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Why no iron bias control in single frequency?

Ditto on using a small coil. Compared to something like an 11" coil, a small coil in trashy sites will outperform the 11" on many levels.

Since getting a 6" coil, I rarely ever use the 11".
 
I don't have my NOX 800 anymore to test this, but can someone take a small gold chain and a piece of wire for a test? I want to see "iron bias" used to ignore the piece of iron and sound off on the small gold chain. That would be not just discriminating.

That would be interesting.

Although for a small gold chain, using a high single SF, or a low conductor weighted SMF, will likely be important.
 
That would be interesting.

Although for a small gold chain, using a high single SF, or a low conductor weighted SMF, will likely be important.

Not saying it can't be done, just saying to convince me iron bias is anything more than a fine tune discrimination for the expanded lower end.

The example I'd like to see is how a piece of iron wire will give a VDI of say 04 and an iron grunt. IF, iron bias is more than just a discriminator adjustment, then a small gold chain, that also would read a VDI of 04, would not give a grunt but a tone indicating a conductive target in the iron range. That would tell me it truly could find non-conductive targets in with ferrous. If not, it is just discrimination adjustment.
 
Sorry Detector, I read through your post too quickly, and didn't realize that you were still confusing iron bias with iron discrimination :)

Iron bias needs opposing data points to work. If there are no opposing data points, then iron bias can't be "biased" to one data point or another, because only one data point exists in your example.

In your example, the gold chain reading as iron 4, will be exactly the same to the detector as the iron wire reading as iron 4. There is nothing for the detector to be biased toward, or against. In other words, iron bias is irrelevant, and doesn't apply in your example.
 
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Sorry Detector, I read through your post too quickly, and didn't realize that you were still (mistaking ;)) iron bias with iron discrimination.

Iron bias needs opposing data points to work. If there are no opposing data points, then iron bias can't be "biased" to one data point or another, because only one data point exists in your example.

In your example, the gold chain reading as iron 4, will be exactly the same to the detector as the iron wire reading as iron 4. There is nothing for the detector to be biased toward, or against. In other words, iron bias is irrelevant, and doesn't apply in your example.

Thanks, and that was my point. A detector, talking Induction Balance or VLF, receives feedback from a piece of metal. If that detector assigns a value of 04 to the returning frequency, if it treats it the same whether it is ferrous or non-ferrous, then I say iron bias is simply adjusting the iron discrimination. If it gives an iron grunt on 04 ferrous, and a high tone on an 04 that is conductive, then iron bias is not just a hyped-up discrimination.
 
I think some folks are still confusing iron bias not just with iron discrimination, but also with unmasking. To put it simply, Iron Bias (and I assume, Iron Filter on the Legend) allows the user a way to influence how the machine responds to mixed-signal targets that might cause a “falsing” ferrous item to indicate in the non-ferrous range, without changing how the machine responds to solid, non-ferrous targets. Discrimination and/or tone break adjusts how the machine responds to different conductivity characteristics across the board…”fine tuning” a tone break or discrimination means any item assigned a particular conductivity value looks and sounds the same on the machine. It's an important difference.

To use the numbers from Detector’s requested example, iron bias won’t give an iron grunt on a +4 ferrous, and a high tone on a +4 non-ferrous – that’s just not how it works. Instead, when set properly, iron bias will turn a target into a -5 if it’s ferrous, when it might otherwise read +4. Meanwhile, a +4 non-ferrous target will remain +4. That’s what iron bias accomplishes, and it needs more than one simultaneous data point from multifrequency to make it happen… it’s impossible on a single frequency machine or mode because a +4 hit is a +4 hit - there’s nothing to compare it to. The video that I made below shows this effect directly. The best I have laying around the house that has matching VDI numbers at low iron bias is a rusty iron horse tack ring and a small gold pin. For those who don’t watch videos, it shows both targets individually reading at 12-13 VDI at iron bias setting F2 0. At a slightly increased iron bias of F2 3, the horse tack ring reads -2, while the gold pin continues to read 12-13…no other settings changed beyond iron bias. Don’t get too caught up in the idea that the horse tack ring is a large target, the same effect can be demonstrated with a smaller iron target, as long as it is dense enough that it’s conductivity “fools” the detector into assigning a higher VDI reading. Honestly, I don’t think you can demonstrate iron bias on “a small iron wire” with a non-ferrous target in an air test as Detector requested, because the detector won’t get fooled by the small wire on the surface…a small wire on the surface doesn’t generate enough conductivity to alter the detector’s field and trigger “falsing”, or a high VDI (see the Iffy Signal video posted earlier in the thread - the nail stays as iron, the detector isn't fooled). Bury that same nail in the dirt several inches and let it marinate in the ground for awhile, and yes, a detector will start to false on the tips, and iron bias will become useful in certain situations again.

