White’s Electronics MXT - Manual (Page 19)

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Another example of when Lock would be used is if
a particular mineralized rock or patch creates
difficulties in searching an area. A hard rock mine
for example with a low mineralized base rock and
random high mineralized rocks or patches. Place
the TRAC control in the Ground position and
balance "pump the search coil" over a representa-
tive sample of the high mineral rock or patches.
Then Lock in that ground rejection setting "place
the TRAC control in the Lock position". The entire
area can then be searched without the distraction of
the inconsistencies 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 rejection
against salt/alkali slightly overlaps the lower end of
the conductive target (metal) range. In other words
if you ground balanced against significant salts,
some loss of sensitivity to lower conducting metals
(metals low on the VDI target scale) can be ex-
pected. 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 ground rejection system is capable, in both
the Ground and the Salt settings, of considering
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
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 first
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
appear low on the VDI scale. The Ground TRAC
setting will not balance nor track into the nonfer-
rous 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 Controls
Chapter 5 MXT Controls