Discrimination Mode - Fisher F75 SPECIAL EDITION User Manual

F75
LIMITED
Comprehensive Operating Manual & Guide to Metal Detecting
Capabilities And Limitations (continued)
GROUND BALANCING
To achieve maximum depth in any detection mode, as well as when using the PinPoint
feature, the F75 offers the ability to cancel out ground minerals either by manual adjustment,
or automatically using the FASTGRAB feature.
If you do not perform the ground balancing operation, the Discrimination mode will usually still
work fairly well, but the ALL METAL modes will not. The Pinpoint feature can be used for
pinpointing objects at moderate depth in most soils without prior ground-balancing.
The internal computer will not cancel saltwater, so when detecting on wet ocean beaches,
ground balancing must be done manually.
DISCRIMINATION
Discrimination refers to a metal detector's ability to ignore metal objects in selected categories,
especially iron and aluminum. This makes searching much more pleasant in an area with a lot
of metal trash. The F75 offers a wide variety of discrimination features which you can select
according to the search conditions and your personal preference.
DEPTH READING
The estimated Depth Reading displayed when pulling the PinPoint toggle is based on the
strength of the signal. It is calibrated to coin-sized objects. Smaller objects will read deeper
than they actually are, and large objects will read shallower than they actually are.
AIR TESTING
There may be times when you want to test or demonstrate the metal detector without sweeping it over
the ground, for instance, if not fully assembled, or if you are indoors. To air test, place the searchcoil in
a spot where the detector is stable and more than two feet away from any large masses of metal,
including the reinforcing steel usually present in concrete. If you are wearing a wristwatch or jewelry
on your hand or arm, remove it. Then, test or demonstrate by waving metal objects over the
searchcoil; wave objects briskly, several inches over the top of, and parallel to, the searchcoil.
Ground balancing cannot be tested or demonstrated in air unless you happen to have
appropriate specimens of iron minerals available.
SWEEP SPEED
The F75 is noted for its quick response. This gives it unsurpassed ability to locate and identify
good targets surrounded by trash. It also permits the user to sweep the searchcoil quickly in
order to cover more ground with very little risk of losing targets. In general, if you are
searching an area where the desirable targets are more than 8 to 10 inches deep, a faster
sweep speed will detect to a greater depth and yield more accurate target IDs.
CHECKING A TARGET
In order to most accurately verify a detected target with most other metal detectors, users will
narrow their sweep and loiter over the top of the target. The F75 is different. The F75's quick
response and advanced signal sampling system produces the most accurate target IDs with
deliberate (shoulder width) sweeps all the way across the target, even if there are other
targets nearby. If you check targets using sweep techniques learned on some other detectors,
you run the risk of getting less accurate target IDs. You can use the confidence level indicator
to improve your technique.
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Comprehensive Operating Manual & Guide to Metal Detecting

Discrimination Mode

The Discrimination Mode is used to eliminate trash metal objects from detection, e.g. nails,
aluminum foil, or pull-tabs. The searchcoil must be in motion for metal objects to be detected.
Discrimination incurs some loss of sensitivity to small or deep objects.
The F75 discrimination system is much improved over conventional discrimination systems,
and may function quite differently than other discriminators you may be accustomed to. In
older systems, the apparent sensitivity decreases as discrimination level increases. The F75's
sensitivity may increase as discrimination increases, depending on the process number and
notches being used. Therefore, do not use the discriminator to control sensitivity. First set the
discrimination level and notches to establish objects to detect or eliminate; then adjust
sensitivity downward to eliminate interference, or upward to "work into the noise," if preferred.
SENSITIVITY
This controls the signal gain, and is adjustable from 1 to 99. Unlike the All Metal modes, the
Discrimination mode is designed to operate silently. If you hear noise when there is no metal
present or when the searchcoil is not in motion, reduce the Sensitivity setting until the machine
goes quiet. NOTE: there is no interaction between the sensitivity settings of the All Metal
and Discrimination Modes.
The sensitivity system has two stages, 1-29 (low gain), and 30-99 (high gain). As you lower
sensitivity and cross the transition from 30 to 29, you may notice the background noise
increase. You may need to adjust to a setting of 29 or less to silence electrical interference, or
to prevent overload on highly mineralized ground or in saltwater. You may also notice a shift
in the ground balance setting over difficult ground conditions as you cross this transition.
DISCRIMINATION LEVEL
This is adjustable from 0 to 65, and controls the range of objects to be eliminated from
detection (discriminated out or rejected). Objects with numeric values below the selected
discrimination level will not be detected. NOTE: the numerical range that pertains to each
class of object is printed at the top of the visual display. To eliminate iron, a setting of 15 is
usually about right. A setting of 65 will eliminate aluminum trash and zinc pennies, but nickels
will also be lost, unless you notch-in nickels with the NOTCH feature.
To use DISC LEVEL
1. Highlight DISC LEVEL using the MENU button.
2. Rotate the SETTINGS knob.
As you rotate the knob, a number between 0 and 65 appears.
3. Press MENU when you reach the desired target discrimination value.
• If you do not press MENU, and let the display time-out, the last displayed value
will be stored as the discrimination value.
• All targets, up to and including the value selected, will be eliminated from
detection, unless notched-in.
5. A slash will appear over the target words being eliminated. Notice that two slashes
can appear over each word. The left slash represents the bottom half of the range; the
right slash represents the top half of the range. When you select a value within any
range, the slash will appear, even though all values within that range might not be
eliminated from detection. To recall the discrimination setting, press the MENU button
until you enter the DISC LEVEL feature.
F75
LIMITED
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