at its heart.

Are you sure, it's so confusing in their documents it's hard to know, they're very much trying to differentiate it here

They say it's continuous wave where as PI is not.

Another disadvantage of PI is its capability at detecting very
large nuggets compared to CW metal detectors, such as ZVT.
CW means Continuous Wave and includes all technologies
that do not have zero transmit periods (almost all technologies
other than PI).


Zero Voltage Transmission (ZVT) – ZVT has the same major
advantage as PI for ground balancing in not detecting the
major soil component X, but has the same advantage of CW
metal detector technologies compared to PI for detecting very
large nuggets because ZVT is CW (unlike PI that is not CW), and
also the same advantage as PI for being relatively insensitive to
saline soils compared to VLF.

What is the ZVT transmitted field, and how does it differ to PI?

Both ZVT and PI measure a signal (receive signal) immediately
after a very rapid change in magnetic field. During the receiving
(measuring) period, PI does not transmit a magnetic field at
all, whereas ZVT transmits an exceptionally constant magnetic
field (until the next very rapid change in magnetic field occurs).
The ZVT transmitted field alternates between transmitting
very steadily in one direction; e.g. North Pole pointing into the
ground; then rapidly switches to South Pole pointing steadily
into the ground, then back to North and so on.

zvt.jpg.9402613ca7d855d1b72d3da59ecbe051.jpg

Figure 2 shows a comparison between the ZVT VRM soil signal
and the nearest equivalent PI soil VRM signal; both transmitted
magnetic signals being bi‑polar, with the same fundamental
frequency and same rapid change of magnetic field period. It
should be noted that the PI receive period is half that of the ZVT
period, because the PI system shown in figure 2 transmits for
half the time and receives for the other half of the time, unlike
ZVT that transmits and receives simultaneously just about all of
the time. The important difference in the VRM signals is that the
PI signal decays away substantially faster than the ZVT system.
This indicates that the receive signal for PI is less sensitive to
longer Time Constant (TC) components compared to shorter
TC targets than ZVT, and this is one of the main reasons why
ZVT technology is better at detecting large nuggets compared
to PI; another main reason being from the double length
receive period in ZVT compared to PI for the same fundamental
frequency.

I can easily get lost in their technical mumbo jumbo.

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As explained on video by Bruce Candy himself, right at the release date of the 7000, the GPZ detects eddy currents from the targets received (PI tech) it doesnt have a complete switch off cycle like a PI though, because BiPolar PI's simply switch rapidly between field changes, so there's a constant (almost) 'wave' of transmit energy. So, instead of a complete switch off cycle to allow for the Rx to determine a target, the field change allows the extraction of the ground signal (thanks to the clever use of DOD coils) and the eddy current is then detected. Everyone can easily hear the similarity in audio response between GPX's and GPZ's....the same multi channel signal responses (MPS PI tech) and so on.... Minelab have a strong history in shrouding their tech with acronyms and long winded wording...and very wise too. Its smart and clever and shrouds the tech against those companies and countries who would steal and copy at the developers expense. No critique here...just telling it for what it is. 

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Good discussion guys. I think there is big difference in what "pulse" means for both PI and ZVT. For regular PI machines there is an "off time" for receiving (hence the word pulse) whereas for ZVT the term "pulse" refers to just switching the pole of the magnetic field while continuously transmitting  (no off-time). Hence, in my view the 7000 is not a PI machine in it's conventional definition and should not be called as such. In contrast, the 6000 is still a "conventional" PI (with off times in between pulses for receiving), so the same advantages (or shall I say differences) that ZVT has over PI will remain in effect when comparing the 7000 with the 6000. This is the reason why I don't think the king trophy discussion makes much sense, both detectors are really so different. Now, when it comes to all the other stuff (weight, ergonomics, coil variety, easiness of use for beginners, etc.) then you can call the 6000 a king. You can also call it king (or god...!) if your primary focus is super fast timing gold in shallow to medium depth ground. However, the ZVT technology will always have distinct advantages that will not be reached by any conventional PI machine and the 7000 could equally be called king, just in a different kingdom. Even with a newer GPZ version released the differences between PI and ZVT will remain fundamental, hence the 6000 will likely remain king in it's kingdom, even after the "GPZ 8000" has been released. In summary, ZVT is not an old obsolete technology and calling it outdated is simply not accurate (IMHO). Just my 2 ct.

GC  

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I find it virtually impossible to understand ML's patents and other technical writing. It's like it's intentionally obfuscated and confusing in a way.

The way I understand ZVT is as a semi-hybrid. ZVT uses a continuous wave very much like a VLF (but not necessarily a nice sine wave), but it still samples like a PI - ie, looking at target signal decay and not signal phase offsets like a VLF. But it samples during the transition from positive to negative instead of only having positive pulses and then periods of "silence" with no pulse where the machine does nothing but listen to signal decay like a pure PI does.

