White’s Electronics MXT 300 - Manual (Page 17)

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Another example of when Lock would be used is if
a particular mineralized rock or patch creates dif-
fi culties in searching an area. A hard rock mine for
example with a low mineralized base rock and ran-
dom high mineralized rocks or patches. Place the
TRAC control in the Ground position and balance
"pump the search coil" over a representative sample
of the high mineral rock or patches. Then Lock in
that ground rejection setting "place the TRAC con-
trol in the Lock position". The entire area can then
be searched without the distraction of the inconsis-
tencies the high mineral patches create.
The Salt position provides an extended ground
balance and tracking range to compensate for
conductive salts also called alkali. Ground rejec-
tion against salt/alkali slightly overlaps the lower
end of the conductive target (metal) range. In other
words if you ground balanced against signifi cant
salts, some loss of sensitivity to lower conducting
metals (metals low on the VDI target scale) can be
expected. The advantage and performance improve-
ments of rejecting the salt, however, far outweighs
any loss. Because the Salt TRAC setting can track
well into the target range it is not recommended for
normal conditions, only for areas known to contain
salt. Salt water beaches for example or alkali desert
regions. The Ground setting will not track into the
nonferrous metal region. The Salt setting will. The
MXT 300 ground rejection system is capable, in
both the Ground and the Salt settings, of consider-
ing some iron a ground mineral.
If operating in a known salt area, salt water beaches
for example, it is not necessary to balance in the is not is not
Ground TRAC setting. Simply select the Salt
TRAC setting and proceed to pump the search coil
over the ground to be searched. The Salt setting
will balance and then track to changes identically
to the Ground setting only with an extended range,
well into the conductive target area.
Summary - The Ground TRAC setting is recom-
mended for most searching conditions. Lock is
used to hold a ground rejection setting that is fi rst
established in the Ground or Salt TRAC positions.
Lock is recommended for areas that cause detector
instability due to extreme ground peculiarities such
as a lot of decomposing man made iron. Salt pro-
vides extended ground rejection range to compen-
sate for conductive salt/alkali conditions. The Salt
setting can ground cancel extreme enough to reduce
sensitivity to low conducting metals, metals that ap-
pear low on the VDI scale. The Ground TRAC set-
ting will not balance nor track into the nonferrous
metal region. Despite this draw back the Salt setting
still provides improved overall performance while
operating in the salt/alkali ground condition.
Chapter 5 MXT 300 Controls