User's Manual

12 29
TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
GROUND CANCELLATION
What is Ground Cancellation?
All soils contain minerals. Signals from ground minerals are often tens or hundreds of times
as strong as the signal from 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 Cancellation is the process by which the metal detector cancels the unwanted ground
signals while leaving signals from buried metal objects intact. This is accomplished by
establishing the detector’s internal Ground Phase setting; this setting is calibrated to the soil
and eliminates the ground minerals’ signal.
When the detector is calibrated to the actual soil condition, the result will be
deeper target detection, quieter operation, and more accurate Target
Identification. This calibration, or Ground Cancellation, can be accomplished
automatically with the detector’s internal computer, by pushing the Trigger
Switch forward, or manually in the All Metal menu.
The ground cancellation setting carries through into both All Metal and
Discrimination Modes. In Discrimination Mode, the ground signal is generally
inaudible unless the discrimination setting is 0.
AUTOMATIC GROUND CANCELLATION PROCEDURE
(FASTGRAB™)
1. Find a spot of ground where there is no metal present.
2. Hold the detector with the searchcoil about one foot
above the ground.
3. Push the TRIGGER SWITCH forward with your index
finger.
4. Physically pump the searchcoil and detector up and down over
the ground. Lift it about 6 inches above the ground and lower
it to within 1 inch of the ground, about once or twice a
second.
5. A 2-digit value will appear on the display. This is the
Ground Phase setting.
If the detector’s internal computer is
unable to cancel the ground signal, the
message
CAN’T GC will appear; find
another spot of ground and try again.
THE MENU SYSTEM (continued)
If you press the MENU button or rotate the SETTINGS knob while the machine is in normal
operation, the user interface will return to the last menu feature setting. This feature allows
you to have quick access to a function that you want to adjust frequently.
SEARCH TECHNIQUES (continued)
NUISANCE BURIED OBJECTS
In some areas there is a lot of metallic trash which produces weak signals. These could
include deeply buried objects, little bits and pieces of rusty iron and corroded foil. These items
can be detected, but are difficult to pinpoint due to their depth and small size. When you dig
and find nothing, it may seem like the machine is beeping at nothing even though there is
actually something there. The best solution is usually to reduce sensitivity.
If searching a very trashy area and unwanted signals are a problem, search with the
searchcoil 2 inches away from the ground. Trash objects very close to the searchcoil will
sometimes not be completely eliminated, even when the discrimination setting should have
eliminated the target.
Metal detectors are designed to see one metal object at a time. Where there are two iron
objects near each other, the detector can be fooled into thinking that the gap between them is
nonferrous metal. This is a common condition where a wooden building has burned or been
torn down, and the site is littered with nails. A signal from a nonferrous metal object such as a
coin will usually be repeatable, whereas a false
positive signal resulting from multiple or oddly
shaped iron objects will seem to wander around and even to vanish. Experienced detectorists
call these
non-repeating signals and usually do not bother digging them since nonrepeating
signals are almost always trash.
GROUND MINERALS
Conductive mineral salts usually produce broad signals which will not be mistaken for a
metallic object. Common causes are concentrations of mineral fertilizer, spots where
evaporation has concentrated naturally occurring mineral salts, residue from de-icing salts,
and urine from livestock. Unless dry, “cow pies” can sound off like they are metal. Ocean
beaches have salt water—that subject is discussed elsewhere in the manual.
In spots where there has been intense fire, such as a campfire site or where a stump was
burned during land clearing, the soil minerals may be altered by oxidation so that their ground
cancellation setting is lower than that of the surrounding soil. In such cases, search slowly and
change the G.C. setting as frequently as necessary.
In some areas, electrically conductive industrial minerals such as smelter coke, slag, and
charcoal have been dumped or used as landfill. Individual lumps of these materials can
usually be quieted by reducing sensitivity and searching with a discrimination level of at least
50. However, where the ground consists primarily of such materials, you may not be able to
search quietly. In that case, do not dig unless a signal is crisp and repeatable.
Electrically conductive natural minerals such as graphite, graphitic slate, or sulfide ore
minerals are rarely encountered except when gold prospecting. When gold prospecting, you
need to be able to hear everything, and you can expect to dig conductive minerals that turn
out not to be gold. In a given locality you may learn to recognize what type of rocks these
minerals are found in, and to ignore them if people in the area say that gold is not found in
rocks of that type.