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Auto Sensitivity, how good is my dirt?

D

Dailydigger

New member
I have noticed that the auto sensitivity will change depending on my dirt sometimes it will be at 14 and sometimes it will hit 22. I just hunt parks here in Arizona and the ground is pretty hot around here. The CTX is more stable than the Explorer Se.
 
Its a lot better than mine. In A+3 I get 8-12 and I'm really happy when I see 18 (lots of top soil).
HH
 
Using Sensitivity to judge your dirt is one of the best features of the CTX. When Auto gets down too low, you need to start forcing the limits of stability in Manual.
 
In Auto+3, my CTX runs from almost max sens to as low as 7(rare). Mostly hi teens but much better in rich loamy stuff.
In Manual, I can always force a bit higher.

Remember every site is different and you need to match the settings to the soil.
 
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.
 
Certainly it affects it Chris, but soil can change drasticallyin content and that is also a factor. There isn't always spurious electrical.
Not to mention what man has done to the soil. Ever hunt near an old iron furnace?
 
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.
 
In the Houston area I run it in manual at about 26-27 ALL the time. The only time I ever see the 'auto' numbers or pay any attention to them is when I am on some sort of Iron ore driveway. Many years ago some folks made their driveways or roads out of a red crushed looking dirt, and that is tough to hunt in.
 
Champ,

We debated this until the cows came home in the old days. The original explorers did not show what the sensitivity level was in auto. Many or most of felt the the machine would dial the sensitivity way lower than needed in high trash ground. Basically it sees all the trash signals, thinks it is EMI and cuts sensitivity. The CTX shows you what it thinks it should be running at. I can detect up at our lake place, around the cabin there is EMI and trash. A few feet away ground that has never been developed. Same dirt, much different recommended levels.

Chris
 
MrWilburino,

I've turned my Explorer XS detector on in the house around electronics and wires and generally could not run sensitivity higher than single digits or it would go nuts. This is with the coil up in the air. Don't remember if I've done it with my CTX. I do know I've used it many times outside, under power lines, near electric dog fences, much lower sensitivity. Get away from the EMI, then I'm able to crank the sensitivity up. Same dirt. If we are considering high trash, especially ferrous content to be "dirt" different story. As I posted below an abundance of targets can cause the machine to dial down the sensitivity.

Chris
 
Chris, I'm not saying that the CTX isn't affected by EMI; it definitely IS, just like any other machine, which is why we sometimes have to turn the sensitivity down to deal with it. What I am saying, based on observation, is that when the CTX is being run in auto sensitivity, it does not automatically adjust the sensitivity level to compensate for EMI like it does for ground mineralization. Nor does it show any changes in the recommended sensitivity number (the green number) based on EMI levels. Changes in auto sensitivity and the recommended sensitivity number appear to be based entirely on feedback from the ground tracking system. The only time the CTX appears to monitor (and adjust through channel selection) for EMI is during the noise cancel process.
 
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
 
mrwilburino said:
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.
Click to expand...


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
 
Chris(SoCenWI) said:
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.
Click to expand...

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

Chris, I don't think your assumption is correct.....matt
 
metalpopper said:
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
Click to expand...

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
 
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