Minelab GPX-4500, Instruction Manual

Page: 14 / 55

22 23 Detector Sounds
Target Response
(Metal Object Response)
This is a change in the tone (pitch)
and volume of the Threshold
when a target is detected and not
discriminated (rejected).
Threshold (Background sound)
This is the background sound produced
by the detector. When a target is
detected, the Threshold
(pg. 34)
changes in volume and pitch. Listen to
the Threshold carefully. Concentration
is an important part of detecting.
A very deep or small target may only
cause a very small change to
the Threshold.
Electrical Interference
The detector may produce random
sounds when the coil is motionless.
These will not be target signals, but
signals caused from the surrounding
environment. The GPX-4500 has a Tune
(pg. 32) function to overcome electrical
interference.
Note: The GPX-4500 is a
‘motion’ detector. This
means it must be moving
over a target to detect it.
Detecting Basics
The GPX-4500 will perform at its best when the coil
is kept close and parallel to the ground at all times.
This will increase the detection depth and target
response to small objects.
A variation in coil height at the end of each swing
may cause confusing sounds and reduce detection
depth; an even flat sweep is desirable.
Practise sweeping the coil over the ground in a
side-to-side motion, while walking forward slowly at
the end of each sweep. Slightly overlap the previous
sweep to ensure full ground coverage. An average
sweep speed is four seconds from left to right to left.
Ground Noise
Certain minerals may cause the
detector to produce various sounds;
often referred to as false signals. The
GPX-4500 has an automatic Ground
Balance function to overcome ground
noise.
(pg. 38)
Blanking
When the detector is in Iron Reject
mode and sweeping over a ferrous
target the Threshold ‘blanks’ (becomes
silent), indicating that a target is
located underneath the coil but has
been rejected. Blanking
(pg. 79)
is a
useful way of distinguishing between
desired and undesired targets.
Low Battery
When the battery voltage (pg. 55) is
low, a series of alarm signal pulses are
given at one minute intervals.
Tip: When using a Monoloop coil more overlap is
required to ensure that targets at maximum depth are
not overlooked (see pg. 90 for a diagram showing coil
search patterns).