ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru aka_md@mail.ru
27
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.
Use additional scans to more accurately identify the type of object by centering
above the target. Sweep the coil through the maximum signal area as accurately as possible
maintaining a constant distance between the coil and ground. For the same reason scan the
target with coil in the direction of the least amount of surface change in the ground. In this
case, the effect of soil will be minimal.
When the search coil interacts with a metal object
there may be a single tone burst or possibly several tone
bursts in rapid succession. Therefore one should pay
attention to the following.
When the detector responds
with a single short high tone and the signal level is rather
stable it is a good probability that the targets is not very
large and of a non ferrous nature at a depth of more than
5cm.
On the other hand if the detector gives a series of
short high tones (usually 3) then the targets is shallow and
in the so called near zone (less than 5cm). The Signal level
will also display a value of 50 or greater.
A series of two short low-pitched sounds indicates
that in the area of the coil is an extended ferrous object
(like a nail) located along the scanning direction. If the
object is located along the perpendicular plane of the scan
or the coil, the device will issue a single low-frequency
short tone.
Fig. 16
It is important to note that the DD sensor is characterized by a
complex pattern when interacting with metal objects close to the coil
or the near zone (signal levels greater than 80). Therefore when
trying to determine the target ID adjust the coil height to a level that
will give a signal strength of 30 to 60 in the Turbo mode and from 15
to 30 in the normal search mode.
In other words, if conditions allow, try to identify objects above the near the zone.
Let’s us discuss some of the challenges with the so-called “hot rocks”, (VDI greater
than +84). In order to better differentiate between "hot rocks" and relatively large flat non
ferromagnetic objects (Large copper or silver coins) with a VDI range of +78 to +86, the
device uses a special high pitched tone which is different from the usual tone indicated on
such non ferrous targets. If you desire the signal from "hot rocks" can be deleted by setting
the discriminator sector value with the right edge of the +86. However, the most effective
means of suppressing the audible reaction on hot rocks is to use the DHR algorithm (Disc.
of hot rocks). The risk from using discrimination settings to eliminate an audio response to
hot rocks is this. Due to effect of the ground valuable targets, whose vector angle is close to
that of hot rocks, can being missed. This risk is virtually eliminated by using the algorithm
DHR instead.
As you know, a particular problem for induction metal detectors is the identification of flat
