need some education on VDI readings

[mapper123]

I hunt with a White's XLT & need some help on the VDI readings. I thought the higher the reading (90-92) was indicating brass, copper or some other non ferrous material, but as often as not it is a aluminum can.
I need some help understanding my VDI readings!

 

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[steve1357]

Basically the VDI reading on detectors are best guesses based upon the conductivity of the target AND the size of the target. The size of the target is assumed to be a coin in it's computations, therefore when you get an aluminum can which should have a low VDI, it comes up a high VDI reading because it is much larger than a coin.

I sometimes raise my coil after pinpointing it's depth. It usually says it's a quarter at an inch or two, but you'll be able to still pick it up a foot above it. Obviously not a quarter......

 

[mapper123]

Thank you steve1357....you nailed what I was looking for.