Fisher Labs F5 Operating Manual page 13

GROUND BALANCING –
Understanding ground conditions assists the user in setting up the
machine, knowing when to readjust ground balance, and in
understanding the responses of the machine while searching.
Fisher F5 provides two kinds of ground data: 1 1 . . the amount of
mineralization (the greater the amount of mineralization, the greater the
loss of detection depth & ID accuracy; this loss is more pronounced in
Discrimination Mode) 2 2 . . the type of mineralization (which affects mostly
where the ground balance should be set).
F F e e O O B B A A R R G G R R A A P P H H
3 3 4 4
The Fe O 4-segment bar graph indicates the amount of ground
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mineralization, independent of type, expressed as an equivalent volume
concentration of magnetite (Fe
sensitive to motion and will give the most accurate readings if you
"pump" the search coil up and down several times over the ground. The
presence of metal or "hot rocks" will cause the readings to be inaccurate.
If you stop moving the search coil, the bar graph will go blank.
I I N N D D I I C C A A T T I I O O N N
H — HIGH
M — MEDIUM
L — LOW
VL — VERY LOW
none - -
Magnetic susceptibility is expressed in micro-cgs units. In a salt water
environment in the absence of iron minerals, the bar graph indicates
relative electrical conductivity.
In soils with greater than 4,000 micro-cgs units magnetic susceptibility, the
signal from the soil may saturate ("overload") the circuits. This will not harm
the detector but the machine will not be usable in that condition. The
solution is to hold the search coil several inches above the soil surface so
it isn't "seeing as much dirt". By listening and watching you will know how
high you need to hold the search coil in order to avoid overload.
The highest magnetic susceptibilities are usually found in soils developed
over igneous rocks, in alluvial 'black sand" streaks on beaches, and in
red clay soils of humid climates.
The lowest magnetic susceptibilities are usually found in white beach sands
of tropical and subtropical regions, and soils developed over limestone.
Technical Information
O ). It updates every second.
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% % F F e e O O
3 3 4 4
0.4 - 1.6
0.1 - 0.4
0.025 - 0.1
0.006 - .025
less than .006
S S U U S S C C E E P P T T I I B B I I L L I I T T Y Y
1,000 - 4,000
250 - 1,000
60 - 250
15 - 60
less than 15
The
It is
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