I consider true unmasking to be a situation where a detector can be set up to see two targets when it would otherwise see only one. Iron bias is not intended to be an unmasker, although it can sometimes look that way (again, Iffy Signal’s video posted by Digalicious earlier in the thread is a good example). Unmasking is what recovery speed (or reactivity for Deus), slower sweep speeds, and/or smaller coils, etc, are for. If a ferrous and non-ferrous target are too close together and recovery speed is too low, a target is more likely to get missed. Iron bias can exacerbate this effect, of course - if iron bias is set too high, and the machine sees the two targets as one co-mingled target signal, a high iron bias set by the user will mark the signal as ferrous, and you’ll never hear the high tone. This is exactly what the earlier Iffy Signal’s video is showing, and I can demonstrate a very similar test with the Equinox 800 (frankly, the Legend may perform slightly better based on my own tests compared to his video). While watching that video, you can easily convince yourself that the change in Iron Filter “unmasked” the coin from the nail – that the Legend was seeing two individual targets and that as the iron bias was increased, the detector “erased” the nail like a magic wand and left the coin, but that’s not really what is happening. I make the case that the Legend was seeing the nail and dime as a co-mingled single target, presenting both ferrous and non-ferrous levels of conductivity as the target was sampled in multifrequency mode. With the Iron Filter set at 8, the detector was doing as the operator told it to do – “call that kind of signal iron”. As he changed the Iron Filter down toward the lower numbers, again, the detector was doing as it was told, and assigning the mixed multifrequency signals non-ferrous VDI numbers and tones instead.

But again, Iron Bias (or Iron Filter) is not a magic wand, it’s just a tool. If you combine what I show in my video with what you see in Iffy Signal’s video, you can see the obvious downside to iron bias. In both of our videos, we have the benefit of seeing what the targets are…a nail next to a coin, a chunky piece of iron, and a piece of gold. But in the real world, you still have no real idea what you might be digging when the machine alerts you with a solid non-ferrous signal…it might be a masked coin, it might be gold, it might still be balled up aluminum. But hopefully, if the iron bias is set up properly, the target is much less likely to be a falsing iron nail.

 
That makes it a little clearer AirmetTango, thanks.

A second look tells me what I needed to see. I believe iron bias and discrimination are NOT the same.

I figured Monte knew what he was talking about, but your video showed me what I needed to see. Sometimes a video is worth a thousand words indeed LOL.
 
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That makes it a little clearer AirmetTango, thanks….

Cool, glad it helped out Detector! Iron bias (or Iron Filter) isn’t an intuitive setting, and the feature has several nuances that definitely takes time and practice to wrap your head around. Heck, I enjoyed reading the thread, thinking about the questions, doing the video, and the write up because it helped me to solidify my own understanding of iron bias and how to explain it. :cool3:
 
Cool, glad it helped out Detector! Iron bias (or Iron Filter) isn’t an intuitive setting, and the feature has several nuances that definitely takes time and practice to wrap your head around. Heck, I enjoyed reading the thread, thinking about the questions, doing the video, and the write up because it helped me to solidify my own understanding of iron bias and how to explain it. :cool3:

Most here know when I have it in my mind what I believe to be fact I dig in like an Alabama tick, but I can admit when I'm wrong. The hard part is convincing me I'm wrong LOL. I read a lot of info trying to explain how Iron Bias works, but having done a lot of videos myself, it just took your video to show me what I needed to see to know I was wrong.
 
