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Ferrite Ring 8 Years Later


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5 minutes ago, BrokeInBendigo said:

I have a stock 14” and month-old 17” CC x-coil, believe it is bundle wound.

17" CC is spiral.

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23 hours ago, BrokeInBendigo said:

Thanks JP.
 

I have a stock 14” and month-old 17” CC x-coil, believe it is bundle wound (edit: tis spiral, thanks Simon). 

Out bush in reefy country with a lot of ironstone or red mudstone type bedrock I often get a fairly loud signal on the ferrite but on alluvial gravels or paddocks it’s less intense.

I’ve been running auto but understand the advantage of semi auto - I’ll try that and your suggestion about elevating the ferrite today. 

A lot of the X coils will not Ferrite balance properly especially in Normal timings, the best ones I used were the 15” Concentric’s they weren’t too bad, although a friend of mine has told me his recent 17”CC coil is very good too. The reefy country will most likely be saturation signal being magnified up the centre of the Ferrite, use the in-air approach assuming the coil and timings you select will allow it.

The GPZ14 coil should be able to ferrite balance in all timings (it is OK to have some small amount of signal but a loud target-like one is not good).

If you can achieve a reasonable X balance then I highly recommend you use the Semi-Auto GB mode, once locked the X calibration cannot shift unless the temperature of the electronics shift a lot (can only shift a few % points from dead cold), however if using Auto in some ground types you will only need to walk 20 meters in Auto and the conductive and saturation signals can throw the Calibration right out, this then has a flow on effect with the G balance which then tries its hardest to compensate but WILL fail.

In the conductive areas in the US (Nevada etc) the X signal is probably minimal and the Alkali the worst so the Auto mode should not be too badly affected by a bad X balance, best way to check is to pass the coil over a ferrite occasionally and see how loud the signal is, personally even though there is not much X present I would still be using Semi-Auto if for no other reason than it might give me a slight advantage over other operators.

My experiences in Arizona showed me there was plenty of X signal to be had in and around the Bradshaw mountains, even up at Rich hill there was plenty of ground that was variable (this was in the days before Smooth, GP3000 from memory) and I’m sure there would be plenty of X signal around. Mineralisation that forms gold that is then weathered has all the elements that can affect a metal detector no matter where in the world we work, if it didn’t then Americans would still be using VLF machines there would be no point to a PI. Case in point the new Garrett Axiom, obviously there is still a need for a PI in the US.

JP

 

 

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10 hours ago, Jonathan Porter said:

A lot of the X coils will not Ferrite balance properly especially in Normal timings, the best ones I used were the 15” Concentric’s they weren’t too bad, although a friend of mine has told me his recent 17”CC coil is very good too. The reefy country will most likely be saturation signal being magnified up the centre of the Ferrite, use the in-air approach assuming the coil and timings you select will allow it.

The GPZ14 coil should be able to ferrite balance in all timings (it is OK to have some small amount of signal but a loud target-like one is not good).

If you can achieve a reasonable X balance then I highly recommend you use the Semi-Auto GB mode, once locked the X calibration cannot shift unless the temperature of the electronics shift a lot (can only shift a few % points from dead cold), however if using Auto in some ground types you will only need to walk 20 meters in Auto and the conductive and saturation signals can throw the Calibration right out, this then has a flow on effect with the G balance which then tries its hardest to compensate but WILL fail.

In the conductive areas in the US (Nevada etc) the X signal is probably minimal and the Alkali the worst so the Auto mode should not be too badly affected by a bad X balance, best way to check is to pass the coil over a ferrite occasionally and see how loud the signal is, personally even though there is not much X present I would still be using Semi-Auto if for no other reason than it might give me a slight advantage over other operators.

My experiences in Arizona showed me there was plenty of X signal to be had in and around the Bradshaw mountains, even up at Rich hill there was plenty of ground that was variable (this was in the days before Smooth, GP3000 from memory) and I’m sure there would be plenty of X signal around. Mineralisation that forms gold that is then weathered has all the elements that can affect a metal detector no matter where in the world we work, if it didn’t then Americans would still be using VLF machines there would be no point to a PI. Case in point the new Garrett Axiom, obviously there is still a need for a PI in the US.

JP

 

 

Thanks for your detailed posts JP. 

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18 hours ago, Jonathan Porter said:

A lot of the X coils will not Ferrite balance properly especially in Normal timings, the best ones I used were the 15” Concentric’s they weren’t too bad, although a friend of mine has told me his recent 17”CC coil is very good too. The reefy country will most likely be saturation signal being magnified up the centre of the Ferrite, use the in-air approach assuming the coil and timings you select will allow it.

The GPZ14 coil should be able to ferrite balance in all timings (it is OK to have some small amount of signal but a loud target-like one is not good).

If you can achieve a reasonable X balance then I highly recommend you use the Semi-Auto GB mode, once locked the X calibration cannot shift unless the temperature of the electronics shift a lot (can only shift a few % points from dead cold), however if using Auto in some ground types you will only need to walk 20 meters in Auto and the conductive and saturation signals can throw the Calibration right out, this then has a flow on effect with the G balance which then tries its hardest to compensate but WILL fail.

