Minelab Equinox Iron Bias explained

The Equinox detector is the newest technology released by Minelab. It has some new features never offered before. So it’s only natural that there is a bit of confusion about what it does and how to adjust it. So, what is the Equinox iron bias? To reduce it to a simple answer; if you are trying to unmask coins that are hidden by the presence of nearby iron, then a lower iron bias is what you want. That’s the short answer, here’s the long one…

A detailed answer

Let’s define, for the purposes of discussion, any situation in the ground where you are getting a mix of low tones and high tones as a mixed target. Obviously, one type of “mixed target” arises from a coin lying near a nail. However, some mixed target responses occur simply because you have a nail (low tone) that is giving you some high tone falsing. In other words, not two separate targets in the ground. Instead, one target (the nail) that confuses the machine a bit. Presenting some high-conductive traits within the received signal being seen by the coil, along with the more dominant, low-conductive iron response.  Obviously the degree of this falsing depends upon sensitivity of the machine, the frequency being utilized, and other factors.

In a perfect world, we’d like to have a super-sensitive machine, yet one that does not give false signals on nails. Instead, it correctly IDs them entirely as iron and only gives us the high-tone/low-tone mix when there are actually two co-located targets. But, we don’t have that ability yet. So, this is where “iron bias” enters the picture, being a tool that can help a bit.

Avoiding iron falses

Skewing the mixed target towards iron

If all we want to do is eliminate falses, we can run iron bias up high. What that is  telling the machine is “on mixed targets, instead of letting me hear iron tones AND occasional high tones, eliminate the high tones.” i.e. ‘bias’ the response toward all iron tones/IDs. This can be good, in that you won’t be bogged down by the “jumpiness” of the machine.  You can focus only on the clear, solid, repeatable high-toning targets while ignoring most of the nails (as those nails will now ID more solidly as low-tone iron). However, the obvious downside to this is that you will miss some partially masked coins because you have told the machine (with your iron bias setting) to de-emphasize any high-conductive response that is occurring near primarily iron targets.

Finding the hidden coins

skewing mixed target towards conductive

On the other hand, if we want maximum unmasking ability, we can run iron bias down low, and in that case what we are telling the machine is “anytime you are seeing some high-conductive response near an iron target, EMPHASIZE those high tones for me; allow them to bleed through.” In other words, “bias” the machine toward an emphasis on high tones, in any mixed target scenario.

The benefit of setting up the machine this way is, obviously, if your mixed target happens to be a coin next to a nail, you will be allowing the coin response part of the signal to be emphasized and thus making it more likely you HEAR that co-located coin. Therefore, low iron bias settings allow you a much better chance of digging partially masked coins. However, the obvious downside is, you will dig more nails, as again, high-tone nail falses are also a “mixed target,” and your low iron bias setting is telling the machine “emphasize” THOSE high tones, also, just the same as it would any high-tones associated with a partially masked coin.

Everything is a trade-off

So, the answer to the question of “where to set the bias” depends upon what you are trying to do, what your goal is at that time. Do you want to hunt “quiet,” and dig only the solid coin hits? Or are you hoping to maximize your unmasking capability in a heavily hunted, nail-infested site?
After all that long-winded response, the point is, running iron bias low gives you the best chance of digging any partially masked coins in your very trashy site, but it will come with the downside that you will likely dig more “falsey” nails.

false or mixed?

Thanks to Steve G. for the help explaining this concept.

You can read further articles covers use of the “Recovery Speed” setting and “Ground Balance” settings.