GPZ 10" Xcoils In USA

[Andyy]

On 7/4/2019 at 7:10 PM, Chet said:

I look forward to giving them a run in some heavily detected areas.

Sounds good, Chet.  Maybe between you me and Jason,  we'll find what the best method of ferrite balance will be in saturated ground.

[Chet]

Referencing this patent; which discusses the GPZ 7000 and possible coil options;

United States Patent Application 20130154649 
CANDY; Bruce Halcro 
June 20, 2013 
TRANSMIT SIGNAL OF A METAL DETECTOR 

In searching using edit and find functions for the word “Saturation” and “X” it came up with references that place the Transmit coil 2cm above the receive coil to reduce saturation of the soil. 

This 2 cm is important in highly mineralized ground that effects the processing of the X signal response. 

The X signal occurs from non-linear reactions of magnetic components of saturable ground that have the property of viscous superparamagnetism.

Superparamagnetism is a form of magnetism which appears in small ferromagnetic or ferrimagnetic nanoparticles. 

It is important for the GPZ 7000 to avoid saturation of the soil so as to reduce the X signal response to a manageable level that can be processed out and allow weak gold responses to be processed.

What may be happening with the X coils on highly mineralized ground? Going by the descriptions stated in the forums; the coils are flatter than the factory coils. 

This implies that the 2 cm separation between the lower receive coils and the upper transmit coil is not there. This would allow the transmit coil to be closer to the soil and disturb the X signal response when over highly mineralized soil.

A possible solution that should be tried in the field on hot ground is to swing the coil 2 cm/0.79 in. higher than normal. 

Some experimenting may be required to resolve the problem that Andy had with the 10” X coil. Perhaps ferrite balancing on quiet soil or in the air. Once it is accomplished it is stored and will return to the same setting when powered up again. 

Have a good day,
Chet

[jasong]

That sounds like a pretty dang good guess about how the X Coils are achieving some higher sensitivity, nice catch.

58 minutes ago, Chet said:

A possible solution that should be tried in the field on hot ground is to swing the coil 2 cm/0.79 in. higher than normal. 

Some experimenting may be required to resolve the problem that Andy had with the 10” X coil. Perhaps ferrite balancing on quiet soil or in the air. Once it is accomplished it is stored and will return to the same setting when powered up again. 

Have a good day,
Chet

Good idea, and pretty easy to try. 

*Had a question here for you but I answered it myself Googling, so deleted. 

[Andyy]

On July 4, 2019 at 2:54 PM, Jonathan Porter said:

To check for saturation noise, ground balance the coil in Semi-Auto mode and then place the GB in Manual mode. Bring the coil to the ground and then place the coil directly on the ground (couple the coil to the ground), listen to the threshold as you do this, then pull the coil briskly up and away 8 to 10 inches and take note of the signal created as you couple and pull away, the louder this is the greater the saturation signal will be. You CANNOT ground balance out Saturation signal, you have to keep the coil just above it to avoid depth reducing noise.

JP

So is Saturation Signal just ground noise that the machine cannot balance?   (is it moisture)  I understand it is different than the X-signal but can be greatly magnified by the ferrite.   Is it part of the G-signal?  I'm not sure if I am clearly expressing my question.  In the past I had always thought there was:

1) ground noise (mineralization) including:

     a) X signal component (requires ferrite to remove this component)

     b) G signal component 

2) EMI (ElectroMagnetic Interference- air wave noise)

Is there a 1c) Saturation?

 

 

[jasong]

I would really like to hear what JP says too since I'm getting really confused with what exactly X and G entail also, and there seems to be conflicting bits of information all over the place in various posts.

From a physics standpoint: saturation should be the point on the magnetization curve where any permeable ferrous or ferrite mineral stops increasing the B field exponentially when an external mag field is applied, ie where all it's domains have already been aligned with the external magnetic field. Therefore, unless I am misunderstanding it, saturation is not a response itself, it just affects the X response as the ferrous or ferrite materials go in an out of saturation as the applied magnetic field from the GPZ changes.

For sake of defintion (someone please correct this if not accurate) - ferrous and ferrite materials are natural occuring oxides of iron most commonly for our purposes. AKA - hot ground. But ferrites can be a lot of other things also that we don't encounter as commonly.

That being the case, I am struggling to understand how salt affects the X balance and requires one to toss the ferrite down again since there are no ferrous or ferrite components in salt, but this has been said many times over as if it's understood somehow that salt will throw the X balance off. I cannot find a proper definition of what exactly G is tracking and it needs to be defined in order to understand this all I think. I asked a few times in the past... It doesn't appear to be anything scientific specifically that I can find, but something related to detectors so someone with knowledge of detector engineering would need to define it.

