GPZ 7000 Successor, March 9th boys…. Apply for those second mortgages…

[Carl-NC]

An otherwise technically correct and informative post becomes the target of illiterate, rude, offensive innuendo.

Sorry, didn't mean to upset you, but your technically correct post was incorrect. Glad to discuss further if you like. Not interested in making it personal.

 

[DizzyDigger]

Sorry, didn't mean to upset you, but your technically correct post was incorrect. Glad to discuss further if you like. Not interested in making it personal.

Carl, you said nothing worth anyone getting upset over.

Although your technical discussion is miles above my pay grade, I do know that
if you were to put 100 EE's into a room together, they'll find something to argue over
in a heartbeat.

 

[Treasure_Hunter]

Post deleted, Geo, if you have issue with comment please report it to mod to be looked at, dont insult another member. I looked at Carl's post, there is nothing wrong with it, it doesn't violate our rules and he is not insulting you.

Now I dont hunt gold nuggets, I'm a beach hunter, but I did find just the small gold lobster clasp to a small necklace with my excal with 15" WOT coil and it was on surface of beach and weighed less than a half gram.

 

[geowizard]

Getting the train back on the track;

Electromagnetic induction is central to the art and science of metal detecting. The concept of induction goes back to Michael Faraday.

He probably never thought about metal detecting. Metal detectors operate on this rather simple relationship between electrons and magnetism. Our world as we know it runs on induction. The lighting in our homes comes mostly from generators. The electricity runs appliances. blenders, mixers and every electric motor uses induction to convert electricity into a magnetic field having force to rotate the motors. You can't see it. You can feel it. Electric energy is converted to magnetic force. This interaction of electricity and magnetism is referred to as electromagnetism.

When an electric current flows in a conductor, a magnetic field is created. Wrap a wire around a nail and connect a battery and you have a magnet. It is called an electromagnet.

- Geowizard

 

[geowizard]

Taking the discussion to "Tech Talk";

Minelab GPZ8000 Deep Dive

New designs incorporate new "features" that can frustrate new users! :hello: The result is in many cases a less than flattering review. Lets do a deep dive into the GPZ 8000 and discuss the technology and where that technology is found in Minelab predecessors. - Geowizard

www.treasurenet.com

- Geowizard

 

[Jennifer-007]

Jen,
The missed sunbakers are the issue with the GPZ 8000. The large coil, high power design has trade-offs. One tradeoff as Bruce Candy explains is detecting small gold at the surface in a detector having this profile. It just came out and as you cited earlier a sh*tload of reviews are not good. Really! There are explanations for the bad reviews. This is an example of using the wrong tool and blaming the tool for not doing a job it wasn't supposed to do.

- Geowizard

You stated PI detectors like the GPZ 8000 miss nuggets, you did not state the GPZ 8000 specifically, which is not a traditional PI. I shared those videos to show that both true PI as well as ZVT as used on the 7000 and 8000 have no problem with sunbakers. I think generalizing the issue to be based on the technology itself might be short sighted, especially with such a massive change in coil technology as is used in the 8000.

The Minelab GPZ 8000 is not a traditional Pulse Induction (PI) machine. Instead, it uses Minelab’s proprietary GeoZVT™ (Zero Voltage Transmission) technology, which is the next-generation evolution of the ZVT platform first introduced with the GPZ 7000.

Here is how it differs from standard PI technology:

• The Technology Gap: Conventional Pulse Induction detectors work by sending a powerful pulse of electrical current into the ground, abruptly turning it off, and listening for the signal decay from a metallic target. While excellent for punching through highly mineralized ground, PI can sometimes lack sensitivity to very fine, sub-gram gold.
• The GeoZVT™ Hybrid: GeoZVT is engineered to bridge the gap between the extreme depth of PI and the hyper-sensitivity of Very Low Frequency (VLF) detectors. It operates with a continuous, opposite-polarity transmission that significantly increases depth while maintaining high target sensitivity.
• Concentric Toroidal Coils: The GPZ 8000 pairs this technology with a new "Z-Set" concentric toroidal coil system (rather than the Monoloop or DD coils common on PI machines). This specialized coil architecture actively works with the GeoZVT processing to cancel out ground noise and stabilize performance in difficult soils.

