Loss of depth by using discrimination

[mts]

So I was doing some air tests with my Tesoro Silver µMax and noticed that the depth capability decreases as I raise the discrimination level.
There is about a one inch difference between no discrimination and full discrimination. I realize that air tests are not necessarily indicative of what you get out in the field but it got me to thinking. Basically, there could be situations in which the discrimination control would give you false information due to this phenomenon. Imagine a quarter sitting just at the threshold of the detection range. With the discrimination set at a normal hunting level (below nickels) I would pick up the signal. But as I rotate my discrimination control toward silver coins, the depth capability of the machine may decrease at a point to where the quarter could no longer be detected. Yet the discrimination control would not have gotten to the silver coin range. This would make me think that the coin was a penny or even a pulltab.

I tested my Vaquero and my BH Tracker IV and they don't suffer from this problem. Is this a common problem/behavior for beep and dig machines? I don't see this mentioned very often.

 

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[Sandman]

It is true that dialing in to much disc loses you some depth. A weak signal from a coin near the max depth of the detector will also drop out if the coin is on edge as it only reads the top surface and not the mass. This is what is known as learning your machine. Even detectors of the same model may operate different from each other due to variations in components.

 

[mts]

Thanks sandman. So this is fairly common for many machines? I can see this being more of an issue with "beep and dig" machines and those of us who "thumb dial" our "TID" so to speak. If it weren't for the fact that I was changing my discrimination on the fly to identify the type of target I don't think that it would be as big of a deal. Of course, knowing that I will get less depth by setting my discrimination higher is valuable information in and of itself.

So it is definitely something to think about. I don't see it mentioned very often so I thought I'd bring it up.

 

[ivan salis]

think of "disc" as "ignore" -- the higher your "ignore" level goes --the less overall "targets" you will find , but the better you machine will sort "junk vs treasure" (warning !!! too much disc can cost you good items --so be very careful on how much you use) -- it takes a bit of the machines "power" to run the sorting process * so theres a bit less power to devote to pushing the absolute max power into the soil (max depth)

thats why with "0" disc --all metal you get the best depth --all the machines availble power is focused into "pumping" signal into the ground and no signal of any type is ignored --but that is why you find a lot of trash as well

once one engages a "disc" program of any type it takes some power from the machine to "run" it --the more you disc --the more power is diverted to "running" the screening / disc program -- with a bit less power it will not reach as deep , but you will get better quality finds and less trash . --common sense there.

 

[U.K. Brian]

Interesting but totally incorrect theory. Power is not shared out. Zero discrimination doesn't automatically mean more depth, if its a detector with no ground balance control then the discrimination control provides a degree of ground balance and improves performance.

There's no way use or non use of discrimination can provide "better quality finds" and less trash is a questionable statement. You hear less trash but its effect is still there limiting the performance of the detector.

The minimum discrimination you can live with is the way to go and if your detecting a site thats got possibilities of older finds then the more rubbish in the ground the less discrimination that should be used.

 

[ivan salis]

ah uk brian -- if one spends less time digging "junky" trash item signals (by proper use of discrimation)-- thus spending more of ones time spent "in the feild" digging only good quality type signals * ( thus much more likely to be a good item) will not one's time be spent more "productively" - thus your ratio of good targets found per hour "in the feild" will go up =vs just digging every bloody thing? of course

the less trash -statement means --you will dig up less trash by using discrimation --no "trash item" signal = no digging up "trash items" --thus less overall trash "found" and less time "wasted" spent digging it up

of course the trash is still there and can in some cases "block out" nearby good items

I do agree of course --for optimal depth - proper ground balance * MUST be correct (* being properly ground "balanced" is the output of the proper maximum amount of signal sent out that the soil will actually fully accept )-- how much signal /power to use depends upon the sweetness / sourness mineralwize of the soil since for best preformance --you can only push as much signal as the soil condtions allow you to * --- a lot of folks try to "push" too much signal" in a vain attempt try to get "maximum" depth -- what they get is "excess signal feedback * which hurts rather than helps

as I say --sometimes --less signal power === better yeild results .

I have shown folks who own simple bounty hunter tracker IV machines that "freak out" at local beaches how the machines "see" the minerals in the wet sand and how by lowering their "power out /sensitivity level" how they in effect --"ground balance" the machine for the beach by matching signal output to the acceptible level the wet sand will accept .--thus making their machines "usible" --no more falsing *beep beep beep

some folks are of the "dig everything" mind set school -- others are not * frankly I do not want to dig everything -- I'm too wore out and of ill health to do it , so yes I might by pass a item or two now and then by using discrimation but I'm ok with that.

