Equinox 900 Multi Frequency And Rusting Old Iron

[HardPack]

I have been attempting to getting my ears wrapped around the Equinox 900 “multi-frequency” using modified search modes Field #1 and Field #2. I changed both field search modes to 5-tone, recovery “1”, iron bias “0”, reference threshold volume  “11”, multi-freq.

The practice search location is an old ranch, the ranchers grew feed for the stock plus there is an abandoned railroad track. The train transported to and from the local quartz mines and lumber mills. The base rock is granitic and the soil is clay. (The east belt of the mode is within a mile to the east, in some of the mines the quartz stringers occur in granitic rock.)

The ground balances at  “40”, originally I ground balanced by pumping the coil but found it best to use ground tracking. The practice targets are widely spaced, primarily deep iron surrounded by a halo of rust. Knowing that the majority of targets were iron, the detector’s low volume target response to threw me a curve. In one of the field discrimination modes passing the coil over a iron target the TID jumped from around 5 to the mid to upper teens. Switching to the horseshoe “all metal’ mode verified the targets were iron. Upon review of the manual default settings for the search modes the “tone volume” settings are “4,25” for both field #1 and field #2 search modes.

This is what I am assuming: the low tone and lower positive TID response is caused by the non-ferrous components within the larger ferrous target(s); the low volume response is due to the default tone level of “4” of the Tone Volume setting “4,25”. The why?

This is what is confusing me: with a single frequency detector a low tone may indicate a deeper target, the TID may change as the hole grows deeper.  Attempting to understand what the detector was telling me, I switched through all the Equinox 900 frequencies 4, 5, 10, 15, 20, 40. The audio and TID response were all close to the multi-frequency response. I found myself switching by to  “all metal” and “dig it all” mode.

What am I am not seeing, hearing and doing?

Here’s a photo for your entertainment:

McCord March 1897 (outer fire door(s) steam powered equipment?)

 

 

[Chase Goldman]

57 minutes ago, HardPack said:

Knowing that the majority of targets were iron, the detector’s low volume target response to threw me a curve. In one of the field discrimination modes passing the coil over a iron target the TID jumped from around 5 to the mid to upper teens. Switching to the horseshoe “all metal’ mode verified the targets were iron. Upon review of the manual default settings for the search modes the “tone volume” settings are “4,25” for both field #1 and field #2 search modes.

This is what I am assuming: the low tone and lower positive TID response is caused by the non-ferrous components within the larger ferrous target(s); the low volume response is due to the default tone level of “4” of the Tone Volume setting “4,25”. The what?

What you are missing is that when you switched to 5 tones, the 2-tone/All Tone default volume settings of 4,25 no longer apply.  Look at the 5-tone default volume settings on the next set of default tables to get an idea of the default volume settings for each of the 5-tone regions (i.e., 12, 25, 25, 25, 25).  You will not hear the first tone (iron) region (i.e., TID 4 and below) unless you accept all regions using the horseshoe button.  Without horseshoe, you are likely hearing the big iron edge falsing in the 5 to 25 TID tone region at full 25 volume and a pitch of "6" vs. the ferrous region which is either silent or with horseshoe at volume 12 and pitch 1.  

If you want to take the ferrous falsing edge off, so to speak, then reduce sensitivity no higher than necessary (the 900 is hot/sparky and you get better TID stability and less ferrous "reactivity" with minimal depth loss penalty by adjusting sensitivity to around 17-20, the start adjusting iron bias upwards from 0, as necessary, to get mostly pure iron tones out of those test targets.  The tradeoff with higher iron bias is that some small non-ferrous may (and I emphasize "may" as I have never witnessed a non-ferrous target IDing as ferrous with higher Iron Bias settings) get an iron tone component.  I personally think this iron bias "penalty" is worth it unless you are going for micro gold or brass targets.  Increasing recovery speed can also lessen reactivity to iron targets.  HTH.

[HardPack]

Chase,

Okay, in either of the Field search mode 5-Tone Volume ranges from 4, 25,25,25,25 but the tone pitch ranges is 1, 6, 12, 18, 25.  For 'blanking" over discriminated targets I set the Threshold Level to "11" but left the Threshold Pitch at the default "4".  I started out with the Sensitivity at "28" but back down to "18" which calm the sparky audio down but did not eliminate it. The ground "auto-tracking" seemed to help but I just have to remember not to track out a desired  target. Originally, I jacked the target volume to 25 but settled on 22. ( I wasn't not using headphones).

I recall in a past discussion regarding transmitting power into mineralized ground and the effect on the return signal. I'll start by gradually moving up the iron bias setting; then set the recovery as required by a specific site. I think my individual problem may be with the ferrous "tone pitch" setting of 1 as related to the Ferrous Tone Volume setting of 4. I'll adjust the pitch range to see see what fits my hearing.

Mining sites are loaded with iron of all shapes and sizes, there needs to be a method to calm the Equinox 900 "sparky-ness without getting into a VLF vs PI "dig it all" discussion.

Perhaps Steve could change the title of this post to:

"ML Equinox 900 Big Iron Edge Falsing"

Thanks for the input, here's another photo of big iron:

Oliver 19.C ( plow shares?)

 

 

 

[Knomad]

Slightly off target but big iron related --

Believe it or not the most consistently accurate detector I have found for large Iron I.D in mining ground is Whites TDI SL, Yes a P.I machine.! The ground balance sets the crossover point for ferrous / non ferrous, and when set up right it is near flawless.!  