Here’s how it breaks down:

• Pulse Induction (Traditional PI):
  • Sends pulses into the ground and measures decay
  • Great in mineralized soil, but limited target ID and sometimes less depth on certain gold
• ZVT (what the GPZ 8000 uses):
  • A different, proprietary tech from Minelab
  • Generates continuous opposing magnetic fields instead of pulses
  • Designed to combine PI-like depth with improved sensitivity and stability

So what is it, really?

Think of ZVT as: “Beyond PI” rather than PI itself

• It’s not VLF
• It’s not traditional PI
• It’s its own category, though it borrows strengths from both

Ultimately, it acts as a hybrid system that gives prospectors the heavy-duty mineral rejection and depth of a high-end PI machine, while maintaining the sharp sensitivity required to hit fine, small gold.

 

[geowizard]

View attachment 2249074
You stated PI detectors like the GPZ 8000 miss nuggets, you did not state the GPZ 8000 specifically, which is not PI. I shared those videos to show that both true PI as well as ZVT as used on the 7000 and 8000 have no problem with sunbakers. I think generalizing the issue to be based on the technology itself might be short sighted, especially with such a massive change in coil technology as is used in the 8000.

The Minelab GPZ 8000 is not a traditional Pulse Induction (PI) machine. Instead, it uses Minelab’s proprietary GeoZVT™ (Zero Voltage Transmission) technology, which is the next-generation evolution of the ZVT platform first introduced with the GPZ 7000.

Here is how it differs from standard PI technology:

• The Technology Gap: Conventional Pulse Induction detectors work by sending a powerful pulse of electrical current into the ground, abruptly turning it off, and listening for the signal decay from a metallic target. While excellent for punching through highly mineralized ground, PI can sometimes lack sensitivity to very fine, sub-gram gold.
• The GeoZVT™ Hybrid: GeoZVT is engineered to bridge the gap between the extreme depth of PI and the hyper-sensitivity of Very Low Frequency (VLF) detectors. It operates with a continuous, opposite-polarity transmission that significantly increases depth while maintaining high target sensitivity.
• Concentric Toroidal Coils: The GPZ 8000 pairs this technology with a new "Z-Set" concentric toroidal coil system (rather than the Monoloop or DD coils common on PI machines). This specialized coil architecture actively works with the GeoZVT processing to cancel out ground noise and stabilize performance in difficult soils.

Here’s how it breaks down:

• Pulse Induction (PI):
  • Sends pulses into the ground and measures decay
  • Great in mineralized soil, but limited target ID and sometimes less depth on certain gold
• ZVT (what the GPZ 8000 uses):
  • A different, proprietary tech from Minelab
  • Generates continuous opposing magnetic fields instead of pulses
  • Designed to combine PI-like depth with improved sensitivity and stability

So what is it, really?

Think of ZVT as: “Beyond PI” rather than PI itself

• It’s not VLF
• It’s not traditional PI
• It’s its own category, though it borrows strengths from both

Ultimately, it acts as a hybrid system that gives prospectors the heavy-duty mineral rejection and depth of a high-end PI machine, while maintaining the sharp sensitivity required to hit fine, small gold.

Jen,

Don't take my word for it.

I refer you to US Patent 20180106925 page 1 [0018] April 19, 2018. Related sheets show the waveforms.

Go to: https://ppubs.uspto.gov/basic/
Enter the patent number: 20180106925
Click [Search]
Roll down and click [PDF]
This patent is most relevant because it comes after the 6000 and 7000 which are circa 2015 models and is most likely incorporated in the 8000.

I also refer you to the discussion on the Tech Talk thread where Carl shares info.

