16
ELECTROMAGNETIC
INTERFERENCE
The principle use for the
Sensitivity Control is to
eliminate Electromagnetic
Interference (EMI).
A hobby metal detector is an
extremely sensitive device;
the search coil creates its
own magnetic field and acts
like an antenna. If your
detector beeps erratically
when the search coil is
motionless, the unit is probably detecting another electromagnetic field.
Common sources of EMI are electric power lines, both suspended and
buried, motors, and household appliances like computers and
microwave ovens. Some indoor electronic devices, such as dimmer
switches used on household lighting, produce severe EMI and can cause
the detector to beep erratically. Other metal detectors also produce their
own electromagnetic fields; so if detecting with a friend, keep two metal
detectors at least 20 feet apart.
If the detector beeps erratically,
REDUCE THE SENSITIVITY
by
pressing the Sensitivity
▼
Pad on the left of the control panel.
SEVERE GROUND CONDITIONS
A secondary use for the Sensitivity Control is to reduce false detection
signals caused by severe ground conditions. While your Discovery 3300
contains circuitry to eliminate the signals caused by most naturally
occurring ground minerals, 100% of all ground conditions cannot be
anticipated. Highly magnetic soils found in mountainous and gold-
prospecting locations can cause the detector to emit tones when metal
objects are not present. High saline content soils and sands can
sometimes cause the detector to false.
If the detector emits false, non-repeatable, signals, REDUCE THE
SENSITIVITY.
MULTIPLE TARGETS
If you suspect the presence of deeper targets beneath a shallower target,
reduce the sensitivity to eliminate the detection of the deeper targets, in
order to properly locate and identify the shallower target.
SENSITIVITY ADJUSTMENT
