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Iron Bias Fe Versus Fe2


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Note that the Iron Bias function is only available when the Equinox is operating in multifrequency. The setting will not be available in single frequency modes. Use the Accept/Reject button to toggle between FE and FE2 once you have accessed the function.

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Equinox Manual, page 52 (emphasis added):

All ferrous targets produce a combination of a ferrous and nonferrous response. Large ferrous targets can even present a stronger non-ferrous response. Also, a ferrous target adjacent to a nonferrous target can produce a similar response.

The Iron Bias Setting provides some control over the Target ID response. A lower Iron Bias setting will allow the natural response to dominate which means that the target is more likely to be classified as a non-ferrous target. A higher setting will increase the likelihood that the target is classified as iron.

In environments with dense iron trash, a higher Iron Bias is recommended in order to mask them. In areas where you do not want to miss any non-ferrous targets amongst iron trash, a lower setting is recommended. This will cause more ferrous targets to be detected and identified as desirable non-ferrous targets.

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Where iron bias gets iffy is on really deep iron/not iron targets and on really big iron targets (especially deeper ones) that will break through any attempt to discriminate them out with some major falsing being the result. I can get an on the surface railroad spike or large square nail to stop falsing on a setting of F2=7 to 9. However, any target relatively close to that spike will be almost completely masked.  Also, the deeper those big iron targets are the harder it is to get them to stop falsing which is why I raised the question about how deep should I expect the Equinox iron bias function to work effectively and on what sized targets.

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14 minutes ago, Jeff McClendon said:

how deep should I expect the Equinox iron bias function to work effectively and on what sized targets

Like most things I would expect that to be totally dependent on ground mineralization, and therefore highly variable. No matter what detector I use, my expectation is all functions break down with depth and any increase in mineralization. The question for me is most applicable to gold nuggets in mineralized ground, where my inherent distrust of ferrous filtering always comes to the fore.

I have seen countless ferrous signals turn out to be gold nuggets in high mineral ground. My fear is increasing the iron bias at all in such ground conditions all but insures this will occur. I will dig literally thousands of nails rather than risk seeing a large nugget at depth passed up as ferrous. A 10 ounce nugget will read ferrous right at the edge of detection depth, so size does not mean as much as signal strength. A small nugget in real bad ground can easily read ferrous, and adding enough depth to turn that big nugget signal into a faint reading risks having all that intervening soil create a ferrous masking effect.

In general I consider Iron Bias to be a last ditch function, left at zero unless I am forced to use it. By that I mean ready to walk away from a site due to false signals causing me to dig endless ferrous. In such situations it’s better to just crank the control up, and accept the losses for whatever they are. Better that than abandoning the location, which means no finds at all.

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26 minutes ago, Steve Herschbach said:

In general I consider Iron Bias to be a last ditch function, left at zero unless I am forced to use it. By that I mean ready to walk away from a site due to false signals causing me to dig endless ferrous. In such situations it’s better to just crank the control up, and accept the losses for whatever they are. Better that than abandoning the location, which means no finds at all.

I am posting this from a different discussion, my words.

 

I can elaborate on IB. Because the 1,2 and 5 peso coin rings in ferrous from -3 to -6 I run Iron bias of 4-5. This keeps these coins in check for falsing. 

My other saved program that I use for checking "iffy" signals has an Iron bias of zero. 

Anytime I go to my other program I ask myself, am I digging this target or not?  Out of all the times I been undecided and then checking with the other program. NOT ONCE have I found a target of worth.  

Now there is not a huge amount of targets that change my mind when I look with the second program, but still an accurate summary of actual events. 

The Equinox is a very powerful discriminator. One needs to trust the machine! 

 

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The thing is, the vast majority of detectors I have ever used like to call those rotted can sections non-ferrous. It is a rare detector that can tune the stuff out halfway well, and none that have a specialized variable control for the function besides the standard disc notches. I’m kind of anxious now to give the Equinox a try at a highly polluted site and see how it goes. Never a free lunch though. Cranking the setting up will help shut up lots of the flat ferrous, but also increase the masking. Then you are right back to square one, digging the ferrous to reveal the hidden treasures. 

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11 minutes ago, Steve Herschbach said:

Never a free lunch though. Cranking the setting up will help shut up lots of the flat ferrous, but also increase the masking. Then you are right back to square one, digging the ferrous to reveal the hidden treasures. 

Well for all reading, I only hunt salt beaches. So my results are geared toward this venue. I also run a recovery of "6" in my go to program. When I go to my double check program not only is the IB "0" but the recovery is "4".  I hunt a unique situation with ferrous coins being a very high number of daily targets. But yet my yield of gold seems to be unaffected with my settings. 

If I ever do find a target of value with the second program it will be a significant finding. 

On average I would estimate I do 20 or so secondary program looks a day.  

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6 hours ago, Steve Herschbach said:

The part I do not show? There are good items that will do the same, and I need to try and find one. In theory there is a good item that will give a false ferrous if this setting is too high. Otherwise we would not need the control. Just set it to max and forget. So the real question here that I think remains is not about the ferrous. The control will clearly help with making ferrous items read ferrous. But what about the reverse? What non-ferrous items will be revealed by leaving this control at a low setting?

 

44 minutes ago, Steve Herschbach said:

Like most things I would expect that to be totally dependent on ground mineralization, and therefore highly variable. No matter what detector I use, my expectation is all functions break down with depth and any increase in mineralization.

IMO you can combine these two thoughts.  Here's my hyphothesis.  Iron bias doesn't affect surface non-ferrous targets, but as that item goes deeper the falsing (non-ferrous item sounding ferrous) starts to occur.  The higher the iron bias setting the shallower that crossover occurs (for a given ground mineralization). 

There may be competition between the target 'disappearing' completely due to being too far from the coil (i.e. too deep) and the target (not so deep as to be lost but) sounding completely ferrous.

Thus for deep non-ferrous you want the iron bias setting minimized.  That's where it matters.

I emphasize this is merely an hypothesis.  I've not proven it (yet).

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Steve's test results are very interesting.  I never knew that F2 could be that effective because I have been afraid to crank it that high out of fear of masking.

As far as a no free lunch is concerned, my main concern has always been masking.  IB tends to counter the target separation effects of higher recovery speeds effectively mitigating the setting.  Put another way, you might have to crank recovery speed higher to overcome the target masking effects of IB, but there is probably a point of diminishing where depth becomes limited and exacerbated by the other downside of IB, where deeper non-ferrous on the edge of detection look ferrous.  This is similar to the masking effect but a little different.  As with most of these settings, the key is finding the sweet spot intermediate settings of IB and recovery speec that provides the best balance of these tradeoffs. That, of course, is dependent on search mode, ground conditions (e.g., mineralization), ferrous and non-ferrous junk density, and the primary targets of interest (gold vs. jewelry vs. coins vs. relics, mid-conductors vs. high conductors...) and their depth.  I guess that takes me back to my preferred middle-of-the-road IB setting of F2 = 4 to 6 as a good starting point.

 

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