Findmall.com
 
 






Minelab CTX 3030 Detecting Forum


Welcome! Log In Register
That is why I never use auto, EMI will kill sensitivity, my brain can tell me how high to run sens.
Posted by: jtalley007
Date: May 21, 2017 08:31PM
Professionals and Minelab engineers say use auto and add plus numbers and maybe in a vacuum or laboratory that would work.

But in my humble opinion adjusting manually for the level to suit you was always best. I proved it time and again in the field on deep targets.

I ran my old explorer XS as maximum sensitivity as I could and in clean ground in middle of the woods may have been wide open.

I'd get a deep bullet reading in manual that was a squeak only. With sensitivity on 32 I would select auto and the reading would go away every time.

That was even more pronounced with the sovereigns. They stunk in auto.

Same has been true with the CTX. People can say what they want about auto and sure it as a good use but Sure not around EMI IMHO!

Jerry

avatar
Re: Auto Sensitivity, how good is my dirt?
Posted by: amberjack
Date: May 24, 2017 05:24AM
only found one spot where manual is more workable than auto and that's my experience in my conditions..

AJ

Re: Auto Sensitivity, how good is my dirt?......This reply is the correct one
Posted by: metalpopper
Date: June 06, 2017 08:02PM
Quote
mrwilburino
I'm not so sure about emi affecting the sensitivity level. I've tested this out a couple of times by carrying the machine (with coil in the air) from an area of fairly low emi to an area of high emi (and vice-versa), with no change at all in the recommended sensitivity number or the actual sensitivity level (was using auto) until the coil was back on the ground and swinging. I think it's strictly tied in with
the ground tracking system and based on mineralization levels.


mrwilburino's post is spot on.

Auto-sens LEVEL is indicative of GROUND conditions.

Normal 'inert' ground produces a reading of 16 usually; goes LOWER for increasing FE; HIGHER for moist, acidic water contents in a soil.

Any extreme changes from 16, is best counteracted by going manual and adjusting sensitivity appropriately....only you on the day/site can judge that.....matt

Re: It's not the dirt, it's EMI that regulates sensitivity...Don't agree...matt
Posted by: metalpopper
Date: November 22, 2017 01:36PM
Quote
Chris(SoCenWI)
It is electrical noise that determines sensitivity level. Out in the country or in big parks sensitivity tends to run pretty high. In town, especially near power lines sensitivity runs low. Same dirt.

***********************************

Chris, I don't think your assumption is correct.....matt

avatar
Re: Auto Sensitivity, how good is my dirt?......This reply is the correct one
Posted by: sgoss66
Date: November 23, 2017 09:03AM
Quote
metalpopper
Normal 'inert' ground produces a reading of 16 usually; goes LOWER for increasing FE; HIGHER for moist, acidic water contents in a soil.

Any extreme changes from 16, is best counteracted by going manual and adjusting sensitivity appropriately....only you on the day/site can judge that.....matt

I don't agree with this, that "normal" "inert" dirt would mean a CTX-suggested sensitivity level of 16. I don't believe this is correct at all.

I also don't agree that what makes your machine capable of running higher sensitivity is soil that is more moist and acidic.

I have reddish-colored clay where I live -- i.e. irony dirt, and the dirt in most areas is on the "slightly basic" or "slightly alkaline" side, in terms of pH reading, at about 7.8 or so. CERTAINLY not acidic, and often the soil is dry (I live in Oklahoma). So, based on what you are implying, my dirt should result in the CTX suggesting a sensitivity level lower that 16 -- it's irony, it's often dry, and it's far from being acidic. However, in this dirt my CTX runs well above 16...

I think most would agree with the assertion that "less mineralized" dirt allows you to run sensitivity higher, and "more mineralized" dirt requires you to run it lower (if you want quiet, stable operation). And yes, high iron content in the dirt is a type of "mineralization," that would likely require lower sensitivity. But I don't believe that a "16" on the sensitivity scale suggests "inert" dirt. I believe this to be completely incorrect. On the contrary, "16" is actually suggestive of dirt that is moderately mineralized, as I understand it.

My understanding/belief is, the more "inert" (i.e. less mineralized) the dirt is, the greater the sensitivity level you could run at (and still maintain quiet, stable operation). I believe that extremely "inert," non-mineralized dirt would allow you to run maximum sensitivity -- i.e. something close to 30, NOT "16" as was suggested in the post I quoted. From this perspective, it's the iron in my dirt (at least in part) that results in my suggested sensitivity level always being lower than 30 (usually running around 20 or so). As I understand it, a number lower than 30 suggests mineralization; the lower the number the more mineralized you are. I don't think "16" has anything to do with anything. Low mineralization, higher sensitivity. High mineralization, lower sensitivity. That's what I've always understood, and am almost positive is correct. In other words, something closer to "maxed out" at "30" would be suitable for very inert dirt, not "16." A suggested sensitivity of "16" on the CTX is actually suggestive of fairly mineralized dirt, NOT "inert" dirt.