If that's the case then it seems like you could selectively choose which mode to sample with on a ZVT machine - more PI like for raw depth and ground immunity, or more VLF like for some level of discrim and ultra-sensitivity to speci stuff. 

Again, if that's also the case, then with enough processing power to control mode switching, you might be able to effectively operate both types of detectors simultaneously and have the computer filter the bad parts of each mode out while only giving the operator the good parts of each mode. At least, that's my hope with something like the 8000, with regards to adding some usable discrim.

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Well they clearly point out the ZVT is always going to be better than PI for depth on bigger deeper gold and we're seeing that with the focus on the 6000 being away from that gold.

It looks to me like they do plan on doing a GPZ 8000 and not stopping ZVT in favour of PI which I believe would be a massive mistake.  Just slapping a small coil on ZVT has proven it holds its own or I believe beat a PI machine designed for finding small gold, the GPZ didn't need anything else done, just a coil change to accomplish this.  It shows there is a lot going on under the hood.  So if they were to make a GPZ 8000 and tweak it a bit more and release it with a range of coil sizes I think I'd be buying it, at the moment I don't think I am interested in buying anymore Minelab Gold Detectors, this mouse has jumped off the wheel.  They jumps in technology are no longer enough for me to justify the price for my needs and I'm super happy with my current gear.

If the PI's like the 6000 are beating ZVT on specimen gold perhaps that's something they need to work on and improve, they clearly improved on it over the 5000 to the 6000 as it appears the 5000 was pretty poor on it.  The SDC was better on it so they knew what they had to do with PI I guess.

My question is with ZVT being a bit of a hybrid almost VLF like detector is that the technology that could finally bring good discrimination and even the holy grail Target ID's to a detector like that? I hope I see that sort of thing in my lifetime.  A coin capable Target ID detector with the depth of the GPZ would be outstanding and a real game changer the world over.  People who don't think there are deep coins just haven't found any in the ground with the current technology, they're often there hiding away especially in places with softer soil or an ancient history.

VLF's were trying to make us buy a detector for tasks like separate gold detectors and coin and jewellery detectors, over time this was no longer viable and they merged into one.  Now we have multi purpose detectors that are as good or better than single purpose detectors, I would be as happy as can be if this also happened with high end gold detectors also becoming coil, jewellery, relic detectors for all environments.   Minelab has seen in their bottom line coin and jewellery is where it's at for making money lately, so who knows what the future holds.

Everything I've read leads me to believe ZVT isn't classified as PI, but it's so hard to understand what they're saying for my brain, it makes it hurt.

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I just hope we don't enter another era of marginally eeking out small tech gains with each new $10k detector, sorta like we saw when I first started paying attention to detectors around the time the 3500 was king. The 4000 was...eh. The 4500 was enough to convince me to buy an expensive machine and start playing the PI game (I had a GMT only at the time) but it wasn't that much better than the 3500's people I knew were using, honestly. The 5000 left me ho-hum and I went back to the 4500 since I didn't need Fine Gold and I didn't see a lot of stability improvement to make the price tag worth holding.

I get the feeling that's kinda what they are looking at doing with ZVT, and if that's the case, I'm losing interest in the game. I'd take a lightweight 7000 equivalent, sell my 6 and 7, and probably call it good there.

Everything I've read leads me to believe that discrim is entirely possible on hybrid type machines. That we've had to wait and wait and wait makes me wonder if I'm either wrong (very likely), or ML is just playing a game milking tech improvements out again like with the old GPX game. 7 years since the Z release...? That's an eon in the tech world. Either way, I feel my excitement for new machines sapping and going away lately compared to how I felt about seeing what the future might hold after the Z first came out.

I'm saying this all as a guy sitting squarely in the USA though. I'm guessing in Australia and other places in the world where nuggets are still more numerous, people might not look at it the same way.

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There is definitely a pulse with a Zed, albeit a very fast one- you can hear it when it’s transmitting next to a radio antenna, especially AM radios.

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Last thing I'll say is that the range of frequencies Tx'd from the GPZ is in the hundreds of Hz (800-900) which is perfectly within the typical PI range as well. The only CW portion of the equation is that the wave is indeed 'constant', without any pauses. Its still a PI at heart. A very clever, hybrid, practical PI. If it sounds like a duck, looks like a duck and feels like a duck....its probably a duck.

 

Thanks to Steve for dissecting this discussion from another thread and keeping it separate. Again, no critique of the GPZ or ZVT tech whatsoever, its brilliant! Smart, clever and exactly what we need to further the technology spectrum for finding gold. It now needs to be expanded upon and adapted into a lighter-weight form with better coils and (probably) adapted to use the Brilliant Geosense tech as well.

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Conventional PIs receive in off time, the GPZ does'nt. Conventional PIs transmit with voltage, the GPZ does'nt. To me this is a very different duck. 😁 But hey, it really does'nt matter how you call it and we are probably all right, nobody is wrong. Let's just call it an awesome machine, and with a modern design and some tweaks this should be the next king (in it's own kingdom). 👍

GC

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