Ferrite Ring 8 Years Later

[Steve Herschbach]

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?"

[PimentoUK]

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

[jasong]

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.

[PimentoUK]

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.

[Jonathan Porter]

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.

[Gerry in Idaho]

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."

[jasong]

1 hour ago, PimentoUK said:

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.

Heard, but I still don't think the ML ring is powdered iron. At least, not if that's what the other ring is, which it has to be because it rusts and is much more dense and highly magnetic. The ML ring is painted yellow, not black. The black is the ferrite itself after I sanded the yellow paint off. Density, magnetism, conductivity all indicate it's ferrite when compared to the other ring. Looks, walks, quacks like a duck...

But I'll try to find those rings again and throw them on the XRF just to see for certain. I'll post back here if I can find them, all my unused stuff is packed into boxes right since I'm moving so I'm going to have to do some digging.

It'd be good to know, whatever the case may be. What I can say for certain is this: the ML ring balances out on the 7000. The other ring does not, it sounds like an iron target. So they are definitely two different materials and one probably isn't doing the job it was intended to do. 

[jasong]

Check out that link I posted on the other page. This was a ferrite I bought 3 years ago. I told Rob about when I bought it.

If the ones they are selling now aren't shiny metal iron underneath the paint, then the ring they are selling changed since I bought mine. What you see in that post is exactly what I got off Ebay at the time though.

*Actually, the more I think about it, the more I think the Doc ring (at least, at first, maybe things changed now) was just a solid iron ring some manufacturer sold as "ferrite" or something. It was probably sourced from China, and I know a lot of times I get inexpensive Chinese components, they aren't actually what they say they are - they are just whatever is cheapest to make that performance "roughly equivalent". If the ML ring is actually powdered iron and not ferrite, that's the only logical explanation, and also explains why the other ring rusted after sanding paint off it. 

[Steve Herschbach]

On 8/9/2022 at 1:34 PM, Jonathan Porter said:

X signal is no joke on the 7000 so I’m surprised by all the head in the sand humour surrounding it’s use on here. Yeah I get the humour, Octopus dance, Ferrit, ritualised activities around the fragile yellow round thing etc, but in reality it is an important aspect to ZVT and should be taken very seriously.

Just a bunch of people with heads in the sand, yup. My comment was simply about how serious all this is, when in my world it’s not serious at all, and I think people making fun or jest over it, not worth getting all worked up over. But that’s just me.

Been ages since I was discussing GPZ with any engineers, and not inclined to spend any more time on this.