NASA Tom or others...question about Minelab Explorers and semi-auto vs. manual sensitivity...

Talked to a guy on another forum, using an Explorer II, who related this story...

Has a dime buried at 7". He wanted to see how sensitivity would affect depth of detection of this target. He had his machine set at semi-auto sensitivity 16 -- which both he, and I, understood to mean that the machine was thus selecting the "best" sensitivity level, less than or equal to 16, that the software felt the machine could run "optimally" or "sufficiently stable" at. He saw the dime, at semi-auto 16, so he slowly lowered sensitivity until he lost the dime -- which occurred at semi-auto sensitivity 8. So, he assumed that the machine was, at that point, choosing a sensitivity level less than or equal to 8. Thus, he "knew" that switching over to manual sensitivity (forcing it to run AT 8 sensitivity), that he would of course still see the dime. HE DIDN'T. NO DIME. So, he started upping the manual sensitivity until he re-acquired the dime. He had to run it up to FIFTEEN before he could see the dime again. He switched back into semi-auto, dime still seen, and he then started lowering sensitivity again. Again, the dime disappeared at 8 semi-auto; then back to manual, NO DIME. He again had to run it up to 15 manual before re-acquring the dime.

Either his machine is screwed up, my understanding is screwed up, or Minelab has not effectively explained how semi-auto sensitivity works. It appears, in this example, that this guy's machine in semi-auto is choosing a stable sensitivity setting, but one that appears to be ABOVE the numerical value he had selected. This could be an incorrect assumption, but that's how it appears based on his testing. I was aware that the machine could choose a sensitivity well BELOW what number you had it set at, when running semi-auto; I never saw ANYWHERE a suggestion that it could choose a sensitivity ABOVE, let alone SIGNFICANTLY ABOVE, that level.

What is going on here? I thought I understood setting the sensitivity on these machines, but this throws me off. Is there something ELSE advantageous about running semi-auto sensitivity, behind the scenes in the software, that is "helping" the machine run better (and thus see that 7" dime) at only 8 sens., as opposed to running a higher manual sensitivity? Is there more going on here? Or is it simply that, despite instruction materials from Minelab, that when running semi-auto sensitivity (at LEAST in the Ex. II) the machine has the ability to run a HIGHER sensitivity than what you have set? This is a very important point to understand, in my opinion, in terms of understanding how your machine operates, and how you should be setting it up in different scenarios. Until now, it has been MY experience that when trying to hit a deep target, that using a high sensitivity AND setting it MANUALLY, can allow more depth (as opposed to running semi-auto), but at the potential cost of less machine stability/more falsing. But this, of course, is at HIGH sensitivity levels, where the machine (if set in semi-auto) would naturally be choosing something lower. Is there something ELSE that goes on with semi-auto sensitivity, when you are running very LOW sensitivity levels?


Thanks,

Steve

What you write here is exactly my experience aswell.

16 is 16 is 16 when in auto, even if you have your auto sens at 12 or 25 it is still 16. If it was ever ment to be otherwise it does not work.

I have tested this both with lower and higher sens levels and auto sens is always at 16 or very close to 16 as in manual sens.

Meaning, if you want to adjust your sens away from 16 either up or down, forget auto. You have to use manual.

I dont know if this is corrected with the E-Trac but it is like this on the Explorers. The E-Trac has however the blind spot on bigger silvers when in Normal soil mode so I rather have the Explorer.

[www.youtube.com]

Very interesting, frnifo. Both on your experience that "16 is 16 is 16" in semi-auto, and that the Etrac has a "blind spot" on bigger silvers in some settings...

Steve

"Semi-Auto" sensitivity option has always been WELL below optimal performance. Not a bad program for beginners.........but......... otherwise, quite a hinderance. Too conservative.

It has always been my understanding that whilst in Semi-Auto Sens......... internally, this electronic platform is unalterable.........regardless of user input. Only 'manual' Sens has user alterable effect.

Eye-opening youtube.

Best advice I can give use what works best for you in your neck of the woods and don't get fancy with Explorer settings as different settings, mineralization, external interference are all dealth into the equasion.

Over the years certainly a debateable and many do well with either as far as depth and stability..

