Sensitivity and wet ground... an observation

[Nick A]

We've had a lot of rain here, keeping the ground moist. I've been using the E-Trac in auto sensitivity (would run about 18-23 range) and finding silver, wheats and indians. All good until yesterday. I hit some sites, even one I had pulled silver from just the previous day and another site that has been littered with wheaties. I got almost nothing old or deep in a whole day of hunting. Only one coin I considered deep was a 1911 wheat. Weird, I thought, but sometimes that happens, bummer.

Well, I gave it some thought overnight and today I got out for a short lunchtime hunt. I decided to forgo the auto sensitivity and turned it up to 27 manual (I run 29 on my Explorer). I started hitting deep wheats immediately. First hole was a 1917 and 1931 in the same hole. All were deeper than my plugs cut with the Lesche, I had to scoop these out of the bottoms of the holes. I dug a handful of all deep wheats... a good sign for silver for sure. Sadly, I had to come back to work, but I have some more holes to dig in a few hours.

Anyhow, here's my surmise... the wet weather increased or enhanced the detection depth, so the auto sensitivity was decent and effective. Once we had two days without rain and sunny days to dry things out, the auto sensitivity wasn't enough to get the kind of depth I expect at my previously hunted sites.

Normally I am not one to say "max out the sensitivity" and I am not saying that here. The E-Trac was rock solid in auto. Trash sounded scratchy like trash, coins hit hard. Which is great if you want coins only and no trash. However, this is a lesson to me, to get more of these iffy-deep hits I have to run in manual sensitivity as I do with the Explorer.

 

[rbholt80]

thats exactly the conclusion i came up with a few months back. I dropped the sense down low over a target that was deep and iffy and i lost it. so i ran it back up to 27 and the tones came back loud a clear but still iffy. I dug and found a 1912 wheat from about 11 inches.

 

[JohnnyI]

Nick, I just read your post, I immediately bundled up the detector in plastic (raining here too), turned the sens way up to 27, and in a few minutes got a small signal from my completely "no conductive readings left" worked out iron patch. The signal was a mere 01 ferrous and 05 co, sounding like the low hummm of foil (but reading too deep for foil) which I dug for the heck of it because ANY non ferrous signal is a rare joy in this experimental patch. At about eight inches was small piece of old brass about the size of a half or quarter worn farthing (but enough of a non ferrous find to show me that both the wet ground and higher sens, along with some attention to the really oddly low comnination of both ferrous and co numbers, may eventually result in another worn liard, pewter, gold, or something equally small and interesting. Thanks. Johnnyi in rainy N.J.

 

[Chris(SoCenWI)]

As far as I've read the auto/manual works the same in the E-trac as the older explorers. But it does show on the screen where it is really running at in auto sens. This is something we had speculated about for years; the feeling was that the sensitivity in auto could vary hugely from the setpoint, and now we know for sure. It was good that Minelab listened and made this data available on the E-Trac.

You say the wet weather enhanced the detection depth. I agree 100%; I don't even bother to detect in the summer when the ground is dry. But I don't think it has anything to do with auto/manual. If you had cranked it to 27 manual when the ground was wet you would have gone even deeper.

Basically how high you can turn up the sensitivity has to do with ambient electrical noise. In town around power lines I often can not get it above mid teens. I seldom find any deep old coins at these sensitivities except when the grass is very short and the ground very wet. Out in the country can crank up to upper twenties in places and get a usable machine. Definitely find more deepies then.

In auto sens the machine will back down the sensitivity in high noise environments to get a stable threshold. My guess is that the machine can not tell the difference between the noise generated when sweeping the coil over lots of targets and electrical noise, and will back down the sensitivity in trashy environments. And over the years there have been many posts about people seeing how an area came alive with targets once they switched to manual and cranked up the sensitivity.

Chris

 

[Nick A]

The rest of the evening... 24 wheats, four silver coins. Only one "modern" coin, a memorial cent and not much trash. In fact at the one site (where I was skunked on Sunday) I dug the three silver and nothing else. No trash, no clad, nothin but silver.