Fisher Research Labs Gold Bug, Owner'S Manual

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GROUND BALANCING
What is Ground Balancing?
Why do I need to Ground Balance?
All soils contain minerals. Signals from ground minerals are
often tens or hundreds of times stronger than a buried metal
object. The magnetism of iron minerals, found in nearly all soils,
causes one type of interfering signal. Dissolved mineral salts,
found in some soils, are electrically conductive, causing another
type of interfering signal.
Ground Balancing is the process by which the
metal detector cancels the unwanted signals
coming from the ground minerals while still
detecting the signals from buried metal objects. This
is accomplished by matching the detector’s
ground balance setting to the phase of the
ground signal.
When the detector is calibrated to the soil, the
result will be deeper target detection, quieter
operation, and more accurate Target Identification.
How to Ground Balance your detector:
Ground Balancing procedure with the Ground Grab
®
Computerized Ground
Balancing touchpad.
1. Turn the detector on and set GAIN at the 12:00 position.
2. Click on the right knob to the ALL MeTAL Mode.
3. rotate the THreSHOLD control knob to the point where you hear a slight
background hum.
4. Sweep searchcoil across the ground to find a clear patch of ground with
no metal present.
5. Press and hold the GrOUND GrAB
®
Computerized Ground Balancing
touch pad, and pump searchcoil over the clean ground. See illustration
above.
Pump searchcoil from within 1” of ground to 6”- 8” above ground.
6. When the GND PHASe settles down to only 1 or 2 numbers in variation,
release the GND GrAB button while still pumping the searchcoil. Note that
the audio response to the ground changed and “evened Out” when you
released the button. Also note that the GND BAL value changed. After
balancing, you can hunt in ALL MeTAL... or return to Disc Mode.
The most accurate GND PHASe value is the value displayed when “pumping”
the searchcoil over the ground in an area free of metal.
Ground Balancing continued on next page
Pumping coil
to ground
balance with
Ground Grab
®
Computerized
Ground
Balancing
button.
Using PINPOINT
Press-and-Hold the Pinpoint button to narrow down the location of a buried metal object.
Pinpoint is a mode of detection which does not require the searchcoil to be in motion.
A motionless searchcoil held over a metal object will induce a hum; volume and
pitch of the hum increase with target strength.
The approximate target depth, in inches, will be indicated in the center of the screen.
The depth scale is calibrated to coin-sized objects.
relative depth is indicated for larger or smaller objects.
Upon releasing the button, you will return to the motion Discrimination detection mode.
If you keep the Pinpoint button depressed for a long time, the audio tone may begin to drift.
If you plan to search like this, release and re-press the button periodically to avoid
drift. Drift may result in a loudening sound or a reduced sensitivity with no sound.
See the manual section on Target Pinpointing for how to narrow down a target’s location.
This technique is indispensable as long-buried metals can look exactly like the
surrounding soil to the naked eye. If you are not adept at pinpointing, digging up a
small metal object can be very frustrating. So learn how to narrow-it-down.
READING THE DISPLAY
TARGET-ID
each time you pass the searchcoil over a metal object, a 2-digit value will appear in
the center of the display. See the manual section on Target Identification for a better
understand of these values.
Three segments will simultaneously appear above the arc at the top of the screen.
This represents the same Target Identification, but displayed graphically within the scale.
TARGET SCALE
This display works as in the All Metal Mode.
The arc across the top classifies metal objects.
each time a target is detected three segments will illuminate above the arc.
The segments will remain illuminated for three seconds.
This indication shows the approximate classification of the buried metal object.
See the section on Target Display for a more detailed explanation.
Iron is on the left. U.S. dimes and quarters are to the far right.
In an air test, gold indicates right of center -- the larger the gold piece, the
farther to the right.
In the ground, the ID of gold may jump around with each pass of the coil.
SIGNAL
each time a target is detected, bars will illuminate on the bottom left showing the
strength of the target’s signal.
If all 7 bars illuminate, the target signal is strong.
This may be a large metal object.
Or it may be a coin-sized metal object close to the surface.
If only a few bars illuminate, the target signal is weak.
This may be a deeply buried object, even a big one.
Or it may be a very, very small metal object, close to the surface.
The depth of a coin-sized object can be confirmed using Pinpoint.
OPERATING IN DISCRIMINATION M ODE