 

[U.K. Brian]

Sorry can't agree again and ground balance should almost never be "correctly" set. In most cases a positive or negative offset is better.

As for wet beaches very few single frequency detectors have the range of adjustment to effectively deal with wet salt so its better to use the discrimination control to balance out the salt effects. This will make most detectors run smooth as silk without the need to reduce sensitivity.

As for the general rather high levels of discrimination being used today if your not removing rubbish then it builds year on year and your local park or school field will end up effectively as a solid sheet of metal at some point in the future.

 

[ivan salis]

so your of the "dig it all" -- clean out where you hunt school -- thus basially anti discrimation / "0" discrimation --dig all signals school

 

[Silver Searcher]

so your of the "dig it all" -- clean out where you hunt school -- thus basially anti discrimation / "0" discrimation --dig all signals school

Yes would be my answer Ivan, why leave the trash in the ground, especially if you intend to go back there what you dig should be determined by your headphones, and the experience you have using your machine. Newbies would have to dig everything that's just the learning curve we all go through

SS

 

[mts]

An update on this topic.... I did some more testing with my Tesoro Silver µMax and found some very disturbing results. If I turned the discrimination all of the way up to max, the detection depth on a silver dime falls dramatically to below 1" (and gives a very broken signal at that). For a quarter it falls to 5" (down from 7" and 7.5" respectively).

I thought something must be wrong with the machine so I emailed Tesoro about it. Surely they didn't expect this to be normal behavior. I've only used this machine about 5 times so far. Well, their response is below:

Hi,
Yes, the more discrimination you use, the less depth you will get. At max discrimination, a dime will only get an inch of depth. At max discrimination, you will only find quarters, half and full dollar coins....which is the only time max disc would be used. you should be able to disc out most trash, while still finding coins without having to use max disc. Everything sounds normal...you will notice different coins will get different depths....try it using minimum disc, using coins and different trash targets.

The Silver µMax will air test various targets at about 5.5 to 7 inches (give or take) depending on the conductivity/type of target, and settings. The Vaquero is much deeper as you already know. The higher the mineral content in your dirt, the less depth will get.

If you think your detector is experiencing less depth than before, you can send it to us per the instructions on our website.

Regards,
Casey Stern
Tesoro.com


This is news to me. My Vaquero loses depth with higher discrimination but can still pick up a dime at 5". My BH Tracker IV can pick up a dime at 4" with max discrimination. I can't believe that this is expected behavior. I'm going to post something in the Tesoro forum to see if everyone else is getting the same results.

The bottom line is that I never would have expected that "max discrimination will only find quarters, half dollar, and dollar coins". If this is true then I don't think I can recommend the Silver µMax anymore. This behavior will completely change the way I use this machine. You can no longer thumb the discrimination knob expecting it to tell you what is in the ground.

I'll report back what I find. If anyone else has noticed the same thing (or something different) with their Silver µMax please feel free to chime in.

 

[Cappy Z.]

I might sound like a dreamer but I want a machine that will go two feet deep not two inches.

Cap Z.

 

[mts]

I might sound like a dreamer but I want a machine that will go two feet deep not two inches.

Cap Z.

Me too. This Silver µMax air tests at 7" on a dime which is actually about a 1/2" better than my Vaquero (of course, you can't trust air tests). That's why I'm surprised that at max discrimination it can hardly pick up a dime that is almost touching the coil.

 

[ivan salis]

max disc is for silver quarter and up ( silver half and dollar sized silver coins) hunters only .

its not 'rocket science" --- I think that its fairly clear that one should set ones disc level to the "proper" setting / level for the targets one is actually seeking ---and if one is seeking small silver like dimes and such*** one should set ones machine up that way discrimation level wize (so that they "ring up" at decent depth * ) -- the power you divert to the machines IDing process ( thus ignoring / blocking out unwanted items signals from ringing up and making it less sensitive to some metals overall)--the less depth you will get *

your deepest best depth --will be in all metal mode * (however you get "0" disc -)-- thats why simple "tone" type machines like the tracker IV were good -- because you use the sounds (3 differant tones) the metal you find "makes" in all metal mode to assist you in trying tio figger out if its good or not -- low tone = iron mid tone = aluminum & gold high tone = copper & silver

with the 3 way switch on the tracker IV -- you got 3 choices -- #1 (all metal MODE ) 3 "tones" high mid low --- #2 (tone MODE ) 2 tones only mid and high tone --no iron FINALLY #3 (discrimanation MODE) number of tones you will get depends upon how "high" you set your disc level . note by careful use of discrimation * and by adjusting it properly --many pull tabs can be disced out while still leaving in almost all gold items (only the very tinist type items might be lost -like a small post type earring or such. )