Always remember my first day with an Explorer XS hunting an old grove pounded to death by many units over the years. I used quickstart and recovered 11 targets from 6-12 inches ..8 wheaties, buffallo nickle, old merc. and a walking half..Needless to say my pinpointing was atrocious but was an old field and was of no consequence. DD coil was sure different from a concentric but with time in the field learned to pinpoint well.

Never was able to recreate that first day ( perhaps it was the mineralization, humidity or maybe was just lucky.)
With the help of an experienced Explorer user set up a general program using manual sens. that worked well in my area but never forgot that first day in quickstart and moved onto a 11 and SE model but the weight proved to be a downfall and went back to a CZ rather than injure my arm or back.

No technical ability on my part and drive a car but sure couldn't overhaul the motor kind of situation and would advise an ardent Explorer user to experiment and set up a workable program for their neck of the woods as imagine this debate will continue to go on and users will excell either way.

semi-auto is an odd bear. I know when you air test the two that auto has a definite cut off where as manual it continues to attempt to id the target. Is it possible it adjusts more than just the sensitivity... like the gain and channel which manual doesnt? Could this lower setting increase the processing ability over manual which might not be correctly set? There could be a point where this changes on the up side that since most use higher sensitivity that we just havent noticed? If it changes more than just the sensitivity then can we really tie depth to a specific sensitivity? Because i know if you have your sensitivity to high you tend to pick up disc targets and EMI that may reduce depth and you might have been just as well off using a lower setting. Dan's right thou these explorers have to be adjusted to your location. Thats one reason i like mine because their settings are flexible and somewhat forgiving.

I run it allways manual 26-30. On semi hammered coins are gone.

DewCon may have a point in regards to 'gain' being affected. Somewhat like the disc settings on the T2 effects the gain (or something like it) which is 'automatically' built into the unit disc function.

I played around a bit today and you are correct at the lower settings semi seems to have the edge.... but as you move up the scale it reveres its self and manual is the king as you loose TID and stability.

Dew

noise cancel at 10
gain 8
thres tone...1
var.....10
limits ..10
pitch hold
deep on
ironmast 26

as most know i hunt the beach 99% of the time.......waste deep to top of damp zone...almost daily.............minute and half video.

during many of my spins i have found targets that GT's and Excals. can not hear unless i remove a few scoops of sand..........all with auto32

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[www.youtube.com]

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Edited 1 time(s). Last edit at 05/05/2011 11:40AM by gravediggermax.

hey gravedigger --

Thanks for the video. Looking at your settings, that's the same way I run my SE Pro -- except that I usually don't run "deep on," and usually run a disc pattern instead of iron mask. Nonetheless...I find it very interesting that you could not hear the target in MANUAL 32, but could in semi-auto 32. Obviously, that suggests that the machine was choosing a different (lower) sens. setting, but one that "worked better." That in theory is how I understood that semi-auto was SUPPOSED to work; however, I have the OPPOSITE experience in my test garden. To hit a deeper coin, I have to run my manual sens. up to the 28-32 range. Once acquired, if I switch over to semi-auto -- at the same numerical sensitivity level -- the target disappears.

Fascinating.

Steve

i have iron mast set at 26, but like u run a very tight discrimination pattern..........and hunt in it.

i have tested several deep targets while hunting with other excals..........none could even hear until i would remove several shovels of sand from the top, then they could be up the target and in all of those cases, it was a deep dime.........i was fooled yesterday and thought for sure that low siginal was a dime.

i will do more testing daily.....except for today.......r a i n.

good luck

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Yes, it is an eye opening youtube but maybe we can try to figure out whats really happening here.

The E-Trac has the added "benefit" of a soil selection, difficult and normal . I like to think that the difficult setting is what the explorers are preset to and that the normal setting is the new option in the E-Trac trying to move the gb point closer to -90s .

I believe the gb point on the explorers and E-trac difficult is permanently in the salt region and therefore it is very hot on silver cause its far from silver region. And not so good on small gold and dont find coke at all cause its close to the balance point.

Remember, Minelab dont say the machines groundbalance, they only say they compensate. The gb point is fixed and by the new option in the e-trac you have two different preset points.

Back to the youtube where the big silver goes silent, it is a classic wraparound error cause the machine dont handle the gb point being in the normal -90s like we have on other detectors.

The silvercoin in the vid wraps into the - part of the gb wheel and disappers.

Thats my view on the subject anyway.

Others ?