Comprehensive Operating Manual & Guide to Metal Detecting
Comprehensive Operating Manual & Guide to Metal Detecting
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33
F75
F75
Controls (continued)
The
F75
has two controls on the front panel, MENU and SETTINGS.
MENU Pushbutton
(Red button on right of the front panel)
Push the MENU button to:
1. Step through the menu selections on the display.
With each push of the button, the next menu selection will be highlighted.
The SETTINGS knob then allows you to change values for the highlighted selection.
2. Recall the last setting which you adjusted.
After you have adjusted a setting, an indicator will remain highlighted next to this menu
selection. One push of the button will recall that selection and display the stored value.
This recall function is useful for a value you want to adjust frequently, such as the
ground balance setting. In order to adjust a stored value with the SETTINGS knob, you
must first press the MENU button to reactive the user interface.
SETTINGS Knob
(On the left of the front panel)
Rotate the SETTINGS knob to:
1. Change the setting (or value) of the highlighted menu selection you have chosen.
2. Select the operating MODE when the top line of the menu is highlighted.
When used to switch back and forth between the DISCRIMINATION mode and ALL METAL
modes, the detector changes modes as soon as the corresponding selection is highlighted.
The All Metal modes are used to detect all metal objects, including small or deep objects.
Use the Discrimination mode to ignore trash metal such as nails, foil, or pull-tabs.
NOTE: When the menu selection
highlight disappears,
the
SETTINGS knob is deactivated.
If settings values do not change when the SETTINGS knob is rotated, press the MENU button
to reactivate the user interface.
TRIGGER SWITCH
(Under the display in front of your hand)
While the trigger is
pulled
back, metal objects are temporarily detected without the need for
searchcoil motion. This aids in pinpointing the exact location of objects which were found
while searching in the Discrimination or motion All Metal modes.
When in static all metals mode, pulling the trigger zeroes the audio threshold to the signal
level currently preset. If the searchoil is up in the air away from metal, this maneuver corrects
for threshold drift due to temperature changes.
When the trigger is
pushed
forward, FASTGRAB automatic ground balancing is activated. The
internal computer measures the magnetic properties of the soil in order to cancel interference
from naturally-occurring minerals in the ground. After the detector measures the soil in this
manner, the detector then uses this information to control operation in both the All Metal and
Discrimination search modes. FASTGRAB can be used at any time during operation.
Search Techniques (continued)
Estimating Target I.D.
With a single sweep over a target, you will usually see a 2-digit target ID displayed on the LCD.
Repeated sweeps back and forth over the target may cause the 2-digit target ID values to change
with each sweep of the coil; this may seem inconsistent with your discrimination setting. These
variations and inconsistencies provide important clues regarding the identity of the buried object.
Most metal detectors have difficulty properly identifying steel bottle caps, and the
F75
is no
exception. Steel bottle caps will often read in the coin range, at the high end of the scale.
The ID number you receive from a buried coin will usually be consistent regardless of sweep
speed or angle. The readings from a steel bottle cap will tend to bounce around a lot more,
especially with variations in sweep speed or angle. By paying attention and taking this into
account, you can minimize the number of bottle caps you dig.
The information provided by the Visual Target ID may be different than the detector’s Audio
Feedback because the visual and audio systems are independent of one another. The internal
signals and algorithms controlling the Visual and Audio output are different. Therefore what
you hear, or do not hear, provides additional information regarding target ID. For instance, if
discrimination is set at 12, and most sweeps result in no visual target ID, the target is most likely
iron even though the majority of the ID numbers will be greater than 12.
The
F75
has a tendency to
up-average
nonferrous targets in the proximity of iron, indicating ID
numbers higher than would be obtained in an air test. This tendency is connected with the
F75’s
enhanced
see-through
ability – that is, the ability to find valuable targets in an area
where there is a lot of iron trash.
False Signals and Chatter
At times the detector may beep when there is nothing there, or it may seem like there is
nothing there. There are five major causes for this: electrical interference, nuisance buried
objects, ground minerals, hot rocks, and sensitivity set so high that internal circuit noise is
audible. The problem can usually be corrected by reducing the sensitivity setting, but
sometimes other measures can also be taken.
ELECTRICAL INTERFERENCE
Electrical Interference can be caused by power lines, appliances, computer equipment, cell phones,
fluorescent and vapor type lamps, household light dimmers, other nearby metal detectors, electric
fences, radio transmitters, and electrical storms. If you get abnormal noise while holding the
searchcoil motionless in the air, the cause is either electrical interference or internal circuit noise. If
it is electrical interference, by walking around with the metal detector, you can often follow the
signal and track it back to the offending device; simply turn the device off, or come back at another
time when it may be off. If the interference is from power lines, you might try another time of day.
Interference on power lines is usually caused by something connected to them which may be idle
in the evenings or on weekends. If the interference is from a communications or broadcast
transmitting antenna, reducing the sensitivity is usually your only recourse.
The
F75
allows you to shift operating frequencies to avoid electrical interference. See the
Frequency Shifting section for information about this technique.
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