Minelab GPZ8000 Deep Dive

New designs incorporate new "features" that can frustrate new users! :hello: The result is in many cases a less than flattering review. Lets do a deep dive into the GPZ 8000 and discuss the technology and where that technology is found in Minelab predecessors. - Geowizard

www.treasurenet.com

- Geowizard

 

[geowizard]

With reference to sunbakers, The reference above in paragraph [0020] going from page 1 to page 2 discusses the issue with short time targets that are missed because they happen immediately after the pulse and during the back emf (counter electromotive force) time.

- Geowizard

 

[Carl-NC]

The Minelab GPZ 8000 is not a traditional Pulse Induction (PI) machine.

Yet it is a form of pulse induction, called constant current PI (CCPI). Traditional PI apply a low voltage to the coil and the current has a relatively slow exponential turn-on, followed by a fast turn-off, like this:

The dead time after turn-off is where you look for the target response.

One form of CCPI simply makes the turn-on about as fast as the turn-off, and you can also make it bipolar:

This still works with a mono coil and you still look for the target after the turn-off edge. Minelab's CCPI eliminates the zero-current regions and looks like this:

You now look for the target after each transition, but because the transitions don't end with zero-current you can no longer use a mono coil, it has to be IB. Target responses are still time-domain exponentials and are still processed the same as with traditional PI.

You can even mix a traditional PI pulse with a CCPI pulse like Garrett does in the ATX and Axiom:

So, yes, GPZ is still PI.

 

[Carl-NC]

With reference to sunbakers, The reference above in paragraph [0020] going from page 1 to page 2 discusses the issue with short time targets that are missed because they happen immediately after the pulse and during the back emf (counter electromotive force) time.

Yes, but this has nothing to do with whether it is a surface target or a buried target.

 

[geowizard]

Yes, but this has nothing to do with whether it is a surface target or a buried target.

This is true! The reference to "sunbakers" is for simplicity but applies to all fast eddy, small, highly conductive targets that respond during the short term in time domain..

- Geowizard

 

[geowizard]

The recovery from a pulse in every pulse induction system involves the decay time of the ever present "back emf" also known as counter electromotive force (cemf). PI metal detectors are all affected by this! The fast collapsing electromagnetic field around the coil as the pulse turns off induces the counter emf. The larger the inductance of the coil, the larger the counter emf. Designers handle the problem with damping and clamping circuits to expedite the counter emf decay. But... it still creates a problem in system timing for gating a sensitive receiver to acquire (listen) for an early response. The counter EMF is a very high voltage pulse that also is pounding the ground counteracting the eddy response from the original pulse! 🤓

- Geowizard

 

[geowizard]

Why?

Conservation of energy in PHYSICS dictates: "for every action, there is an opposite and equal reaction".

AI Overview:
Yes,
Counter-Electromotive Force (CEMF) is a direct manifestation of the conservation of energy. It acts as a feedback mechanism dictated by Lenz's Law, ensuring that the electrical energy input into a system is balanced by mechanical work and losses, rather than creating energy out of nowhere.


- Geowizard

 

[Carl-NC]

The counter EMF is a very high voltage pulse that also is pounding the ground counteracting the eddy response from the original pulse!

The flyback (CEMF) is just a result of suddenly turning off the current in the coil. It has no effect on target eddies. The flyback is just conservation of energy; the energy in the coil when it's on (E = 1/2*L*i^2) is converted to a capacitive voltage (E = 1/2*C*V^2) and they have to be equal. A typical flyback is 200V but can reach 1000V in some designs. The induced voltage from the target eddy response rides on top of the flyback decay and the RX uses a demodulator to separate them.

 

[geowizard]

The flyback (CEMF) is just a result of suddenly turning off the current in the coil. It has no effect on target eddies. The flyback is just conservation of energy; the energy in the coil when it's on (E = 1/2*L*i^2) is converted to a capacitive voltage (E = 1/2*C*V^2) and they have to be equal. A typical flyback is 200V but can reach 1000V in some designs. The induced voltage from the target eddy response rides on top of the flyback decay and the RX uses a demodulator to separate them.

