Fisher F4 - Control Panel; Sensitivity + and -; Auto Tune

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DD COIL CHARACTERISTICS
A DD coil is superior to a concentric coil, but sometimes requires a different
sweep technique.
Advantages are
1.
Better target separation
2.
Superior performance in highly mineralized ground
3.
Broader Sweep- cover more ground with each sweep
If you experience multiple responses on a shallow target, you can raise the
coil, or narrow the sweep over known targets to only intersect the center
section of the coil.
BOTTLE CAPS
The disadvantage of the DD coil is its propensity to classi-
fy steel bottle caps as coins.
If you hear a high tone in DISC Mode and believe that it
is a coin, make sure it is not a bottle cap using the fol-
lowing method.
1.
If a repeatable ID# around 68 to 72, then it
should be a dime or copper penny.
2.
If not in the range of 68 to 72, then:
a.
Sweep the back end of searchcoil over the
target. If tone changes from high to a low
tone, it is probably a bottle cap.
b.
Sweep searchcoil fast across
target.
1.
If tone and ID-value
drop, it is probably a
bottle cap.
2.
If a bottle cap, the faster
you sweep, the lower
the tone.
SWEET SPOT
The “center” of the DD-Coil is elongated (elliptical) from top to bottom of
the coil. With some practice you will find where the center of this ellipse
lies on your coil. Use this center point as a reference in pinpointing.
Sweep back end
of searchcoil over
suspected bottle cap.
(Low Tone = Bottle Cap)
The operating controls are as follows:
SENSITIVITY + AND –
These controls change the detector’s sensitivity; higher
settings enable detection of deeper targets. At power-
up, the detector is pre-set to 75% of maximum
sensitivity. At minimum, the sensitivity is 35% of
maximum. With each press of the + or – touch pads,
the sensitivity level is displayed on the bar graph on the
left of the display. Upon reaching the minimum or
maximum sensitivity setting, the detector will beep
twice.
While higher levels of sensitivity enable detection of deeper targets, operation at
high levels of sensitivity make the detector
more susceptible to electromagnetic
interference.
Higher sensitivity settings can also lead to false signals in difficult
ground conditions. Use lower sensitivity settings to suppress interference or false
signals from soil minerals when necessary.
If the detector “Chatters”, reduce sensitivity.
AUTO TUNE (All Metal)
Press this pad and “ALL METAL” appears on the display
This mode is a ground-balanced All Metal motion
search mode. This mode offers the maximum
amount of sensitivity under most ground conditions.
The searchcoil must be in motion to detect metal.
One monotone sound is emitted. No discrimination
or target identification is possible in this mode.
Use the
Sensitivity
or
Threshold
controls to
change the sensitivity or background hum. Maximum sensitivity to buried
metal objects is achieved with a slightly audible background hum.
To achieve an audible background hum:
1.
Press AUTO TUNE pad to enter this mode.
2.
Press
Sensitivity +
or
-
pads until you reach a desired setting.
This sensitivity setting may be the highest “quiet” setting, or you may hear
a faint background hum.
3.
Press
Threshold + or
-
pad until you reach a comfortable volume level.
The Sensitivity control works like a course adjustment in this mode.
The Threshold control works like a fine adjustment in this mode.
The AUTO TUNE Mode must be ground-balanced to eliminate interfering
signals from soil minerals. See the section on ground balancing for a
description of this procedure.
CONTROL PANEL
F4manual-SPREADS(24pg).qx_MF4B-F4manual 4/2/15 12:29 PM Page 8