Steve



Minelab CTX 3030
Minelab Equinox 800
Garrett ProPointer AT
Lesche hand digger
Lesche 38D Ground Shark "King of Spades"

Norman, OK



Edited 5 time(s). Last edit at 11/23/2017 09:31AM by sgoss66.

Re: Auto Sensitivity, how good is my dirt?......This reply is the correct one
Posted by: UncleTom
Date: November 23, 2017 10:30AM
I'm with you Steve, that is my take too.

Re: Auto Sensitivity, how good is my dirt?......This reply is the correct one
Posted by: metalpopper
Date: November 29, 2017 08:30AM
Quote
sgoss66
Quote
metalpopper
Normal 'inert' ground produces a reading of 16 usually; goes LOWER for increasing FE; HIGHER for moist, acidic water contents in a soil.

Any extreme changes from 16, is best counteracted by going manual and adjusting sensitivity appropriately....only you on the day/site can judge that.....matt

I don't agree with this, that "normal" "inert" dirt would mean a CTX-suggested sensitivity level of 16. I don't believe this is correct at all.

I also don't agree that what makes your machine capable of running higher sensitivity is soil that is more moist and acidic.

I have reddish-colored clay where I live -- i.e. irony dirt, and the dirt in most areas is on the "slightly basic" or "slightly alkaline" side, in terms of pH reading, at about 7.8 or so. CERTAINLY not acidic, and often the soil is dry (I live in Oklahoma). So, based on what you are implying, my dirt should result in the CTX suggesting a sensitivity level lower that 16 -- it's irony, it's often dry, and it's far from being acidic. However, in this dirt my CTX runs well above 16...

I think most would agree with the assertion that "less mineralized" dirt allows you to run sensitivity higher, and "more mineralized" dirt requires you to run it lower (if you want quiet, stable operation). And yes, high iron content in the dirt is a type of "mineralization," that would likely require lower sensitivity. But I don't believe that a "16" on the sensitivity scale suggests "inert" dirt. I believe this to be completely incorrect. On the contrary, "16" is actually suggestive of dirt that is moderately mineralized, as I understand it.

My understanding/belief is, the more "inert" (i.e. less mineralized) the dirt is, the greater the sensitivity level you could run at (and still maintain quiet, stable operation). I believe that extremely "inert," non-mineralized dirt would allow you to run maximum sensitivity -- i.e. something close to 30, NOT "16" as was suggested in the post I quoted. From this perspective, it's the iron in my dirt (at least in part) that results in my suggested sensitivity level always being lower than 30 (usually running around 20 or so). As I understand it, a number lower than 30 suggests mineralization; the lower the number the more mineralized you are. I don't think "16" has anything to do with anything. Low mineralization, higher sensitivity. High mineralization, lower sensitivity. That's what I've always understood, and am almost positive is correct. In other words, something closer to "maxed out" at "30" would be suitable for very inert dirt, not "16." A suggested sensitivity of "16" on the CTX is actually suggestive of fairly mineralized dirt, NOT "inert" dirt.

Steve

_______________________________________________________________________________


Steve. :-
I don't agree with this, that "normal" "inert" dirt would mean a CTX-suggested sensitivity level of 16.
I don't believe this is correct at all
.

******************


Matt :- Steve, my use of the word ‘inert’, was intended to be convey a soil/ground whose CHEMICAL activity was low, as well as inferring low in ferrite mineralization.

16 AUTO-sens. is the E-trac’s default level, as dictated by the Minelab experts.

Two questions for you Steve. (1) Why do you think they chose that figure as the starting/default level?
(2). Can you demonstrate/indicate your understanding of what the Auto-sens’s numerics relate to, in terms of the soil’s make-up/components, that produce the range of variations from 0 to 30?
You are very assertive regarding what’s not correct, but very vague about the alternatives.
Perhaps you can oblige me, in my pursuit of learning, for I don’t have a local natural source, of ‘hot’ soil.
I do have several test-beds of contrived activities; FE down to 4 in auto-sens terms, and as high as 20.
……………………………….
Thanks for your engaging posts; for it was your mention of pH reading that caught my attention, and I assumed from that, you were a detectorist who thought ‘a little deeper’ than the average ‘beeper’….matt.


avatar
Re: Auto Sensitivity, how good is my dirt?
Posted by: sgoss66
Date: November 29, 2017 01:39PM
Matt --

I DO try to "think deeper" about detecting; I'm a scientist by profession, so thinking a lot about things is the way I'm wired. But, since the field I work in is not related to electronics, I can't speak to many of the technicalities regarding detector design, electromagnetic waves and waveform analysis, etc. etc.

Having said that, I will answer your questions based on what my understanding/thoughts are...

1 -- Why did Minelab set the default sensitivity at 16? My understanding of it is that Minelab chose a relatively LOW sensitivity setting as the default, a level that would be "low enough" that the machine would run "quiet" or "stable" in a majority of soil types, but "high enough" to still give decent depth. My understanding is that the default "16" setting was one that was low enough so as to ensure a relatively quiet, stable machine in a majority of soil types found in most areas, but still find coins to respectable depth.

