This is my personal belief, I think that the algorythym used to help discrimination among other things like ferrous content, includes in the program an algorhythm programmed to disregard items that are 1. Smaller than a small button, 2. Any object that generates an eddy current that is not interpreted to be generated from a round object.
NOW, if this theory is correct, using just those two criteria would help you eliminate 80% of trash targets. If it's smaller than a small button and not round, chances are good it is trash.
Perhaps that is why we have such a hard time with pull tabs ! They are round, larger than a button, and non-ferrous.
Think about a coin and relic machine. Most items you are looking for, buttons, coins, mini balls, rings, have some things in common. They are round, they are larger than a small button, and they are non ferrous.
If you take a one gram nugget and rub it right on the coil of an Explorer or a Sovereign or a Quattro, the machine does not see the item at all. It is smaller than a button, and gold nuggets are rarely perfectly round.
Once you get a nugget larger than a small button you can detect it.
We all know how well these machines discriminate. Well let me pose a question, if we know how to make a coin machine that discriminates so well, why can't we make a gold machine that discriminates just as well ?
The SD2200D, GP Extreme, GP3000, can find gold down to sub grain pieces, but they cannot discriminate a boot tack, or a small piece of wire. They discriminate out large ferrous iron pieces fine, but I believe this is because they are using a simple ferrous non ferrous discrimination that works on large pieces.
SO, can you find gold with the Explorer, Quattro ? Yes, if it is large enough. However, the majority of nuggets are 1 gram average and these machines would be hard pressed to be able to target these small gold nuggets.
BCOT!
DOC