Google AI and Geowizard both have it wrong.

Key Effects of Back EMF on Target Eddy Currents:

• Eddy Current Induction: The sudden collapse of the magnetic field (back EMF) creates a fast-moving, high-voltage change, which induces electrical currents (eddy currents) on the surface of nearby metallic objects.
• Decay Rate and Detection: The speed at which this back EMF decays allows PI detectors to sample the eddy current signals from targets after the transmitter pulse has died out. Targets with high conductivity produce slower-decaying eddy currents.
• Discrimination and Sensitivity: Residual back-EMF spikes can sometimes contaminate the target signal, making it difficult to detect small targets. Advanced PI systems use specific methods to minimize this back-EMF decay, which allows for earlier sampling and better detection of small, high-conductivity targets.
• Opposing Eddy Currents: Eddy currents created during the initial turn-off of the back EMF have an opposite polarity to those that might exist during a fast ramp-up, which can reduce target detection depth if not managed properly.

- Geowizard

 

[Carl-NC]

Google AI and Geowizard both have it wrong.

Key Effects of Back EMF on Target Eddy Currents:

• Eddy Current Induction: The sudden collapse of the magnetic field (back EMF) creates a fast-moving, high-voltage change, which induces electrical currents (eddy currents) on the surface of nearby metallic objects.

Yes, AI got this wrong. I find AI wrong quite often on metal detector theory. It is not the flyback voltage that induces eddy current. Eddies are generated by an induced EMF in the target, which is the result of a changing magnetic field, caused by a changing TX current:

dI/dt --> dB/dt --> dPhi/dt --> eddies

The flyback voltage is just an unwanted artifact. Also, we don't wait for the flyback to "die out" before looking for a target signal, we do that as the flyback is decaying:

Opposing Eddy Currents: Eddy currents created during the initial turn-off of the back EMF have an opposite polarity to those that might exist during a fast ramp-up, which can reduce target detection depth if not managed properly.

AI seems to get this backwards: eddies created during turn-off are the ones you want. The eddies created during turn-on are counter-productive and we try to minimize those by keeping the turn-on time at least 3x the tau of the target.

 

[thedogofdogs]

Awesome thanks for sharing!

 

[Jennifer-007]

Yet it is a form of pulse induction, called constant current PI (CCPI).

So, yes, GPZ is still PI.

You might want to reread what I actually wrote. I said it was not a “TRADITIONAL PI”, I never said it wasn’t a PI. I know adjectives can be tricky, but using one clearly implies it still belongs in the PI family. In other words… I appreciate the correction on something I never actually said. Pointing out that it isn’t a “traditional PI” inherently means I know it’s a PI. 😉

Jen

 

[Jennifer-007]

Jen,

Don't take my word for it.

I refer you to US Patent 20180106925 page 1 [0018] April 19, 2018. Related sheets show the waveforms.

Go to: https://ppubs.uspto.gov/basic/
Enter the patent number: 20180106925
Click [Search]
Roll down and click [PDF]
This patent is most relevant because it comes after the 6000 and 7000 which are circa 2015 models and is most likely incorporated in the 8000.

I also refer you to the discussion on the Tech Talk thread where Carl shares info.

Minelab GPZ8000 Deep Dive

New designs incorporate new "features" that can frustrate new users! :hello: The result is in many cases a less than flattering review. Lets do a deep dive into the GPZ 8000 and discuss the technology and where that technology is found in Minelab predecessors. - Geowizard

www.treasurenet.com

- Geowizard

Don’t take your word about what? Sunbakers? I don’t need to, I speak from personal experience, and I have other things to do than go chasing down rabbit holes on patent agency web sites in a futile attempt to prove myself wrong, but thanks.
Jen

 

[AstralDruid]

Well this is fun !!