What is iron bias function on a detector? does other detectors have iron bias that goes by another name? It seems that the iron bias on the Nox may be the main reason people buy the Nox.
Yes, other detectors have settings that are roughly equivalent to the Minelab Equinox's Iron Bias. I believe that the "Iron Filter" setting on the Nokta Makro Legend, and maybe "silencer" on the XP Deus are the same idea, just maybe with slightly different proprietary methods to achieve the results. No, I wouldn't necessarily say that the iron bias is the main
reason why people would buy an Equinox - I would probably rank simultaneous multifrequency, single frequency options, and excellent overall settings flexibility, etc higher than iron bias - but others might disagree.
Equinox's Iron Bias uses the multifrequency mode to get several simultaneous ferrous/non-ferrous data points from two different frequencies to more precisely differentiate how "iffy" a target is in terms of ferrous/non-ferrous content before routing that signal through the iron bias filter, which ultimately determines what kind of tones ultimately reach your ears. The function of iron bias setting is to allow the user a way to influence how the machine responds to targets that might otherwise cause a "falsing" ferrous item to indicate in the non-ferrous range in both tone and VDI, without changing how the machine responds to solid, non-ferrous targets.
To put it simply, when set properly, iron bias can allow the user to more easily differentiate between a buried iron object versus a desirable target. Here's a demonstration I created several months ago showing how iron bias can be used to differentiate between an iron horse tack ring and a gold lapel pin that otherwise rung up identically:
A common misconception is that iron bias is an "unmasker" - that's not what iron bias is intended to do. Unmasking is a job for higher recovery speeds, slower sweep speed, smaller coils, etc, not
iron bias. Iron bias does not provide separation between two individual targets - instead, it's intended to sniff out single targets that would otherwise fool the detector through falsing.