For those that want the best way to sniff out the coins from iron, then an iron bias control is a critical component for doing so. However, choosing the correct frequency, or frequency range, is also very important. You would want to use an SMF that is weighted toward the high frequencies, or if SMF isn't possible for some reason, then use a single frequency of around 15 khz or higher.
 
Dealing with all sorts of conditions can be a challenge yet for someone using a detector because when we get into a mix of different metals in close orientation we end up with multiple signals or a blended signal if there are 2 targets close together. Also, we have to remember that we have problem iron trash. Some iron trash is easily discriminated and it's not a problem, it's when we get into the more conductive iron which is often Man-made or man-shaped then it can bring us some difficulties.

A good example would be the old pry-off Bottle Caps. A man-made, ferrous-based target that everyone on the past four or five years with the most modern detectors wants to be able to deal with. Equinox, Deus siblings and Legend, for example. And we hear of the Iron Bias, which is not Discrimination, as being an adjustment to help process that ferrous resppnse to help clean up the response so that it can be give the user better information about the bad trash as well as maybe help unmask a closely-located higher-conductive target.

But we hear that IB only works on a SMF unit and especially with a "more weighted" higher frequency, not a SF. Really? How about two or three models I have been using since June of '94 that have an adjustment function to help classify a problem ferrous target, the annoying Bottle Cap? AND it is Single Frequency AND a lower Frequency!

The main unit with BCR I have used for over twenty-eight years is the White's XLT, the operating Frequency is 6.6 kHz, and the problem ferrous trash adjuster is called BCR or Bottle Cap Reject. It is not Discrimination but basically an eRly version we could call Iron Bias which controls that ferrous response do that we might audibly reject the problem target which has a more "trashy" audio signature.

Just a little food for thought suggested by someone who has over a half-century of avid experience and applies what he has, and will, learn. I still use a wonderful XLT for select sites, and the BCR/IB control is set where it works for me in those environments.

Monte
 
But we hear that IB only works on a SMF unit and especially with a "more weighted" higher frequency, not a SF. Really? How about two or three models I have been using since June of '94 that have an adjustment function to help classify a problem ferrous target, the annoying Bottle Cap? AND it is Single Frequency AND a lower Frequency!

You're right, Monte - I should have been more clear in my discussions above. Almost every manufacturer has implemented their own version of a feature that's intended to help deal with tricky iron beyond discrimination alone on at least some of their detectors...the concept is definitely not new. But they don't all accomplish that in the same way. That's why I said this in my original post in the thread:

So to answer your original question, I believe Iron Bias is only available in multi on the Equinox while Silencer is available in all modes on the Deus 2 because the two features are apples and oranges.

The OP's post was focused on the Deus 2, Legend, and Equinox, so I initially addressed those three. But when the follow up questions drifted to iron bias specifically, I assumed the Equinox feature was meant and I went into more detail about it since it's the detector I use exclusively right now. So when I'm talking about multifrequency being required for Iron Bias in my posts above, I'm talking specifically about the proprietary Minelab feature of Iron Bias (capital letters) and how it works. It appears the Nokta Makro version, called Iron Filter on the Legend, works in a similar manner. I know nothing about Silencer on the Deus "siblings", but since it does indeed work in single frequency like the other machines you mentioned, I'm willing to guarantee it's a different animal with completely different sets of advantages and disadvantages. The semantics start to get confusing, because I've seen folks elsewhere talk about "iron bias" (lower case letters) as a catch-all phrase for various brand's features (like "Kleenex" for tissues). But while the end result may seem similar - tricky iron gets better identified in some way - the different individual features sometimes get there using completely different methods. I like your phraseology: "adjustment function to help classify a problem ferrous target". Covers the various tools (Iron Bias, Iron Filter, Silencer, Iron Audio, etc.) from different manufacturers without borrowing a trade name in the process! Kind of long to say, though ;)
 
For those that want the best way to sniff out the coins from iron, then an iron bias control is a critical component for doing so. However, choosing the correct frequency, or frequency range, is also very important. You would want to use an SMF that is weighted toward the high frequencies...

