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Old 07-06-2017, 01:20 PM
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BottleCapKing BottleCapKing is offline
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Originally Posted by longbow62 View post
I hear people mention a good way to tell if a target is worthy of digging is changing swing direction to see if it I.D. numbers stay the same or similar. I get that I think, but what if there is say a nail near it or another trash target that might change the numbers if swing direction is changed. I have not been doing this long enough to know if what situations the change of swing direction could fool you into not digging a good target.
You can get widely varying VDIs on a target if it is not symmetrical in all directions. Take a rectangular pull tab as an example. If you swing across the narrow side, you get one VDI. If you swing across the long side, you get another number. If you swing across it diagonally, you will get yet another number.

Coins, rings (for the most part), washers, pull tab rings, etc are either symmetrical in all directions or close to it (depending upon the design of the ring, or the type of pull tab ring). They will give you fairly consistent VDIs in multiple directions. One exception is pieces of can slaw. They tend to have consistent VDIs as well, regardless of shape.

Originally Posted by longbow62 View post
What about a coin not lying perfectly flat. Could changing swing direction on a coin close to or on edge not drastically change the I.D. numbers? No one wants to pass good targets, and no one would rather dig every trash target. On most of the sites I hunt digging everything is just not feasible.
There isn't much of a change in VDI with coins at varying angles. I have done a good deal of testing on many coins at 0, 30, 45, 60, and 90 degrees. The angle at which the coins sits mostly affects your ability to actually detect the coin and your ability to accurately pin point it. This is why it is very important to pin point from multiple directions.

Image a coin lying in the ground like this: / When you pin point this coin from the edge side ( <--> / <--> ), it will pin point to the left of the coin. If you pin point it from the coin face side, it will pin point closer to the coin.

It is very difficult to deeper coins that are on edge. When deep coins on edge are found it is because there is usually iron in the hole as well.


Originally Posted by longbow62 View post
On anther note I dig a lot of targets that read exactly like solid coin numbers. I just know I have a coin and it turns out to be a washer or small semi coin shaped piece of metal. Copper tubing does this a lot too. Am I missing something? Does everyone get fooled by this stuff?
Metal detectors cannot tell the difference between and a disk of metal that produces similar response field characteristics. The detector is really looking at the depth of the target, the phase shift of the response field, and the strength of the field compared to approximate depth of the target. It compared these things with with what it expects from desirable targets. Sometimes you get conflicting results that swap between VDIs. I experience this with Large cents on my MXT/MXS, it is copper so it thinks it is probably a penny and indicated that by VDI, but size wise it thinks it is a quarter and reflects that as well by VDI number. So, when I find a LC, it I am seeing VDIs switching between 75 and 84. It can't really make up its mind on a positive ID. There is no detector that can tell you with 100% certainty what is under the ground. That last best discriminator is between your ears.

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