Garrett Ace 350 Owner's Manual page 26

Once you have determined how your test targets register
on the Target ID during bench tests, test them in the soil. Bury
your targets at recorded depths to create a "test plot." Note
how various targets read based upon whether they are lying
in the ground flat or at various angles.
Keep accurate records or surface markers to indicate your
test plot targets and their depths. Try testing these targets
again in several months after the ground has settled, during
periods of extreme drought or after a soaking rain. Take note
of any changes in how these targets are detected.
The following illustrations depict a ACE 350 in ZERO Mode
scanning selected targets during a bench test. (Note: these are "air
tests" conducted in a pristine environment. The target ID scale can
be influenced by the soil as well as the conductivity, permeability,
thickness, size, shape and orientation of the target.)
TARGET
Small,
rusty iron
nail
Aluminum
foil
TARGET ID DISPLAY
ACE 350™
25