Agreed - I've experimented a little bit more and realized the frequency weighting in multifrequency is very important to the effectiveness of iron bias on the Equinox. While attempting to duplicate the iron nail/dime test from the Iffy Signals video you posted earlier in the thread, my Equinox didn't appear to perform nearly as well as his Legend in his video - at the lowest IB setting there was almost no hint of a non-ferrous signal on the Equinox. But then I realized I was doing all of the testing in the Equinox's Park 1 mode. When I shifted into Park 2, the non-ferrous signal popped out much more prominently at low IB settings, and the ID wasn't dragged down very far, pulling a 18-20 ID on the blended target. The difference is surely the higher frequency weighting of Park 2 relative to Park 1.
 
AT,

I see so many posts and videos of users doing a similar test, or hunting in ferrous infested sites, but not using the correct SMF mode. Then alas, they erroneously proclaim to all, that the detector "has a problem". As such, I was pleased to see that Iffy was using the correct low weighted (M2) SMF mode to unmask high conductors from ferrous trash.
 
Could shape of iron ( not associated with bottle cap behavior) drive Equinox’s behavior using either FE or F2 iron bias?
I can’t say anything more right now. NDA

I did watch your video, and to answer the question in your post, yes, of course the shape of the ferrous item will drive the Equinox’s response when either FE or F2 is used, because they are designed to be different. In fact, as many of us know, not only will shape affect the response, but so will composition, size (different than overall shape), and orientation. In your video, if you were to do the test again with the nail oriented horizontally rather than vertically, you’ll get another set of numbers from both FE and F2. This doesn’t just happen with ferrous, it can also happen with non-ferrous…for example, a buried silver dime on edge ID’s differently than one laying flat. And yes, since iron bias is always on to some degree in multifrequency, the actual ID displayed could be altered at least somewhat, especially if the ground is mineralized or other ferrous itty-bitties are under the coil. Because that’s what Iron Bias does - it changes the way the machine responds to mixed signals. So different Iron Bias settings create different responses for different targets. No surprises.

For the bottle cap in your video, there’s no surprise there either…the manual specifically states that F2 was designed to better deal with “a wider range of ferrous targets, including some types of crown cap bottle tops that Iron Bias FE is less effective for” (see image below). I would guess that the rusty cap you used was a blended target - an alloy - not pure iron like the nail. That’s why you see the drastic difference not just between FE 9 and F2 9 in your test, but you’d also see a big difference between F2 9 and F2 0…because that’s what F2 was intended to do - by the manufacturers own words, F2 is aimed to help solve issues created by trickier bottle caps. Remember, there’s nothing special about iron per se - all the Equinox sees is different responses based on the overall conductivity of a target. Large pure ferrous objects can create a non-ferrous response as well (also specifically mentioned on the same Equinox manual page), which is why the horse tack ring (nearly pure iron) was solid non-ferrous in my video at low iron bias settings.

Sure, your last sentence in the video could be accurate - F2 is probably not just a “fine tuning” of FE. The two filters may be processing the multifrequency signals completely differently. We, as non-Minelab engineers, have no way to know for sure. I won’t say more because it would be pure speculation. Non-NDA.
 

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Large pure ferrous objects can create a non-ferrous response as well (also specifically mentioned on the same Equinox manual page)

That raises another issue that many end users aren't aware of. That is "Iron wrap around". That of course produces the typical and and erroneous, "This detector isn't very good because some iron ID's really high".

When newbies ask me how to notch for coin cherry picking, I also include the instructions to notch out the extreme high end of the conductivity scale.
 
About every three months somebody poses this same question and eventually I post this stuff that is right off of Minelab's website in an article explaining what Multi IQ is basically. The necessity for an iron bias function is the direct result of this explanation as long as one is using Equinox in its Multi setting.

No NDA restrictions necessary. This is published, public information down below.

