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DeepTech

Why do you lose depth when increasing discrimination?

Ground usually produces a signal of about 1Hz to 2 Hz, depending on how 'bad' your ground is.
Look at it this way. If you are set to just reject a surface nail, you have already rejected the ground signal and then some, and a high-conductive coin is far from that rejection point. Thus, only a little bias towards the ground and small iron, but virtually nothing close to high-coin rejection.
Shift that point of rejection along the scale and you have put the very low conductors, ground and small iron and such, way at the other end of the spectrum and now instead of having only mellow rejection of iron you have pronounced iron rejection. The reverse of this is that you have minimal acceptance of conductive targets.
Perhaps not in a proper 'scientific' explanation, but I am trying to get the message across. That's why models such as the Eldorado & Tej
 
A lot depends on the design of the detector. Most of today's high end detectors don't lose depth when raising the level of discrimination because they don't try to reject the target until after all the signal processing is done and then the CPU selectively decides what sounds reach the speaker and which ones don't. The detectors that lose depth when you raise discrimination are using designs where the unwanted targets are being rejected by the reciever circuitry and work pretty much the way Monte explained. Both types of machines are still currently available. The Minelab Explorer is one of today's designs that doesn't suffer from depth loss when raising the discrimination. A detector from the 1980's that didn't lose depth when raising it's Discrimination Level was the Teknetics Mark I.
HH
Beachcomber
HH
Beachcomber
HH
 
Monte, what you are saying then is that there is less depth loss if the 180 is kept at the lowest possible setting? I always prefered the 120 which I normally kept at 0.In your opinion which is more efficent 120 or 180? Thanks, Jerry
 
Would it be correct then to assume that the higher priced metal detectors use the design of discriminating after the signal has been processed? Does it cost more to manufacture a detector using this system of discrimination? Please have a great day! Kelley (Texas) <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=":)">
 
No not really. It all depends on the manufacturer's design. I am sure money comes into the picture somewhere along the line as well as the features. But I think it's what ciruitry the manufacturer has patent rights to as well. There are a lot of variables besides money that come into play. The more sophisticated a machine is the less the likely it will be lose depth due to increased levels of discrimination is probably a good rule of thumb but obviously it won't be true all the time.
HH
Beachcomber
 
Detectors that are specified to have "audio discrimination" are the ones that don't lose depth with disc control adjustments. Not all are terribly high priced.
Would be interesting to throw in an extra bit of circuit for "depth discrimination". An adjustment to reject very strong shallow coins and junk for those who only hunt the deeper older stuff.
HH
 
I got the same impression you did from Monte's explanation, Jerry -- that you will get more depth at minimal disc settings with ED-180 Tesoros. The question is how *much* more depth? I'm not sure you'd get enough of an increase to notice, but I've been wrong about stuff before <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt=";)">
How more efficient 180 is over and ED-120 Tesoro pretty much depends on the trade-offs everyone has to make with any detector made. You get better ground handling with 180 as Monte mentioned, but at the same minimal settings, 120 is more efficient at knocking out small iron bits than 180 because that's pretty much what 120 was designed to do, meaning you won't spend nearly the same amount of time bothering with little iron. But on the other hand, small targets don't temporarily "disappear" in a big honkin' plug of dirt while checking the plug in disc mode with 180 like they're more apt to do with 120.
IMO, higher or lower efficiencies pretty much depend on what you're using a particular detector for and your particular personal preferences.
Scott
 
Last Sunday I turned my Disc down to foil and dug 11 nickels(most ever in one day).
This is with an Eldorado uMax useing the 7" concentric coil.
So Monday night I did some air tests( I agree that air tests are not conclusive) and found the 7" coil would gain almost 2 "(on nickel) if disc was dropped from foil to just above iron.
It certainly has convinced me that I will be experimenting with less disc next weekend.
Not conclusive or the experience of an expert or old timer in the hobby. But it has promising possibilities <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=":)">
 
or easier detection of conductive targets.
A model with an ED-120 discriminate circuitry doesn't really have a 'O' adjustment, just a "minimum" setting. At minimum, the ED-120 will be a little above iron nail rejection. A <EM>true</EM> ED-180 circuit will accept all metals at the minimum discriminate setting.
 
theoretically true that increased disc doesn't result in less depth with many digital models, such as the Explorer, but pose the question on the Explorer forum and you will get many XS users saying you have to use minimal disc to get the deepies.
in real hunting conditions (junk, mineralized ground, interference) you find that a deep coin will not hit in high coin necessarily but a seasoned user may get other clues.
 