ps forget "the meter" on the tracker IV -- might as well put duct tape over it -- tracker IV is a "sound" machine --learn to listen very carefully to the tones the machine makes and set it up properly in disc mode and with practice , you should be able to figger out fairly well "roughly" what you found before digging it up in a lot of cases -- if after gold be forewarned -- IF YOUR GOING FOR GOLD * YOU WILL HAVE TO DIG TAB TYPE SIGNALS --BUT IF YOUR DISC IS ADJUSTED RIGHT NOT QUITE AS MANY .

 

[mts]

max disc is for silver quarter and up ( silver half and dollar sized silver coins) hunters only .

its not 'rocket science" --- I think that its fairly clear that one should set ones disc level to the "proper" setting / level for the targets one is actually seeking ---and if one is seeking small silver like dimes and such*** one should set ones machine up that way discrimination level wize (so that they "ring up" at decent depth * ) -- the power you divert to the machines IDing process ( thus ignoring / blocking out unwanted items signals from ringing up and making it less sensitive to some metals overall)--the less depth you will get *

I have a background in electrical engineering and have dabbled in building my own metal detectors. So I can tell you that your "power you divert to the machine's IDing process" is a load of bull. I let it go the first time so as not to stir up trouble but if you insist on continuously declaring it to be the case and then declaring "that it isn't rocket science" (as if you have some deep knowledge on the subject) then I'm going to call you on it. It has very little to do with power diversion and all to do with phase detection filters and such. It differs by machine based on how it is designed so it is impossible to declare that it is any one factor.

Your whole theory completely ignores the main issue. My Vaquero is designed such that I can detect a dime sized target at 5" with max discrimination vs. 7" in all metal mode. This is a 28% loss of depth which is in the "expected" range and is probably understandable. It is NOT true that hunting in max discrimination mode on a Vaquero is "only for quarter sized targets". As long as you understand the small decrease in depth capability it is perfectly fine to hunt for dime sized targets with max discrimination on this detector. On the other hand, my Silver µMax is potentially designed such that I can only detect a dime sized target at 1" with max discrimination vs. 7" in all metal mode. This is an 85% loss of depth which is NOT in the "expected" range in my opinion. Why should I expect this when I have two other detectors that don't behave this way? Why doesn't the Tesoro documentation point this out if it is expected? Why hasn't anyone else commented on it other than to throw out obligatory "it isn't rocket science, you should expect less depth when using discrimination" style remarks?

The whole point of this thread was to raise awareness of how much discrimination affects depth and why certain machines are affected more than others. Well, it certainly raised my awareness. I was not aware that a Silver µMax loses a whopping 85% of its depth on dimes when you turn the discrimination up to max. I'm wondering how many other Silver µMax owners were aware of that...

 

[ivan salis]

i agree -- a machine even at max setting should hit a silver dime which is at the "high" end detection wize on the matel scale --with iron at the low end and silver at the "high' end -- I was speaking about the Umax when I said -- "max detection is for quarter and up sided coins *" I meant in the U max model --as you say it does not ring up silver dimes at more than 1 inch at max disc setting -- so basically it useless for silver dimes hunting (1 inch at max setting is a joke)

ok i do have a question -- please explain how DOES a machine "power" its computer chip that "tells" one sort of metal from another thus running its IDing process without using ANY energy --from the machine ?

everything thats mechical takes some power to run off of --even if its a 1% tiny bit of "power" to run on --nothing is "free"

and 99 % of availble power is not as good as 100%

 

[mts]

i agree -- a machine even at max setting should hit a silver dime which is at the "high" end detection wize on the matel scale --with iron at the low end and silver at the "high' end -- I was speaking about the Umax when I said -- "max detection is for quarter and up sided coins *" I meant in the U max model --as you say it does not ring up silver dimes at more than 1 inch at max disc setting -- so basically it useless for silver dimes hunting (1 inch at max setting is a joke)

ok i do have a question -- please explain how DOES a machine "power" its computer chip that "tells" one sort of metal from another thus running its IDing process without using ANY energy --from the machine ?

everything thats mechical takes some power to run off of --even if its a 1% tiny bit of "power" to run on --nothing is "free"

and 99 % of availble power is not as good as 100%

I never said that power was free. In today's microelectronic circuits (many of which are microcontroller based) turning on a discrimination circuit should result in minute changes in power consumption which will hardly affect the transmit signal at all. Additionally, you forget that I am comparing a test with discrimination on and set at low to a test with discrimination on and set at max. Either way, the discrimination circuit is being used. It is just to what degree that it is being used. In other words, I'm not turning discrimination on and off. I'm adjusting a level on a circuit that is already on. A well designed detector will not see huge variances in output power based on such a simple change. Finally, it is possible to create a circuit that performs discrimination entirely in software. So "turning on" discrimination amounts to flipping a bit in memory and running a new algorithm. That is hardly going to change the total power consumption of the system. Your explanation is overly simplistic and is not based on reality. It may help you better understand the behavior but it isn't a good explanation of what is going on. It would be like saying that the brakes on a car slow it down because it takes power away from the engine.

