Super D Coil design, and ZVT on the GPZ7000

[TheSleeper]

Does anyone have any insider knowledge on this? Blue are quotes from Minelab, Red are areas in question.

The Super - D smart coil consist of a central transmit winding and two outer receive windings. This configuration greatly decreases interference from magnetic soils, reducing ground noise.

This is a dramatic change from the current DD design, and makes me wonder if this is the main reason the GPZ is reaching the depths ML is claiming. But also brings up another question which is combined with the next quote from ML.

ZVT (Zero Voltage Transmission ) creates ultra - constant high-power opposite polarity magnetic fields, increasing gold sensitivity. This innovative technology detects gold nuggets at extreme depths.


I have highlighted two parts above in red to draw your attention to them. Here is all I could find about opposite polarity:

Via a demagnetizing magnetic field: permanent magnets exhibit a characteristic called coercivity, which is the ability of a material to withstand being demagnetized by an applied magnetic field. Modern permanent magnet materials such as Sm-Co and Nd-Fe-B have high coercivities; older materials such as Alnico or ceramic [hard ferrite] materials have lower coercivities. With a strong enough magnetic field of opposite polarity, it is therefore possible to demagnetize the magnet [whether this comes from another permanent magnet, or a solenoid]. Interestingly, an opposing magnetic field is sometimes applied to a magnet in order to 'knock it down', or to lower its overall magnetic output, so that it can be used appropriately in an application.

Disclaimer: I am not a scientist nor engineer, but to me this in layman terms means, the GPZ puts out an opposite polarity field to de magnetize the magnetic soil you are hunting on thus rendering it silent to the machine.

A lot of you guys are a lot smarter than me so pitch in here and help a dummy out with your knowledge.

 

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[DDancer]

Been moving cross country or I would have talked to you sooner Sleeper,
In a nut shell part of what the zvt tech is doing can be related to noise cancelling like Bose headsets do for sound. So your simile about de-magnetizing the soil is not a completely wrong way to think about it. What the tech does is not cancel out the magnetic field of the soil but attempt to cancel out the currents induced into the soil by the transmission cycle. The result is much like you said~ it renders the soil silent to the machine.
While currents do generate magnetic fields and the collapse of those fields in turn generates magnetic fields *which is what the detector listens for* the time lag between these events is what has hindered current PI detectors. In current PI's not only does the detector have to wait for the ground effect to die down but it also has to wait for the effect to die down on the receive circuit coils *these are often one in the same coil*. The effect is call "ringing" and it limits the sensitivity of current PI systems. The ZVT and the design of the Super DD coil does two things. ZVT's constant switching current effectively negates soil conditions as well as ringing in the receiver coils and the DD design has separated the transmit and receive coils giving it faster switching time to listed for the "ringing" of metallic objects. The result is higher sensitivity.
That's pretty much the nutshell explanation that I've seen and figured out for this new detector system. To understand it better take a look at the science for how electricity is created and look at the relationships between Voltage/Current and how and why magnetic fields are created. The use of voltage and current to create a magnetic field is similar to that of permanent magnets however there is a big difference in how the are used for detection or energy creations.

 

[TheSleeper]

Thank you Dancer for your reply, gonna take a lil while to digest what you have written.

My main concern or interest shall we say is with the new coil design. I am really intrigued with this triple coil design and if it will filter down into lower lvl machines. Or even if it would be beneficial to a lower lvl machine like the explorer series ie: Etrac or its next manifestation, if there is one. A triple D design with two transmit coils and the center receive beam design of the DD does sound interesting. Just not sure if it would afford any deeper depth penetration using the current send/receive design.

Best example I can think of, would be even though the current bred of detectors are not designed for it without the zvt, an explorer with the triple D coil, if since there are two dedicated transmit coils and one receive coil if that design would hit deeper then the same machine utilizing a DD coil, per say the machine was modded to utilize both transmit coils instead of just one.

Humm I'm rambling here, mind is really going into overdrive pertaining to this and the future we will see from ML.

 

[DDancer]

The design for the super DD is that of one transmit and two receive coils. When I first read the patent, before any real info came out, I thought it was a dual transmit single receiver myself. After the info came out I realized I was mistaken and after some small thought it made sense. There is no good reason to have dual tansmit coils however the zvt tech is essentially doing this with one coil due to its modulation. The dual recievers make sense to me as they are most likely averaging the ground signal to help further nullify it and provide extra coverage for true targets. I also suspect that the recievers are also modifying the transmit function for a higher level of performance and GB.

As to how the super DD might be used on other machines~ I've not considered it. Its unique in how it performs and a hefty amount of that performance is built into the software.

 

[TheSleeper]

Humm ok see what your saying. With the central transmit coil pulsing straight down, the two receive coils alternate the receive signal between them, forming almost a psudaquasy (sp) 3-d picture into the ground, the software comparing the signal each receive coil acquires, then compares each signal forming a picture beneath the coil. With the two receive coils beside the transmit coil, it could almost be looking at the targets in a 3-d manner, like this \|/

 

[DDancer]

It would be interesting if there were some imaging like what your describing however that's not the case. The coils nor the software are capable of any vector information nor does it appear at this time that the zvt tech can achieve time domain information for depth. However with the GPZ switching between modes of search can give some indication of depth and size and this has been reported infrequently. Modern PI's can do this as well. ZVT tech's coil set up appears to be primarily set up for negation of undesired current "ringing" in the search media *soil* via the modulation of the transmission and sampling by the receive side and increased sensitivity to ringing of targets.
I don't see how a super DD coil might benefit a VLF or modern PI. Additional recievers on a VLF may work but the integration is a problem also additional transmitters have been used for VLF and with some success. However they are independent of the primary machine and work as illuminators. On a Modern PI I don't see as there would be any benefit of moding it for a super DD as you would be forced to use the zvt switching of its current and the end result is no longer a PI but a Zed The hardware just wont support what a ZVT does. Then there's the software and I expect theres a lot of data manipulation to make it work.

 

[TheSleeper]

Interesting DD thank you for your insight.

 

[timemachine]

Thank you, DDancer for that wonderful explanation. Have your work/travels afforded you the opportunity to visit WA State at all?