In the conductive areas in the US (Nevada etc) the X signal is probably minimal and the Alkali the worst so the Auto mode should not be too badly affected by a bad X balance, best way to check is to pass the coil over a ferrite occasionally and see how loud the signal is, personally even though there is not much X present I would still be using Semi-Auto if for no other reason than it might give me a slight advantage over other operators.

My experiences in Arizona showed me there was plenty of X signal to be had in and around the Bradshaw mountains, even up at Rich hill there was plenty of ground that was variable (this was in the days before Smooth, GP3000 from memory) and I’m sure there would be plenty of X signal around. Mineralisation that forms gold that is then weathered has all the elements that can affect a metal detector no matter where in the world we work, if it didn’t then Americans would still be using VLF machines there would be no point to a PI. Case in point the new Garrett Axiom, obviously there is still a need for a PI in the US.

JP

https://www.minelab.com/__files/f/254884/KBA_26-1 GPZ 7000 Tips for Better Ground Balance.pdf

"In order to artificially add extra data for improved ground balance calibration, you can use a dust iron toroid, commonly referred to as an electronics 'ferrite'. The electronics industry uses these magnetic cores extensively in computers, televisions, and mobile phones. Ground balancing using a ferrite means that less soil needs to be covered during the initial ground balance period because the ferrite artificially adds very useful data to assist achieving an accurate ground balance."

Emphasis added. There is nothing in this document that implies that using the ferrite is mandatory, but simply that it can help aid, or speed up, the ground balance process.

Obviously detectors need to ground balance, but not one other Minelab detector needs a ferrite ring, so this is an issue regarding the GPZ, not detectors in general. As it was explained to me the need for a ferrite balance was for soils that lack enough naturally occurring ferrite. In that situation, the GPZ would not balance properly, or take longer than normal to get balanced. For soils with sufficient naturally occurring ferrite, no additional ferrite in the form of the ring is needed. Apparently Oz soils tend to lack this component, but in the U.S. naturally occurring ferrite is abundant. This is what I was told directly by Minelab, and if incorrect, then you'll have to argue with them, not me. I will say that in general, I rebel at being told what my personal experiences are, or are not, and most especially, how to react to things, how seriously to take them or not, etc.

That all said, I'll repeat what I said earlier:

"Can't swear it ever made a difference in my use in the U.S., yet I always used it as part of my tune up routine. Maybe it helped and I simply don't know it. Long story short, it can't hurt, might help, why not? You want to own the most expensive nugget hunter ever sold, best performance possible.... but that one little thing is just too much?"

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A few observations from an electronics guy, who has used these toroids.

There are two distinct 'types' of material used in these toroids: Powdered Iron, and Ferrite.

'Powdered iron' is ultra-fine iron dust, that is produced by chemical reaction, (rather than mechanical grinding etc ). There are some similar nickel-iron alloys ( eg. Permalloy) and other exotics like Sendust that can also be considered 'Powdered iron'.

'Ferrite' is non-metallic ( officially a ceramic ) that's essentially rust ( iron oxide ) with small quantities of metals like zinc, manganese blended into it. This is turned into fine powder by mechanical grinding, and then moulded.

They have quite different magnetic properties. Powdered irons have low magnetic permeability, (mu), typically varying from 1 to 100. Ferrites generally have higher mu, from 50 up to 15000.

Minelab specify a low-mu powdered-iron toroid, not ferrite, for detector balancing:
Quote:
"A ‘dust iron’ toroid suitable for the HF frequency band (e.g.1–30MHz with an initial permeability of between 6 and 10) has been carefully selected."

Regarding colour-coding:
It's primarily a powdered-iron thing, even then, different manufacturers have different coding, and there's plenty of different materials/blends that it's not worth trying to identify a toroid by colour. Magnetic testing will tell you much more.
Ferrites have no useful colour-codes, and are often unpainted, as they are naturally corrosion-resistant.

So if you're wanting to self-select a toroid for detector set-up, you want permeability, mu, of 6 -> 10, and a physical size that's vaguely the same as the ML suggested type, though it's not critical.

For reference, here's Amidon Corporations data sheet for ferrite and iron cores ( pdf )

http://www.amidoncorp.com/product_images/Amidon-Tech-Data-Flyer-v19.pdf
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1 hour ago, PimentoUK said:
A few observations from an electronics guy, who has used these toroids.

Minelab specify a low-mu powdered-iron toroid, not ferrite, for detector balancing:
Quote:
"A ‘dust iron’ toroid suitable for the HF frequency band (e.g.1–30MHz with an initial permeability of between 6 and 10) has been carefully selected."
 

From an electronics gal who has also used them, may I say thank you for your excellent write up, and rest assured, there are lots on here who loved is at much as I did and know all about the differences between mix 31 and mix 73... 🙂

The nice thing about this forum is that it's CHOCKER BLOCK full of some extremely intelligent people, like yourself, some of us just lay pretty low on the detailed tech conversation for fear of "deer in the head lighting" some/new members etc.... but you are for sure among friends here.

