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Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.
To change any of these
settings press the appropriate
button. The value of the selected
option is highlighted on the screen
with a rectangle around the
appropriate value.
Press the button
Fig. 6
Or to set the required
value. In order to exit the
parameters simply click the button again. When neither the RT, ST or Volume
values are displayed on screen - the buttons and will now act as
on / off modes for the Turbo and S-algorithm, (see below)
GROUND BALANCE
Balancing the device to the ground is the single most important part of the
device settings for accurate search results. Improper ground balancing can result in
decreased responses to targets and may result in instability as well as an increase in false
ground signals.
To explain the basic physics behind the ground balance procedure. Every object
has its own shape, conductivity and magnetic component, which together are called the
VDI (Visual Digital Index). Remember that the VDI is the angular response that is
numerically equal to the angle of deflection of the signal vector time curve (hodograph
display) on the vertical axis. The soil, or ground, depending on the degree of
mineralization (presence of iron oxides) imposes its signal on the target signal thus
changing the VDI upscale. This is especially true on small or deep targets, as well as large
highly conductive targets (copper, silver, aluminum). This can actually push these high VDI
targets up and over into the high negative VDI range known as “VDI wrap around”. To
minimize this effect, it is crucial to perform a proper and accurate ground balance
procedure.
The basic objectives of balancing:
1. Make the soil 'invisible' to the instrument, i.e. exclude false signals
from the ground where there is no target.
2. Install the correct (standardized) reference system number for the VDI.
When receiving a signal from both the ground and a detected object the
detector must subtract mathematically the signal from the ground in
order to display a correct VDI indication of the detected target
Keep in mind that when performing “air tests” inside after the detector has been
previously balanced in soil may result in incorrect VDI readings. This is due to the
correction factor for the VDI previously set in the last ground balance. This may result in
the loss or “invisibility” of large aluminum, silver and copper targets. If the ground setting
is too positive the VDI will be offset positive and vice versa if the ground balance is
negative.
