False Signals And Chatter - Teknetics T2 Operating Manual And Manual

MT2E-TekneticsMANUAL.qx6_MT2E manual 10/20/14 11:10 AM Page 14
TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
GROUND CANCELLATION (continued)
MANUAL GROUND CANCELLATION (continued)
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.
The 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
• If the sound is louder as you raise the searchcoil, increase the ground cancellation setting.
pulling the sound out of the ground, or pushing the sound into the ground.
• 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.
The purpose of ground cancellation is to adjust the metal detector to ignore ground minerals.
Positive and Negative Response
If the adjustment setting is off, ground minerals will give either a positive or negative response,
depending on which direction the adjustment is off.
If the G.C. setting is too high a number, the response of minerals will be positive. This means that
POSITIVE RESPONSE
when the searchcoil is lowered to the ground in PinPoint or All Metals Mode, the sound will get
louder as the searchcoil approaches the ground. The sound will grow quieter as the searchcoil is
raised. What, if anything, you hear in Discrimination Mode depends on the discrimination setting.
When searching in All Metals Mode, if ground cancellation is properly set to cancel the ground, and
you sweep over a positive hot rock, the rock will give a "zip" sound similar to that of a metal object.
If the G.C. setting is too low a number, the response of minerals will be negative. When the
NEGATIVE RESPONSE
searchcoil is lowered to the ground in PinPoint or in All Metals Mode, the machine will be silent.
In All Metals Mode, the machine will sound off as the searchcoil is lifted away from the ground.
What you hear, or do not hear, in Discrimination Mode will depend on the discrimination setting.
When searching in All Metals Mode, a negative hot rock will produce a "boing" sound after
passing over it, making it difficult to tell where it is located. It will not have the sound and "feel"
of a metal object.
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Comprehensive Operating Manual & Guide to Metal Detecting
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
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 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
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.
T 2

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 can be caused by power lines, appliances, computer equipment, cell
ELECTRICAL INTERFERENCE
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 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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