Fisher F75 SPECIAL EDITION User Manual page 24

F75
LIMITED
Comprehensive Operating Manual & Guide to Metal Detecting
PinPoint Feature
After a buried target has been located using the All Metal or Discrimination modes, you want
to pinpoint the exact location of the target in order to facilitate its recovery. Accurate target
pinpointing will minimize digging.
Activate the PinPoint feature by pulling the trigger switch located under the housing. Unlike
the motion All Metal and Discrimination modes, PinPoint does not require motion to detect
metal. PinPoint will detect objects while the coil is in motion and will continue to detect metal
if searchcoil motion stops over the target.
Ground Pick-Up
If you have not performed the ground balancing procedure, the PinPoint feature usually
causes the ground to sound off. This means that while pulling the pinpoint trigger, the audio
tone will get louder as you lower the searchcoil to the ground; this is called ground pick-up.
Since you want to hear the target, rather than the ground, we recommend first ground
balancing in order to eliminate ground pick-up. Alternatively, if you experience ground pick-up,
you may place the coil very close to the ground, off to the side of the target; then pull the
trigger, and raise the searchcoil slightly while passing it over the target.
How to Pinpoint
Position the searchcoil an inch or two (2.5-5cm) above the ground, and to the side of the
target. Then pull the trigger. Now move the searchcoil slowly across the target, and the sound
will indicate the target's location. As you sweep from side to side, and hear no sound at the
ends of the sweep, the target is located in the middle of that zone, where the sound is loudest
and the audio pitch is highest. If the sound is loud over a wide area, the buried object is large.
Use the PinPoint feature to trace an outline of such large objects.
Narrow It Down
To further narrow the field of detection, position the searchcoil near the center of the
response pattern (but not at the exact center), release the trigger, and then pull it again.
Now you will only hear a response when the searchcoil is right over the top of the target.
Repeat this procedure to narrow the zone even further. Each time you repeat the
procedure, the field of detection will narrow further.
Buy a Pinpointer
When you kneel down to unearth the desired object, you may find it frustrating as the object
may appear exactly like the surrounding soil. You may hold the object in your hand, and find it
necessary to pass a handful of dirt over the searchcoil to see if it contains metal. An easier
way is to use a handheld pinpointer. It is a probe-like device which is poked into the ground,
making close up pinpointing a snap, reducing digging time, and minimizing the size of the
holes you will dig. Fisher Research Labs offers the FPoint™ pinpointer, a robust and
inexpensive device designed for this purpose.
24
Comprehensive Operating Manual & Guide to Metal Detecting
LCD Visual Display
In normal operation, when the searchcoil passes over a metal object, the electrical signature
(2-digit I.D.) of the metal object is displayed on the numeric display for 4 seconds, unless
superceded by another detected object. On a given buried object, the number will bounce
around if the signal is weak or if the amount of ground mineralization is high.
At the top of the display, a block illuminates to indicate the classification of the object.
Target ID is provided in all three modes, and requires motion in all modes, including STAT.
NUMERIC TARGET I.D. (2-digits)
The following table shows the numbers typically associated with certain commonly
encountered nonferrous metal objects. Older silver U.S. coins usually read about the same as
their modern clad equivalents. Modern quarter-sized dollar coins like the Susan B. Anthony
and the Sacagawea read about the same as a quarter. Many Canadian coins are minted from
a magnetic nickel alloy which gives very inconsistent readings and may register as iron. Most
one-ounce silver bullion coins will fall into the same range as the modern U.S. $1 Eagle.
OBJECT TARGET I.D.
Most iron objects 4-12
foil from gum wrapper 16-25
U.S. nickel (5¢ coin) typically 30
aluminum pull-tab 33-55
aluminum screwcap 60 - 70
zinc penny (dated after 1982) typically 60
aluminum soda pop can most often 63-69,
but can vary widely
copper penny, clad dime typically 70
U.S. quarter (25¢ coin), clad typically 80
50¢ coin, modern clad typically 86
old silver dollar coin typically 90
US silver Eagle $1 coin typically 91
PROBABLE TARGET I.D.
The probable target ID zones at the top of the LCD display represent the signal ranges
produced by various coins and types of metal objects. When a metal target is detected, the
microcomputer analyzes the signal and categorizes it based on what kinds of metal objects
usually produce that kind of signal. The microprocessor then displays a rectangle-like icon
along the top of the LCD screen above the corresponding category.
For instance, if the detected signal fits within the parameters usually exhibited by zinc pennies,
the microcomputer will categorize the signal as "zinc penny". The LCD screen will then
illuminate the block above "ZINC"
Copper pennies (pre-1982) will usually register in the DIME zone.
Most gold jewelry is small, and will tend to read in the 16-55 range. Silver jewelry usually has
more metal in it and therefore tends to produce higher readings.
F75
LIMITED
25