It doesn't really matter what mode you use, "within reason" as most trash
items ring hot in the ring or coin range. So you are likely to pick them up in any
usable mode. Being that is the case, you have to learn to tell trash from coins,
or whatever desired items. And that is not always easy.
But some are. IE: cans.. Cans are pretty easy to discern as they are so large.
The usual trick to tell a can is to raise the coil up a few inches as see if it still
shows up. If it does, it's probably a can or other large item like foil, etc.
But a coin that is fairly deep will not show up when you raise the coil a few
inches because of it's small size.
The ID scale on the Ace 250 is audio notch. The machine is actually in all
metal mode all the time. It's always seeing everything. All the notches do is
turn the audio off for a certain notch range. This is actually good. The
advantage over this design vs older designs is no loss of depth when using
notching.
Caps and tabs can be difficult, but not impossible to tell from coins.
When caps start to rust, that can make them easier to tell apart.
The original cap might not be as conductive as a coin. But once it's
starts to rust, it actually becomes more conductive, as rust is more
conductive than the iron or steel the cap was made from.
This will cause ID "bouncing". It's often ringing low to med at times
hitting on the steel, but also bouncing up high, hitting on the rust.
If you get a bouncer, it's usually going to be trash of some kind.
Coins on the other hand hardly ever bounce around as far as ID.
They are usually stable and ring about the same every swing.
Also the sound of audio hit can be a clue. Some learn to tell tabs
by the sound they make, even if they are hitting in the usual nickel-
tab range.
But... I still usually dig them up, as some can be rings, or other stuff.
If it ends up a tab, it goes to the "trash" bag, never to be detected
again. :/ Just one less to run across in the future.
It's hard to avoid tabs if you don't want to miss nickles and rings.
So really, you are always going to dig some trash if you want to
make sure you don't miss anything good.
I dig most every target I come across unless it's obviously trash
due to bouncing ID, etc.. And even then, if you pass on it, you might
be passing on something peculiar like a Hot Wheels car, etc..
It's never a sure thing when dirt fishing.
Over time, practice digging all the various items over and over will
help you "sense" what the object is likely to be.
I don't know if any of this will really help, but there you have it..