Monte, I am wondering if any specific Tesoro model is best suited, then, for hunting deep coins (silver) in fairly trashy parks with quite mineralized dirt. I am in Wisconsin and the dirt over most of the state seems to be "bad" in that the mineral content limits disc. mode coin depth to about 6". Never got a coin over 7"!
I am looking at buying a Cortes for the features, but if another model is better suited to getting depth in this bad dirt, I may be changing the plan.
 
While I generally don't like digging old nickels because they're almost always so trashed from so much moisture being held for so long in our clayey dirt, I've found this to be true as well except I don't have to do all the way down to foil for them to hit really well. I set my disc betwen nickel and foil (on or just a hair under "4") to knock out the ancient balled-up wads of foil that scouts, picnickers, and others have left strewn all over our woods here but still hit nice and hard on the old Buffaloes and V's, which like most coins in my woods, are hardly ever very deep anyway. But if you're stuff's deep and you don't have much sandwich-wrap foil to worry about, then definitely run it at or just below foil disc for the extra touch of depth doing so could provide.
Scott
 
When I bought my Treasure Mate from Les he asked me if I could check it in the bad mined dirt I had around here and I sent him this report. I found out something about target separation along the way.
I had the Treasure Mate in the toughest ground around here today and it works just fine.This is the situation in the ground I talk about. Possibly target separation is the big problem here. The ground is the mine refuse from anthracite coal mines. There are lots of low grade coal in the dirt. The dirt itself is black also. A metal detector will sound off on the coal like it
 
I understand what your saying about the nickels being trashed. I use them as a test material because they are close to Gold in conductivity. And I too can get the nickels between foil & the nickel logo.
However I have found that depending on depth, soil condition and moisture content of ground they can and have ranged from just above iron to the nickel logo here in Iowa. Seems like a broad range but I have dug them over that range.
If it were just the nickel I would probably not care too much. But knowing Gold is in the same range and not yet having dug Gold Rings or Jewelry. I am willing to push the limits of my trash tolerance to get some Gold. I have gotten some cheap plated rings and Sterling but the Gold has evaded me.
 
I cant take it any more. Im sitting here with tears running down my face after your description of that bad dirt. I will probably have nightmares tonight. I hope none of that stuff gets washed down hill to Texas. <img src="/metal/html/frown.gif" border=0 width=15 height=15 alt=":(">
 
Luck for around here that dirt is located in places where some fill dirt is used or some road beds and a lot of rallroad beds and its gets mixed in a lot of places where it is not so such pure bad dirt.
Just was wondering why my detectors don't get the depth in a lot of places and its seems between that dirt and bog iron there is a differences in a lot of places. I usually check with a test target what kind of depth to expect. We got little mountains around here . Hills a hundred feet high or more in some places that have grass and some trees on them and the terain is not natural its big hills of mine dump stuff covered over with thin top soil and grass.
When I was a kid and a lot of mines were still working around here except for the black color the ground around here looked like some of those old mining areas you see out west. Only I think much bigger with the long big un-natural hills that look natural to someone who hasn't seen them before the cover up.
HH
Dan R.
 
Thanks Scott,
And to show how disc and sensitivity effect each other, ( Eldorado air test),turning the disc down to iron or below will cause you to reduce sens if you are in or near the max boost zone.Turning disc to preset will allow higher sensitivity.It seems like a tradeoff.I wish I could hold the higher sens with the lower disc.
Jerry
 
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