Posted by Reg on 5/10/2008, 8:21 am, in reply to "Re: The problem with iron"
75.71.144.124
Hi Rick,
There is no comparison between a PI and a VLF in how things actually work. Now, with that said, sometimes the only way to explain things so they make sense is to refer to something on a VLF but when I do, please keep in mind that the reason I do that is to try to let people know what one might expect. I realize the last statement is confusing but that is the only way I can figure out how to state something.
Now, the GB circuit on a PI takes a later sample and subtracts that sample from the main signal. When this is done at the right ratio, the ground signal is minimized. So, bobbing the coil will generally result in little or no signal, much like what you would hear on a VLF.
At ground balance, some objects will cause a high tone and others will cause a low tone. Which tone they generate is the result of the objects conductivity. Low conductive targets such as foil, small gold, small lead, and some of the ferrous objects will cause a high tone.
At GB, other objects that are higher conductors will cause a low tone. These are objects that such as large gold, most silver, copper, and other higher conductors. Larger lead objects may cause this also. It all depends upon the GB setting and the size and conductive characteristics of the object.
Ok, now, if we can eliminate one of the tones, then we can basically discriminate out all objects that create that tone. This is what the single tone feature does. So, when I select the low tone only, I do not hear any signals coming from tin foil, small gold, small lead, etc. This is how I operate the GS 5 in a park.
Here is the important feature of this GB/disc thing. As I adjust the GB control, objects very close to the ground signal in terms of the balance setting will change from a high tone to a low tone or visa versa. One nice thing about this feature is in my area, the GB setting is very close to the point where I can change the tones of most ferrous objects. So, by adjusting the GB a little either way, I can cause ferrous objects to be ignored or sound off depending upon which way I adjust the GB control.
On the down side, as I adjust the GB control to cause ferrous objects to be ignored, I also lose some depth capability of detection on most higher conductive coins. In other words, if I do not want to dig much iron at all, then I will not be able to detect the deeper silver and copper coins. So, I have to be careful of the actual GB setting.
Now, getting back to your question about gold rings, at the GB setting where I can detect silver and copper coins, I will also detect some tabs, and most aluminum screw caps. I will also detect thicker gold bands, but ignore thin ones. This characteristic is somewhat similar to that which happens on a VLF. On a VLF, if you eliminate nickels, you eliminate most small gold rings or fine gold chains. On a PI, the same is true. So, when detecting silver and copper coins, I will not detect small thin gold rings or thin gold chains.
Also, keep in mind the size of ring I will detect is dependent upon the GB setting. So, if I turn the GB up, I will detect silver and copper coins deeper, but I will also detect more ferrous objects. I will also detect smaller gold, but still not small enough to detect very small gold thin rings.
On a VLF, if you set the disc such that you detect pull tabs, you will detect some gold rings, but ignore others. This will happen on the PI also.
So, detecting "micro jewelry" with a PI can be done, but you will detect most tin foil also. Again, this is much like what happens on a VLF.
This single tone mode works much better for coin hunting, when hunting parks. It doesn't work that well for detecting small gold. The actual size of gold wedding band that would be detected will vary with the GB setting, so there is no way to say for sure just what size ring will be detected and what size will be ignored. As a general rule, the very thin bands will be ignored, while thicker ones will or could be detected. This may mean a mans wedding band may be detected while a similar style womans band may be ignored. Again, it all depends upon the GB setting.
Keep in mind that the ground can change across the country. Normally, this means the actual GB setting at perfect GB will vary some, but generally not a whole lot from place to place. This means at perfect GB, the actual ferrous objects that are ignored can vary. This would explain why George K may not find many nails at normal GB, where he is hunting now, but may find some or more at a different location.
Also, keep in mind that right at GB, there will be objects that will be ignored just like the ground signal is ignored. So, if the ground varies enough, then it is possible that some ferrous objects will be ignored even when using the dual tone feature. These particular ferrous objects have a signal identical to the ground signal so they are ignored. If this is what is happening, then any coin or other desirable object buried near that particular ferrous object will be detected much easier, which basically says one can "see" through some ferrous objects, much better.
So, one should be able to detect some objects below some ferrous objects. Unfortunately, a different ferrous object may have a different null point on the GB setting, so that object will cause a different level of interference in the detection of a coin below or near it.
I hope this makes sense.
Reg
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