Fisher Research Labs Gold Bug, Owner'S Manual

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GROUND BALANCING -Technical Info
Fe
3
O
4
BARGRAPH
The Fe
3
O
4
7-segment bar graph indicates the amount of ground mineralization,
independent of type, expressed as an equivalent volume concentration of
magnetite (Fe
3
O
4
). It updates every second. It is sensitive to motion and will give
the most accurate readings if you pump the searchcoil 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 searchcoil, the bar graph will go blank.
INDICATION RELATIVE % Fe
3
O
4
SUSCEPTIBILITY
MINERALIZATION
7 Bars High over 1 over 2500
2 to 6 Bars Medium .026 - 1.0 61 - 2,500
1 Bar very Low 0.006 - .025 15 - 60
none -- less than .006 less than 15
Magnetic susceptibility is expressed in micro-cgs units. In a saltwater environment
in the absence of iron minerals, the bar graph indicates relative electrical conductivity.
In soils with greater than 10,000 micro-cgs units magnetic susceptibility, the
signal from the soil may saturate, or overload, the circuitry. This will not harm
the detector but the machine will not be usable in that condition. The solution
is to hold the searchcoil several inches above the soil surface so it is not “seeing
as much dirt.” By listening and watching you will know how high you need to
hold the searchcoil 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.
OPERATING IN ALL METAL MODE
The All Metal Mode is more sensitive than the Discrimination Mode, and is used to
find all types of metal objects in the ground. The searchcoil must be in motion for
objects to be detected.
Ground Grab ® Computerized Ground Balancing
Naturally occurring minerals in soil look like metal to a metal detector, so you want to
cancel out
this mineral signal coming from the ground, and only detect the signal from
metal objects in the ground.
So before using your detector, set it in All Metal Mode and perform the automatic
ground balancing procedure. Press-and-hold the Ground Grab
®
Computerized
Ground Balancing button while pumping the searchcoil up and down over the
ground. release the button when the sound evens out. The GND BAL number on the
bottom right of the screen is the detector’s internal setting which cancels out the
minerals in the ground. Different soils in different areas will require different GND BAL
settings, so balance to ground before you search.
Refer to the Ground Balancing section of this manual for a more in-depth explanation.
Setting the Controls
As you adjust any of the controls, notice that the values on the bottom-right of the
display indicate the settings of the value you are changing.
If you are new to metal detecting, start with the GAIN and THreSHOLD controls at a
low enough setting that you do not hear too many unwanted sounds, like warble or a
loud hum. Set the GAIN at the 12:00 position, or less. Then set the THreSHOLD to a
position where you hear a very slight background hum, or if you prefer, dial the control
just left of that position to a setting where the detector is silent.
Unwanted Noise
read the section on electromagnetic Interference (eMI).
The Gold Bug
®
is a highly sensitive device.
It is intended for use outdoors. Indoor operation will subject it to interference from a
wide variety of devices in the home or office.
Sweeping the Searchcoil
As you sweep the searchcoil over the ground, try to keep the searchcoil parallel to the
ground.
Avoid lifting the searchcoil at the end of your sweeps.
Operating in All Metal Mode continued on next page