High Sensitivity & Fe Bounce - Short Video

[earthmansurfer]

I've seen people mention the correlation in the title before and Moonshine mentioned it the other day. So, I played with it, moving between manual 30 sensitivity and a neutral auto (25 or so) on a lot of targets. Here is the first target I played with. It was just a pull tab at 5" or 6" but that is not the point - I get the same reaction on coins.

A higher sensitivity does indeed cause the Fe numbers to be more bouncy (in particular on an open quick mask screen) for a variety of reasons. There are two I can think of and that make sense in my ground:

1. - I have iron mineralized ground and running the sensitivity higher just picks up more of the iron mineralization, thereby "distorting" the Fe number. I guess it's averaging or picking up the target along with the ground.
2. - There is a fair amount of deeper iron in my ground. You can run the E-Trac totally quiet with no iron nulls in auto neutral, most of the time. But move it to manual 30 and the nulling starts. Again, there must be some kind of averaging happening.
And maybe 3. - Perhaps running the machine hot just makes the machine less stable (as is with most machines). Fe numbers are more bouncy but the CO numbers are not any where as impacted.

Also, there is a difference when you run some discrimination at high sensitivity compared to an open quick mask screen with the same high sensitivity. It appears that running some discrimination decreases the Fe bounce, but I am not sure here. Chime in with your experiences and ideas. I think with discrimination the E-Trac filters out some of the iron (via trash density high? I should test this. and gives a more stable Fe number. Just a thought.)

Now, I think it is dangerous to simply say "Drop the sensitivity to get the Fe numbers more solid." Well, yes, that is true but you will lose depth. If you don't get nulling from deep iron it's because you aren't picking it up, so if there are any coins at that depth you might not pick them up either (depending on size, conductivity, masking, etc.) I have tested this on coins in the 7" - 9" range in my soil and it is quite clear that once the sensitivity drops in the 20 to 24 range (in my soil) depth is greatly impacted. Remember, there is some kind of boost process at sensitivity 25. You can observe this quite clearly by switching between 24 and 25.

So, my suggestion is to know your soil and ground iron content. From there you have to decide if there are coins at fringe depths. How important is a quiet hunt to you? Play with the sensitivity settings. Unless you have high ground mineralization (or the like), you won't get the "brights in the fog" problem, but you have to test that out.

As I've said before, I don't have but just over 100 hours on the E-Trac, so I am still learning it big time. So, jump in here with your ideas, suggestions and corrections

Enjoy,
Albert

ps - Click on "youtube" in the lower right of the video and watch it there at 480 (have to choose that at the bottom).

[video]http://www.youtube.com/watch?v=yiz5g85KpaI[/video]

 

[mike4663]

Albert I will add a little here, hunting in ttf the other day in higher manual sensitivity with the 6x8 coil on from what I thought the detector was running fine, but when I would try to pin point with my sun ray probe I would just get a constant grunt with the probe in the hole and the only way to stop it was to lower the sensitivity. So my ? is was I running the coil hotter than I should of, or is the probe that much more sensitive than the coil, after switching back to auto I found the only good find of the hunt, 1880 indian on edge at 6". Mike

 

[Ken in Georgia]

sweet video!!!!

 

[niterider_58]

Nice video

 

[earthmansurfer]

Mike - I have never tried a SunRay coil so don't really know what to say. If you have bad ground and are pumping all that sensitivity through it, I imagine that could be the reason? Usually larger "coils" have more problems in bad ground as they just pick up more of the bad ground. I have never heard this about the SunRays, perhaps try over in that forum (I think there is one here). Nice find and congrats - would love to find an Indian. When I come back to the States, whenever that is, I will be like a kid in a candy store. No matter what I find it will be like starting over for me. After all, I have found 2 penny's and one dime (a silver Mercury!) here in N

 

[mike4663]

Mike - I have never tried a SunRay coil so don't really know what to say. If you have bad ground and are pumping all that sensitivity through it, I imagine that could be the reason? Usually larger "coils" have more problems in bad ground as they just pick up more of the bad ground. I have never heard this about the SunRays, perhaps try over in that forum (I think there is one here). Nice find and congrats - would love to find an Indian. When I come back to the States, whenever that is, I will be like a kid in a candy store. No matter what I find it will be like starting over for me. After all, I have found 2 penny's and one dime (a silver Mercury!) here in N

 

[earthmansurfer]

Mike - I understood what you were saying. I sort of see the Sunray pinpointer as essentially a very small coil, albeit elongated, that is why you can plug it inline to your detector and can transmit the signal to the machine and the machine can give accurate VID numbers with the signal. But I didn't mean to confuse you (or me!) with words. I think it would still perform as a small coil as far as having less surface area facing the ground and not overloading. But perhaps that is only true to a certain amount. Like I can max out my 6X8 SEF coil with no problem but can't my larget 15X17 as it picks up too much ground. So, what I mean is that perhaps when you have a 1" wide "coil" (probe) with all that energy going through it, it sort of overloads (for lack of a better word). All theory on my part though.

 

[E-TREC-Virginia]

The SunRay probe is just a 1 inch coil which works just like any other coil. You can scan a hole with it and get the same FE/CO numbers as the larger coil, or you can push the pinpoint button and pinpoint with it. Two things that would cause a small coil (probe) to false and/or grunt and that is a target overload or the sensitivity set to high.