White’s Electronics MX5 - Manual (Page 16)

Page 16
MX5
Owner’s Manual
Ground Balance & Tracking
Most soils contain iron-based minerals which affect metal
detectors. We generally call this mineralization. These ferrous
minerals usually don’t respond like metal targets but still upset
the delicate balance required of VLF detectors. In fact, the sig-
nal strength from ground minerals can many times greater than
that of an average buried coin.
It is possible to largely null out the ground signal and leave
only target signals. This is done with a combination of special
tuning in the receiver plus filters. The tuning portion is what we
call ground balance. Some detectors have a fixed (preset)
ground balance which is optimal for one type of mineralization;
in other types of ground it may not be optimal and will result in
loss of depth. The MX5 has a variable ground balance with the
ability to automatically track changes in soil mineralization.
This system (called AutoTrac
® ) keeps the MX5 tuned for opti-
mal performance in most ground conditions and results in better
detection depth.
Most ferrous mineralization produces a response with a
VDI of -93 (for pure ferrite) up to perhaps -88 or so. This is at
the extreme end of the ferrous (iron) region. Most small iron
targets (nails and so forth) reside in the middle of the ferrous
region. To prevent tracking to iron targets the AutoTrac
® system
has an upper limit on the track range of -88 (VDI). Sometimes
we draw the VDI scale as a semicircle, with ferrous (-95 to 0)
on the left and non-ferrous (0 to +95) on the right; we can use
this to show the normal range of ground tracking:
-95 +95
0
Normal Track Range
F
e
r
r o
u s
N o
n -
F e
r
r
o
u
s