Another great site, with lots of product and information:

https://palomar-engineers.com

Jen

image.png

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ML themselves seem confused on the issue then.

Because if you grind the paint off the official Minelab ring, you will see it's actually black ceramic ferrite under the paint, not metallic powdered iron as they apparantly recommend. Unless the powdered iron look black also? In which case, the Doc's ring was some kind of pure iron then, it was shiny and metallic and extremely magnetic.

The two types of rings respond very differently on the 7000, the metallic iron rings will not balance out and sound like more like an iron target than ground noise. 

I found the thread where I showed the difference here. You can see the black powder on my hand from the official Minelab ring too.

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Ferrites are shinier and silver-grey colour. They are normally extremely hard, you can't abrade them; scratch them with a knife, you get a silver steel streak on the ferrite.

Powdered iron is duller and blacker, and is medium-hard. With effort, you can scrape off small bits, and strong abrasives like silicon-carbide paper will remove it.

So the ML ring is powdered-iron. The colour isn't very informative ... they might just have painted it black themselves to hide the manufacturers part marking.

The 'Doc' toroid seems typical of ferrite: shiny, hard. But ferrite is almost always electrically non-conductive, though I have read about some that will conduct ... I have no idea what type. 38 Ohms is surprisingly low. Again, color coding is hard to interpret .. yellow with one white face is typical of Type 26 ferrite blend.

Edit:
It is the very-high mu ferrites that are electrically-conductive ( mu over 5000 typically ), and I've just measured one example ( probably mu=15000) in my 'bits box', and it reads 200 Ohms across its diameter. That may be indicative of the 'Doc' ring material.
Jason: Do you have an inductance meter?
Wind 50 turns of enamelled copper wire on each toroid ( diameter 0.15 to 0.6mm, not important ), and see what an L meter gives. I guess the ML one will measure about 30 microhenry. The 'Doc' sample may be anything, up to 20 millihenry.
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12 hours ago, Steve Herschbach said:

https://www.minelab.com/__files/f/254884/KBA_26-1 GPZ 7000 Tips for Better Ground Balance.pdf

"In order to artificially add extra data for improved ground balance calibration, you can use a dust iron toroid, commonly referred to as an electronics 'ferrite'. The electronics industry uses these magnetic cores extensively in computers, televisions, and mobile phones. Ground balancing using a ferrite means that less soil needs to be covered during the initial ground balance period because the ferrite artificially adds very useful data to assist achieving an accurate ground balance."

Emphasis added. There is nothing in this document that implies that using the ferrite is mandatory, but simply that it can help aid, or speed up, the ground balance process.

Obviously detectors need to ground balance, but not one other Minelab detector needs a ferrite ring, so this is an issue regarding the GPZ, not detectors in general. As it was explained to me the need for a ferrite balance was for soils that lack enough naturally occurring ferrite. In that situation, the GPZ would not balance properly, or take longer than normal to get balanced. For soils with sufficient naturally occurring ferrite, no additional ferrite in the form of the ring is needed. Apparently Oz soils tend to lack this component, but in the U.S. naturally occurring ferrite is abundant. This is what I was told directly by Minelab, and if incorrect, then you'll have to argue with them, not me. I will say that in general, I rebel at being told what my personal experiences are, or are not, and most especially, how to react to things, how seriously to take them or not, etc.

That all said, I'll repeat what I said earlier:

"Can't swear it ever made a difference in my use in the U.S., yet I always used it as part of my tune up routine. Maybe it helped and I simply don't know it. Long story short, it can't hurt, might help, why not? You want to own the most expensive nugget hunter ever sold, best performance possible.... but that one little thing is just too much?"

Steve did I quote you at any stage? I’m not telling you to do anything, mandatory or otherwise. I am also not telling you about your personal experiences only my own, which in the case of the US was extremely limited.

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24 minutes ago, Jonathan Porter said:

Steve did I quote you at any stage? I’m not telling you to do anything, mandatory or otherwise. I am also not telling you about your personal experiences only my own, which in the case of the US was extremely limited. I’d appreciate the name of your contact at Minelab so I can take it up with them.

Steve pulled those words off the sheet JP so I don't think it's a quote.  All is great info though.

This is from the sheet: "An advanced ground balancing method for optimum performance In order to artificially add extra data for improved ground balance calibration, you can use a dust iron toroid, commonly referred to as an electronics 'ferrite'. The electronics industry uses these magnetic cores extensively in computers, televisions, and mobile phones. Ground balancing using a ferrite means that less soil needs to be covered during the initial ground balance period because the ferrite artificially adds very useful data to assist achieving an accurate ground balance. The easiest way to add this data during the initial ground balance, and and ideally, at all later ground balancings, is to place the ferrite on the soil surface and swing the coil over it several times in wide sweeps at the operating height of the coil, whilst ground balancing, so as to include data from both the soil and the ferrite."

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