People can postulate, give opinions, argue, disagree and dissect this subject all they want. The reason for iron bias is right here in black and white even though the term Iron Bias is not mentioned. So is the reason for the existence of Multi IQ and the Equinox. It also explains how Multi IQ is very different from BBS and FBS in this same article.

Australia along with many other places on this planet is plagued with high iron mineralization. So are many saltwater beaches. This is why the Equinox and Multi IQ exist, plain and simple.

Many early dissenters said that the Legend is just a knock off (and a poor one to boot) of the Equinox. Let's just say the Legend is very Equinox like. If it's multi frequency tech is anything like that on the Equinox then the Legend needing some kind of iron bias function is also made clear by these next sentences.

Why does Deus 2 have a bottle cap reject function in most of its multi frequency modes.........? Bottle cap reject is not available in Deus 2 Mono (silencer only), Deus 2 Goldfield (disc IAR) and Deus 2 Relic (disc IAR).
-------------------------------------------------------

Multi-IQ is derived from:
Simultaneous Multi-Frequency In-phase and Quadrature Synchronous Demodulation.

We can go to a statement from Dr Philip Wahrlich, our principal technology physicist, about a key difference of Multi-IQ compared to the demodulation taking place in conventional single frequency VLF detectors:

“Within the Multi-IQ engine, the receiver is both phase-locked and amplitude-normalized to the transmitted magnetic field – rather than the electrical voltage driving the transmitted field. This field can be altered by the mineralization in the soil (in both phase and amplitude), so if the receiver was only phased-locked to the driving voltage, this would result in inaccurate target IDs and a higher audible noise level. Locking the receiver to the actual transmitted field, across all frequencies simultaneously (by measuring the current through the coil) solves these issues, creating a very sensitive AND stable detector”

Precisely measuring these extremely small current variations is quite remarkable if you consider the levels involved. It’s actually parts per billion, or nanoamp signals, we are talking about here!

With Multi-IQ, we can derive much greater target ID accuracy and increased detecting performance, especially in ‘difficult’ ground. In ‘mild’ ground, single frequency may perform adequately, BUT depth and stable ID’s will be limited by ground noise; whereas the Multi-IQ simultaneous multi-frequency will achieve maximum depth with a very stable target signal. In ‘strong’ ground, single frequency will not be able to effectively separate the target signal, giving decreased results; whereas Multi-IQ will still detect at depth, losing a minimal amount of target accuracy.

Dr. Wahrlich continues:

“For each frequency the detector transmits and receives there are two signals which can be extracted which we refer to as I and Q. The Q signal is most sensitive to targets, while the I signal is most sensitive to iron content. Traditional single-frequency metal detectors use the Q signal to detect targets, and then use the ratio of the I and Q signals to assess the characteristics of the target and assign a target ID. The problem with this approach is that the I signal is sensitive to the iron content of the soil. The target ID is always perturbed by the response from the soil, and as the signal from the target gets weaker, this perturbation becomes substantial. With some simplification here for brevity, if a detector transmits and receives on more than one frequency, it can ignore the soil sensitive I signals, and instead look at the multiple Q signals it receives in order to determine a target ID. That way, even for weak targets or highly mineralized soils, the target ID is far less perturbed by the response from the soil.This leads to very precise target IDs, both in mineralized soils and for targets at depth.”

-----------------------------------------------

So Iron Bias on the Equinox (and maybe the Legend) is a tool that if used, allows the detector user to decide if any and how much of the I signal will be processed and added into the calculation of the eventual multiple frequency averaged target ID. If one uses iron bias on its most minimal settings, many iron and mixed alloy targets will false a lot in the mid to upper non-ferrous range. Use too much iron bias and the I signals from actual iron targets and from the ground can mask nearby non-ferrous objects.

Testing objects in mid air, on styrofoam and on concrete in my opinion takes the ground itself out of the equation and can skew results with detectors with this kind of technology.

Single frequency detectors take the I signals into account normally in the background as explained above. Deus, Orx, Deus 2 mono and a few other single frequency detectors have had additional iron filtering as an option.
 
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