Minelab Tech Article Says Too High Of Sensitivity Can Cause "False Discrimination". Hmmmm....

[Critterhunter]

I've never heard running sensitivity too high quite put that way, and this is by a Minelab technician so it carries some weight in terms of pondering that. Of course we all know too high of sensitivity can cause falsing, which in effect might cause you to miss a deep target by not hearing it, or at least mistaking it as just another "false" to ignore.

But, I found with my 15x12 that it seemed to get best depth, or at least ID at depth, with the sensitivity much lower than what was max stable. Usually it wanted it set around 3PM or perhaps right at the letter "C" in noise cancel on the GT's face plate.

Anyway, there's been some speculation in the past from some Sovereign owners, myself included, that too high of sensitivity in certain soils (even though still stable) might actually cause a deep coin to null out like iron instead of sounding off. I always attributed this potential to the machine being overwhelmed by the ground signal and the coin signal just pushes it over the edge into nulling out...Mainly because the coil is running so hot that the coin is being washed out in the ground signal, and so when it hits the coin it's a real "dirty" signal that just looks for the most part like a spike in the ground signal and is nulling out on it. I never really ran any tests to prove this one way or another, but I have read from a few others about my suspicions...That they found too high sensitivity, at least in certain levels of ground mineralization, would cause the coin signal to null right out. I honestly believe this is more of a factor when using a bigger coil, like say any coil bigger than the stock 10" one, but I have to say the 12x10 doesn't appear (yet) to suffer from this, or at least from a degraded target ID by running sensitivity too high like the 15x12 would do in my soil. I've read similar "nulling" or at least target degradation reports from WOT users in some forms of mineralized soil. Bigger coils= Bigger potential for this problem I think.

But, back to the point...That "false discrimination" thing in that tech article really has me thinking. Perhaps with too high of sensitivity in certain soils, even if the machine is still stable, it may be discriminating out a coin at extreme depth as just iron, or even just sounding it off as some other form of junk lower than a coin on the scale. Tests are in order, for sure.

Now, don't just think this is a Minelab thing. That article was relating details about VLF detectors in general in this respect. If anything, it went on to say how multifrequency is able to better determine the ferous/non-ferous nature of the signal over typical VLF detectors.

We all know about the "high beams in the fog" thing where too high sensitivity can cause you depth due to mineral reflection. That's probably the wrong way to put it. A better way would be to say that ground "glare" can over power the target signal if the sensitivity is too high. Not to mention that too high and a bit unstable sensitivity can mask targets due to noise. But, this is something VERY different they are talking about here...A new angle to that old "high beams in the fog" thing...They are saying too high of sensitivity can cause "false discrimination". That doesn't sound like "ground glare" to me, but rather the ground signal causing the target's ID to change to something that it's not, which means it's either then discriminated out or at the very least ID'ed as something other than it's true nature.

Ponder that for a while. It's something very different then the old ground glare thing. Caused by the same issue? Yes, Minelab says it's caused by the ground signal disrupting the target's ID. It's less of a problem (they said) on a Minelab due to the way it handles the ground signal (a unique way that is NOT conventional ground tracking....Something MUCH better than that), but never the less it is still a problem.

Again, I've never heard running too high of sensitivity being put this way...."false discrimination". It's a new way to look at the issue of sensitivity other than just the fog in the head lights then or causing too much falsing. It's an interesting possibility to think about, because I found the 15x12 would degrade the target ID at depth with too high (but still stable) sensitivity set. I think I remember Gunnar saying his WOT would null over a coin with too high of sensitivity in his soil. I can't honestly remember if my 15x12 would null over a deep test coin if I raised sensitivity too high. It might have a few times, but at least I am sure that it often wanted sentivity about 1/4th to even 2/3rds LOWER than max stable to achieve best/easiest ID at depth.

 

[Critterhunter]

Here's the quote from the article...

"The sensitivity to discriminating targets (how deeply a target may be detected) is controlled by a sensitivity control. Hence, in mineralised soils, the sensitivity control must be made less sensitive in order to avoid false discrimination."

Most of us know that running sensitivity super high can make iron give false coin hits more than running it lower. Perhaps that's related to this? But I think it might be implying more than that...That a high sensitivity in certain soils with various forms of mineralization can cause a coin to ID say down the scale as something else?