I don't get if X is only ferrite and G includes non-ferrite permeable materials like magnetites, pyrites, etc. Or if X encompasses all ferrite/ferrous materials and G only includes the conductive response of the ground? Or...?

[cobill]

Jason, read page 2 for more about X (ferrite component) and G (ground component) and the New Ground Balance Mode options. Not much technical stuff, but it helped me some.

https://www.minelab.com/__files/f/313856/4907-0942-1 Brochure, GPZ 7000 Software Upgrade No.2 EN.pdf

Bill

[jasong]

I've read it inside and out, and every post I can find. A lot of stuff seems to conflict to the point I don't feel I can even ask a proper question first anymore until we get some basic defintions of what these things are we are talking about and why/when exactly we need to be using certain tracking modes and the ferrite.

The only reason I'm looking more into it and asking is because JP's mentioning all the stuff. Otherwise, I was pretty content just staying in auto tracking and never using the ferrite at all. But lately we were told that we are unobservant operators if we see no need to use the ferrite and we can't tell the ferrite balance is going out. I have not observed Auto ever failing to balance within a second or two on my soils except in a few instances, and in those instance the QT button tracked it back within a few seconds of moving the coil around.

I suspect that some of this applies more to hotter soils in Australia than in many places in the US (other than perhaps South and Central AZ). But it would be good to get some clarification on that too if that is the case. That brings up another question I've had - why do we even need to use the ferrite at all if there is little to no ferrite component in our soils?

I have 20 or 30 questions right now, but I'm not even sure if they are real questions since I don't have the underlying fundamental defintion of what variables represent to even know if it should be asked or not. For instance - why do I even need to use the ferrite in Auto if the ferrite component is actively tracking?

[madtuna]

Yep...I don’t worry about all this alphabet stuff, I just get out there and do what works for me. But then I might be one of these crap detector operators I’ve been reading about lately.

while it’s great having all this knowledge about how the detector works, I’d prefer to master how to work it and I’m getting there by experimenting, testing, swinging the damn thing and experience.

Often the more you read about X, G, Y etc..the more confuddled you get, the more self doubt you create and therefore the less success and enjoyment you have.

[Andyy]

3 hours ago, jasong said:

From a physics standpoint: saturation should be the point on the magnetization curve where any permeable ferrous or ferrite mineral stops increasing the B field exponentially when an external mag field is applied, ie where all it's domains have already been aligned with the external magnetic field. Therefore, unless I am misunderstanding it, saturation is not a response itself, it just affects the X response as the ferrous or ferrite materials go in an out of saturation as the applied magnetic field from the GPZ changes.

Right, this makes some sense since saturation cannot be balanced out according to JP.   Saturation means you have spillover from something  which I have to assume is limited by the magnetic field of the coil.  Therefore maybe it is all of the left over "saturated" signal that cannot be handled.  I don't know.

Honestly, though, I had never heard of high saturation until the Xcoil came out.  So, yes, I am still confused.

[jasong]

I thought it made sense too Andy, but... I was literally just typing up a response about an experiment I did to see if it made a little more sense in physical observations, I'll still post it but I apologize in advance for it going kinda off the rails and certainly no one needs to read this to understand their GPZ.

"On a mildly tangential note, I decided to do a crude experiment after reading up on superparamagnetism via Chet's post. I have some ferrofluid which will show magnetic interactions well under the field intensitities which something like magnetite will physically saturate. It is also superparagmagnetic, technically speaking. So I put a plastic container full of ferrofluid on top of my GPZ coil expecting to see some kind of minor oscillations or something. But no result.

Probably has something to do with the mag field alternating or something with ZVT that I don't understand where things cancel each other out, or maybe the GPZ works off EM radiation and not mag field interactions, I really have no idea.

But now I'm wondering how we can even be saturating minerals under the coil at all since the mag field of the TX coil seems to be relatively small, certainly not in the 1+ tesla range. I'm sure I'm mixing something up here with alternating mag fields and EM radiation vs permanent fields and whatnot. But are we even really emitting a mag field powerful enough to saturate ferrous minerals is what I'm wondering? And if not, is the physical definition of saturation not what Minelab is talking about?

Further, saturation point implies very little mag field change in the ferrite/ferrous material with increased TX strength, which should be a good thing. Less ground noise. So why do we want to avoid it? Would it be best to just saturate the crap out of the ground since everything past that point generates very little noise? Like the B curve for magnetite is almost flat after saturation even if you quadruple the external mag field, whereas up to that point the saturation effects B exponentially...

Just. So. Many. Questions. Some major definitions or pieces of data are missing otherwise this wouldn't be so confusing to me."