To turn the question back to you -- IF my understanding is wrong, and yours is correct -- that "16" is the appropriate sensitivity for moist, acidic soil with low iron content, then why would my machine, running in dry Oklahoma red clay display a recommended sensitivity level well above "16" at almost all times? One could assume that since the "red" color is due to iron oxides present in the soil, then if your understanding is correct my machine would want to run below the "16" level, right? If 16 is the "right setting" for "low ferrous-contaminated soil," as you noted, then my red clay should push suggested sensitivity LOWER than 16, right?

2 -- What is my understanding of auto-sensitivity numbers, relative to soil mineralization? Well, this gets pretty technical, with a need to understand things like reactive and resistive (X and R) signal components, and current induction, and time decay of current, etc. etc. etc. You probably know most of this already, but some here will be bored stiff and couldn't care less. So, I apologize in advance to all those who don't care about these technicalities, and you can skip all of what I'm about to say. Also, as a disclaimer, I don't have FULL understanding of all this, as -- again -- my scientific knowledge lies outside of electronics. But, to answer your question, here's an attempt at a simplified (hopefully) version, that hopefully isn't too flawed by the areas where I lack full understanding...

Sensitivity control runs from 0-30 on the CTX, 0 being "minimum," and 30 being "maximum;" on this I think we agree. Now, while a detector is trying to detect a buried metal object based on inducing electrical current in that object, and then analyzing the characteristics of that induced current, the issue of course is that electrical current is ALSO being induced within the ferrous component of the soil. And since the soil signal (emanating from the induced current in the soil) is much stronger than the target signal (emanating from the induced current in the target), there needs to be a way to both "subtract out" the soil signal so that you are left only with the "target signal," AND a way to "amplify" that remaining -- but weak -- target signal so that the machine can process the signal.

The way a user controls how much the detector "amplifies" received signals is through the sensitivity setting. IF the soil is "mild," and/or IF the detector is doing a good job of dealing with the soil's ferrous content (i.e. accurately subtracting it from the target signal), then increasing sensitivity should allow the machine to "see" a "good" target deeper into the soil. HOWEVER, IF the soil is highly mineralized, OR if the machine is struggling to "subtract out" the soil's ferrous effects, then the machine's ability to accurately ID non-ferrous targets within the highly ferrous ground breaks down. In other words, some soil signal is mis-characterized by the machine as "target signal." And in this type of situation, increasing sensitivity will therefore amplify NOT ONLY that weak target signal, but ALSO will amplify weak ground signals which have "bled through" -- i.e. BOTH signals get amplified, and you end up with noisy, unstable machine operation. "Falses" will increase...ground noise, in other words...as the machine struggles to figure out what is "target signal" and what is "ground signal."

So, bottom line, the less "mineralized" the soil is, the better the machine can separate soil signal from target signal. And thus, when "amplifying" the strength of the return signal to be processed by the unit by raising your sensitivity setting, you can increase the unit's ability to "see" a target deeper into the dirt. But, conversely, the more "mineralized" the soil is, the less effectively the machine can seprate ground signal, and thus both get reported to the user at times as blips and chirps and whispers of "non-ferrous" ID...such that amplifying these signals (through increasing your sensitivity setting) only leads to a noisier, less "stable" audible output to the user. Obviously, in this kind of situation, lowering the sensitivity from a high level down to a lower level will reduce the "chatter," by instructing the machine to "ignore" weak signals received by the machine. The GOOD is, you get a quieter, more "stable" audio presentation, but the BAD, of course, is that you are ignoring not only weak SOIL signals that have "bled through," but ALSO weak signals emanating from deep "good" targets. THUS, you lose "depth," and thus the tradeoff...high sensitivity means better depth, BUT more "chatter" in a mineralized dirt; low sensitivity means less "chatter"/more "stability," but also less ability to report deep targets to the user.

FINALLY, what Minelab tries to do with auto sensitivity, is adjust it up and down, depending upon the amount of "chatter" that the machine is receiving; in other words, if too much ground mineral is affecting the machine's ability to discriminate/identify, then it "dials down" sensitivity; if the machine is experiencing very little ground signal "bleeding through," then it "ramps up" sensitivity so as to give the user a better chance of seeing deep targets. Obviously, Minelab ALSO allows a more experienced user the ability to adjust this for themselves, thus the "manual" sensitivity setting. But for a less sophisticated user, who would likely "have more success" with a quieter, more "stable" machine, Minelab uses a conservative, auto-sensitivity setting as a default, to allow better chances for these less-sophisticated users to have "success" (albeit with some implicit loss of depth).

Now, I may not have SPECIFICALLY, EXPLICITLY answered the question regarding what EXACTLY the auto sensitivity numerical values relate to, in terms of soil make-up/components, but I hope that I answered it at least in a slightly indirect or somewhat implicit way.

Steve



Minelab CTX 3030
Minelab Equinox 800
Garrett ProPointer AT
Lesche hand digger
Lesche 38D Ground Shark "King of Spades"

Norman, OK



Edited 3 time(s). Last edit at 11/29/2017 01:52PM by sgoss66.

Sorry, only registered users may post in this forum.

Click here to login