Book Excerpt: "Iron Bias"
(Settings X 6 + long press, “+” or “-“ to adjust, “Detect” to exit).
The need for an Iron Bias setting on the Equinox derives from the operating characteristic of a high gain detector. While the Equinox’s sophisticated electronics act to inhibit inconsistent responses like iron, at the same time because there is so much Sensitivity going down into the ground there is still the possibility of iron falseing taking place. This involves iron objects that have very unusual properties such as a spike nail upended, or something large enough to mimic a non-ferrous response by overwhelming the machine’s circuits and coming in at the top of the discriminate range (termed “wraparound”) While these are usually recognisable by target testing (cross sweep for one), at the same time there is a need for a control that regulates the level of consistency in a target which is assigned the audio (rougher or broken tone) of iron. This feature is also useful to relic hunters or anyone wanting to hunt for coins in dense iron. You have the choice of trying to knock the iron out by way of the Equinox’s software, or opening up the machine to get cleaner, fuller responses on iron in order to hear what’s mixed in with it.
In effect, “Iron Bias” is a filter. Whereas the ground’s signal represents a large, unstable, response, a good target can be seen as a small, narrow and consistent response. “Iron Bias acts to mediate the “line” where this distinction is made. This doesn’t just include iron—but any object which contains multiple metals. So “Iron Bias” can be used to change responses from bottlecaps, corroded coins—anything that’s not “clean” metal such as silver, copper aluminum or gold. It’s worth noting though that with some targets that are comprised of both iron and non-ferrous metal, “Iron Bias” may act to “clean up” the signal—making it sound better. This is similar to the way that many rusted targets will sound better after several passes of a BBS detector (Sovereign / Excalibur) coil. The machine’s built-in bias is removing the inconsistent parts of the signal. Conversely, a lower setting can emphasise the alloying of an unwanted target--effectively “breaking it up.”
It’s worth noting though that because all metal in the ground “mixes” with it’s signal (corroded or not), using high levels of “Iron Bias” acts to reduce detection of all targets.
Understanding how “Iron Bias” works is an important lesson in how detectors work. In effect, they don’t just “punch down” though the ground to detect a metal target. Instead, what a detector does is to assess both the ground and any metal that’s in it and then separate the two—based upon this consistent / inconsistent scale. This is the scale that an “Iron Bias” control operates on.
“Iron Bias” can also be used a tool to moderate the effects of “black sand” by changing the machine’s response to the large, scattered inconsistent response it produces and promoting any “clean” metal targets that are mixed in with it. It also has the potential to stabilize the detector in “black sand” by reducing the Sensitivity to this erratic signal. This may require a higher or lower setting depending on the conditions.
When many hunters want to get the maximum depth with the Equinox, they take the “Iron Bias” right down to “1” or “2.” With this setting it’s generally agreed that frequent “Ground Balancing” of the machine helps to reduce the response to iron.
The “trade-off” here though is that you will still be “fooled” by more iron false signals.
From: "the Minelab Equinox: From Beginner to Advanced"
by Clive James Clynick
(Settings X 6 + long press, “+” or “-“ to adjust, “Detect” to exit).
The need for an Iron Bias setting on the Equinox derives from the operating characteristic of a high gain detector. While the Equinox’s sophisticated electronics act to inhibit inconsistent responses like iron, at the same time because there is so much Sensitivity going down into the ground there is still the possibility of iron falseing taking place. This involves iron objects that have very unusual properties such as a spike nail upended, or something large enough to mimic a non-ferrous response by overwhelming the machine’s circuits and coming in at the top of the discriminate range (termed “wraparound”) While these are usually recognisable by target testing (cross sweep for one), at the same time there is a need for a control that regulates the level of consistency in a target which is assigned the audio (rougher or broken tone) of iron. This feature is also useful to relic hunters or anyone wanting to hunt for coins in dense iron. You have the choice of trying to knock the iron out by way of the Equinox’s software, or opening up the machine to get cleaner, fuller responses on iron in order to hear what’s mixed in with it.
In effect, “Iron Bias” is a filter. Whereas the ground’s signal represents a large, unstable, response, a good target can be seen as a small, narrow and consistent response. “Iron Bias acts to mediate the “line” where this distinction is made. This doesn’t just include iron—but any object which contains multiple metals. So “Iron Bias” can be used to change responses from bottlecaps, corroded coins—anything that’s not “clean” metal such as silver, copper aluminum or gold. It’s worth noting though that with some targets that are comprised of both iron and non-ferrous metal, “Iron Bias” may act to “clean up” the signal—making it sound better. This is similar to the way that many rusted targets will sound better after several passes of a BBS detector (Sovereign / Excalibur) coil. The machine’s built-in bias is removing the inconsistent parts of the signal. Conversely, a lower setting can emphasise the alloying of an unwanted target--effectively “breaking it up.”
It’s worth noting though that because all metal in the ground “mixes” with it’s signal (corroded or not), using high levels of “Iron Bias” acts to reduce detection of all targets.
Understanding how “Iron Bias” works is an important lesson in how detectors work. In effect, they don’t just “punch down” though the ground to detect a metal target. Instead, what a detector does is to assess both the ground and any metal that’s in it and then separate the two—based upon this consistent / inconsistent scale. This is the scale that an “Iron Bias” control operates on.
“Iron Bias” can also be used a tool to moderate the effects of “black sand” by changing the machine’s response to the large, scattered inconsistent response it produces and promoting any “clean” metal targets that are mixed in with it. It also has the potential to stabilize the detector in “black sand” by reducing the Sensitivity to this erratic signal. This may require a higher or lower setting depending on the conditions.
When many hunters want to get the maximum depth with the Equinox, they take the “Iron Bias” right down to “1” or “2.” With this setting it’s generally agreed that frequent “Ground Balancing” of the machine helps to reduce the response to iron.
The “trade-off” here though is that you will still be “fooled” by more iron false signals.
From: "the Minelab Equinox: From Beginner to Advanced"
by Clive James Clynick