 

[Rick(ND)]

Too much sensitivity can give false signals and those that know their Sovereigns can tell the difference I have seen. Too much sensitivity can see the target that is disc out more than seeing the actual good Target too so you will get a null instead of the actual good signal. This is where going slow comes in handy as going slower you can hear the good signal with the disc out target. Get a deep actual target you barely get, then sweep a little faster and it is gone, lower the sensitivity and sweep slow and then fast and see what you get. Now raise the sensitivity a bit and maybe not max as it will chatter too much and try it real slow and notice how you hear it and then sweep faster and see you will not hear it at all. This works for those deeper signals and those not too deep you may not see much difference.
The Sovereigns are a amazing detector for those that spend the time to learn it, those that don't spend the time or swing too fast will not be as happy with this detector as I have seen it many times over. I wonder how many of those Minelab Tech really use and understand their Sovereigns and go more by what they have read and not what they have experienced, then there are those that spend the time and really know how to get the most from their Sovereigns and I bet it is from experience and not what they read. The point is I would take the advice of those that we know that have learned their Sovereign from actual in Field use and not those that read how it is suppose to work. There is book smart and there is common sense smart that learn from Experience which I feel is the best way, don't you??


Rick

PS: I too read those that are book smart and do try some of their ideas on actual hunting to see if they will work or not.

 

[gear box]

Very good advice Rick. I'm no expert by any means, but with my limited experience, that is exactly what I have found. I haven't found any super deep coins yet but only moderatly deep, say 6 and a half to 7 and a half inches. But with the testing I did at these depths with the high and low sensitivity and the fast and slow sweeps, Slow sweeps and mid sensitivity wins every time. My finds recently have bearing this out. Thanks Rick for all your advice.
Good luck Gary

 

[deepdiger60]

I will agree Slow sweeps and mid sensitivity wins every time the last 2 days i was running to hot at back bay beaches normally i run between 10 and 11 am at the big ocean beaches with no problem my thought now is the smaller bay beaches has a lot more salt content which caused the GT to false in 2 feet of water when i walked up to the wet sand area it stopped but when i did hear a good target it showed good numbers on the meter then it nulled then i could not find that target again all this happened 2 days ago yesterday someone on here told me to lower my sensitivity to around 1pm and guess what that worked fine i got a few targets in water and wet sand one Target was a deep quarter 3 scoops to dig it out , live and learn bay hunting is much different then ocean hunting at least here it is , ill admit beach hunting is new to me for the 3 years i use the GT on farm fields and old farm sites some 370 years old where it ex cells !!! beach and inland i guess are 2 different worlds but since i recently retired i have plenty of time to practise . This forum is great thanks people for all the valuable information . Jim

I thought i would show my oldest find ever with the GT 2 silver flan coins paper thin only 6 inches deep sitting on a large stone in a heavy wooded area on a old farm out here in Oyster Pond the 2 coins most likely came over with the early Dutch sailors early 1600,s King Ferdinand and King Leopold 1626 and 1632 Netherlands the only older thing i seen found out here is Barry,s 1617 silver spanish cob .

 

[Ron from Michigan]

Jim,nice finds.Thanks Ron

 

[Critterhunter]

Rick, while experience is a good teacher, there are also other ways to learn...And I personally will ponder and weigh any words of wisdom dolled out by a Minelab technician very carefuly for consideration myself. After all, if you can't rely on them for any "inside" information or unique perspective on these machines, then who else would you look to for any technical clearity in those respects? My points is that I've never heard using too much sensitivity put quite this way before. We all know about the fog in the headlights thing caused by ground glare, and we all know about too high of sensitivity causing instability and noise, and thus could cost you noticing deep targets. But, in all my years, I've never read of anybody ever saying that too high of sensitivity can cause "false discrimination". That sounds like something very different to me, and being that it comes from a Minelab technician I think it deserves careful consideration and even some experimentation in the field. I'm more than willing to explore this myself, as it might even explain the reason why too high of sensitivity with the 15x12 would cause bad or less easy target IDs on my GT like the coin was junk, where some setting much lower than max stable gave the best/easiest ID at depth. I always assumed this was due to ground glare, and in a sense I'm sure it's still the same contributing factor, I just never thought of it as "false discrimination" and that opens up other interesting possibilites.

We all know that a super deep coin gets to a point where the microscopic iron in the soil will overwhelm it and cause it to read as iron. That's at the very outter fringes of detection depth before it slips out of contact with the detection field. But, once again, to me that's a very different thing than what I would call "false discrimination". It makes for at least a new way to look at and consider the possibilities to me of what might be going on with maxed out sensitivity.

Again, this is not a Minelab only thing. They were talking about VLF in general in that respect. If anything, they go further into detail about how BBS and FBS do a better job of making the ground signal less of an issue in distorting the target ID and ability to see the target at depth, but it still appears to be a problem for Minelabs, but less of a problem.

 

[gear box]

Nice old coins deepdiger60. Hard to believe they made coins that thin.
Good luck Gary