[HardPack]

Check out the ML Equinox 900 manual; page 39:

Topic  Iron Bias

under the headings

How Iron Bias Works

" All ferrous targets produce a combination of ferrous and non-ferrous responses. Large ferrous targets can present an even stronger non-ferrous response. Adjacent ferrous and non-ferrous targets can produce a similar response."

Lower Iron Bias Settings

" A lower Iron Bias setting (0-4 on Equinox 900, or 0-2 on Equinox 700) is recommended in areas where you do not want to miss any non-ferrous targets amongst iron trash, however more ferrous targets will be detected and misidentified as desirable non-ferrous targets.

When using a lower Iron Bias setting, detecting in All Metal Mode is recommended to avoid missing any desirable targets."

General Question:

With any detector including the ML Equinox 900, if you are detecting in an "All Metal" search mode, why would there be a need for feature such as "Iron Bias" for any setting at lower 0-4 or higher 5 -9?

 

Knomad,

No argument here the White TDI SL is still a go to detector.

 

[Chase Goldman]

13 hours ago, HardPack said:

General Question:

With any detector including the ML Equinox 900, if you are detecting in an "All Metal" search mode, why would there be a need for feature such as "Iron Bias" for any setting at lower 0-4 or higher 5 -9?

 

Not exactly understanding your question.  Iron bias works the same way regardless of whether you are in "All Metal" mode (- though this is more accurately described as "No Discrimination" mode as true "All Metal" mode means that there is no filtering or processing applied and you are getting the raw unprocessed target signal).  So operating in All Metal does not change the purpose for having Iron Bias, as Iron Bias changes the way both ferrous and non-ferrous targets are ID'd by the detector whether or not you are in All Metal.  Being in All Metal just allows you to hear the targets that ring up as iron.  All that Minelab is saying is to be cautious about applying too much IB as you may cause small non-ferrous to sound off as ferrous (which you will hear only in "All Metal") or too little in which case you will get more big ferrous edge falsing and nail head falsing that you will hear regardless of whether or not you are in all metal.  

19 hours ago, HardPack said:

Okay, in either of the Field search mode 5-Tone Volume ranges from 4, 25,25,25,25 but the tone pitch ranges is 1, 6, 12, 18, 25. 

Yep, I looked at the wrong column.

[HardPack]

Chase,

Since I have failed to find a Minelab definition for “Iron Bias” I am assuming Iron Bias filters the detector’s incoming return signal based on the purity of the signal. At Iron Bias setting 0 all signals pass through the filter regardless of purity or iron contamination; at setting 9 only the purest cleanest signals pass through the filter.

After running the Equinox 900 over multiple buried large iron targets I began to realize the detector is firing SMF signals weighted on the low or high side based on the search mode. So naturally the return fire of non-ferrous “falsing” signals is going to be proportional. 
 

As an example imagine an individual firing a single shotgun round into a flat rock, the ricochet return non-ferrous “falsing” signals are going to be proportional to the hardness of the rock face. Now imagine all your rock shooting buddies fire simultaneously multiple shotgun rounds into the same flat rock. The returning ricochet non-ferrous “falsing” signals is going to be overwhelmingly proportional.

Now as the light starts to shine in I am beginning to realize with either single frequency or multiple frequency the return signals are anything but consistent or “repeatable”.  On old mining sites I often search out the iron and will switch to “all metals” mode (with no Iron filtering) listening for low tones and negative TID to confirm the target is iron. With the Equinox 900 SMF I may be able skip the All Metals step.

Thanks for the response, I’ll get there,

 

 

 

[Chase Goldman]

2 hours ago, HardPack said:

Since I have failed to find a Minelab definition for “Iron Bias” I am assuming Iron Bias filters the detector’s incoming return signal based on the purity of the signal. At Iron Bias setting 0 all signals pass through the filter regardless of purity or iron contamination; at setting 9 only the purest cleanest signals pass through the filter.

Iron Bias is not a pass/no pass ferrous filter, that's what disc is for.  In an overly simplistic view (because all I have are my observations, as ML has failed to explain it in a meaningful way to the end user),  Iron Bias takes a target that has both ferrous and non-ferrous attributes and emphasizes the ferrous attributes (TID and audio) depending on how much Iron Bias you apply.  Iron Bias requires multifrequency to do its "magic" (so it is not present when in single frequency) and like all these signal processing tricks, it's imperfect and can be fooled into making non-ferrous sound/ID as ferrous if set too high or will not quiet falsing on big iron if set too low.

The following thread has some thorough and thoughtful discussion on iron bias.  It's Equinox 600/800 based but the fundamentals apply to the 700/900 as well.  It's not clear whether ML incorporated the Fe or F2 iron bias filter into the 700/900 or a third variant.  I suspect they further refined the F2 filter.  Note also that 0 doesn't necessarily mean that no iron bias filtering is being applied (vs. single frequency which definitely does not have an iron bias filter).

 

[HardPack]

Chase,

Great discussion on Fe vs Fe2, it appears to me that Minelab may have, for whatever reason, dropped the Fe2 feature on the Equinox 900. For now I am going follow Steve’s lead, set the Iron Bias to “0”  then field adjust the Sensitivity, Iron Bias & Recovery Speed. I am beginning to like the Field 2 search mode. As soon as these storms pass through I’ll head out. 

Thanks for the link