You also stated earlier that you advise people to turn down the sensitivity on their Tracker IV's to turn down the amount of power being used in the transmit signal. This is also false. For most detectors, there is no way to "turn down" the transmit signal. The detector only transmits at full strength (why would anyone want to transmit at less than full strength?). The sensitivity control is usually a gain control on the receiver op amp circuits. It adjusts how much signal is "seen" by the discrimination/detection circuitry. Of course, it is possible to build a detector that has true variable output power. But most manufacturers of low to midrange machines don't waste their time with this as few people would ever use it.

You say that it isn't rocket science but it is clearly more complicated than you are trying to make it. I don't want to sound like I'm some sort of expert. I'm not. It is impossible to understand how each and every detector is made. So you end up speaking in generalities.

 

[ivan salis]

isn't controlling how much signal is seen by the cricuts "in effect' wize the same as varying the "output" of its signal ?-- it basically amounts to the same "bottom line" -- in rough "high mineral" type areas where the machine "overreacts" due to the high mineral content in the soil --making it less sensitive * allows for the detector not to "see" the minerals -- in effect acting as a sort of "ground balance" for a "otherwize" preset ground balance machine --while not the ideal situation if one only has a simple preset machine doing this could "readjust it in such was way that in could now be used in a otherwize "unusible zone"--abeit at a bit less depth.

 

[mts]

isn't controlling how much signal is seen by the cricuts "in effect' wize the same as varying the "output" of its signal ?-- it basically amounts to the same "bottom line" -- in rough "high mineral" type areas where the machine "overreacts" due to the high mineral content in the soil --making it less sensitive * allows for the detector not to "see" the minerals -- in effect acting as a sort of "ground balance" for a "otherwize" preset ground balance machine --while not the ideal situation if one only has a simple preset machine doing this could "readjust it in such was way that in could now be used in a otherwize "unusible zone"--abeit at a bit less depth.

No, controlling how much signal is seen by the circuits is not "in effect" the same as varying the output of the signal. You have transmit/output signals and you have receiving/input signals. They are different beasts. It is like comparing releasing the gas pedal vs. hitting the brake. The net result might be that the car eventually slows down. But they behave very differently and it is important for a new driver to understand the difference.

Changing the output signal effects how much EM field the target sees, battery life, and how much you may interfere with other detectorists around you. Changing the sensitivity does none of these things.

 

[Keppy]

so your of the "dig it all" -- clean out where you hunt school -- thus basially anti discrimation / "0" discrimation --dig all signals school

Yes would be my answer Ivan, why leave the trash in the ground, especially if you intend to go back there what you dig should be determined by your headphones, and the experience you have using your machine. Newbies would have to dig everything that's just the learning curve we all go through

SS

Myself i think if you want to find the good finds you should not use discrimation........

 

[George (MN)]

Concerning the Silver u/Max 1" dime air test at max, this setting would likely only be used by people detecting new parks trying to get the most $$ quickly.

I was wondering what the Silver u/max air tests at on a dime when disc is set just high enough to reject pulltabs? Or high enough to reject zincs?

I had a Tesoro Bandido II u/max & set it to reject pulltabs to detect a park. I was using the 10x12 concentric coil. 3" deep dimes gave a broken sound. When I turned the disc down to just reject iron & planted a nickel 6" deep, it got it with a solid & pretty loud beep. My ground has moderate iron & hot rocks.

Some of the better newer designs won't lose any depth when rejecting pulltabs, in an air test. The Silver u/max gets pretty good in ground depth for the price, as long as disc is low. If you want deep silver dimes while rejecting pulltabs, it looks like a different detector would be needed.

I recently obtained a Garrett AT Pro & it air tests 9.5" on dime, solid beep, high tone, with tabs notched out ($595 new MAP price). I had a Fisher F5 ($499 new MAP price) air tested 8.5" on dime w/pulltabs & below rejected. Best wishes & HH, George (MN)