User Manual

28 13
TEKNETICS
C
omprehensive Operating Manual & Guide to Metal Detecting
TEKNETICS
C
omprehensive Operating Manual & Guide to Metal Detecting
GROUND CANCELLATION (continued)
MANUAL GROUND CANCELLATION (continued)
The Fe
3
O
4
bar graph on the LCD display indicates the amount of magnetic mineralization. The
searchcoil must be in motion to measure Fe
3
O
4
. The most accurate measurement is obtained
by pumping the searchcoil, as in the Ground Cancellation procedure.
The two-digit G.C. Phase number displayed on the LCD indicates the type of ground mineralization.
Some typical ground mineralization types are:
0–10 Wet salt and alkali
5–25 Metallic iron (very few soils in this range. You may be balancing over metal)
26 – 39 Very few soils in this range — occasionally some saltwater beaches
40 – 75 Red, yellow, and brown iron-bearing clay minerals
75 – 95 Magnetite and other black iron minerals
When manually ground canceling, try to “feel out” a spot on the ground to make sure there is
no metal present. In order to avoid locking onto metal, the computer will not cancel ground
where the numbers are less than 40. Where the ground reads less than 40, manual ground
cancellation is required.
To perform the Manual Ground Cancellation operation, do the following:
1. Select the MANUAL G.C. function
The legend G.C. PHASE appears.
The present ground cancellation setting is
displayed (0-99).
The message PUMP COIL TO G.C. will
appear.
2. 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.
3. Turn the SETTINGS KNOB to adjust the level.
goal is to eliminate the sound as the coil is being
pumped over the ground. In some soils, the
sound is not completely eliminated; rather, the
audio feedback is the same both when lowering the searchcoil to the ground, and
when lifting the searchcoil off of the ground.
If the ground cancellation adjustment is incorrect, there will be a difference in the sound as the
searchcoil is either moving toward or away from the ground. It sounds like you are either
pulling the sound out of the ground, or pushing the sound into the ground.
• If the sound is louder as you raise the searchcoil, increase the ground cancellation setting.
• If the sound is louder as you lower the searchcoil, reduce the ground cancellation setting.
•
NOTE: Experienced users often prefer to adjust the ground cancellation to get a weak but
audible response when lowering the searchcoil. This is called adjusting for positive response.
GC PHASE 90
SEARCH TECHNIQUES (continued)
Estimating Target-ID
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 T
2
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 visual ID and the discriminator are independent systems which analyze different sets of
signals. Therefore what you hear, or do not hear, provides additional information regarding
Target-ID. For instance, if discrimination is set at 40, 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 40.
The T
2
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
T
2
’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 electrical interference or internal
circuit noise. 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 T
2
allows you to shift operating frequencies to avoid electrical interference. See the
Frequency Shifting section on page 21 for information about this technique.
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