ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru [email protected]
11
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.
This may also lead to targets air testing as iron, as well as a false increase in
sensitivity when air testing
.
Remember that for every 1 degree of ground balance offset from the 0 or
neutral point we get a corresponding increase or decrease in the VDI scale for a
given target. IE a 1 ground balance will increase the VDI by +1.
For example, if you are air testing a large copper coin that would normally give a
VDI of +82 to +84 but is now air testing with a VDI of -86. The result is that the device
ground balance is set +10 to +12 degrees too positive for performing an accurate air test.
Balancing with a piece of ferrite is required before performing an "air test" of the
device. Put the device on a non-metal surface, turn on automatic ground balance mode,
count to three, then bring the ferrite to the center surface of the coil from a distance of
25-30 cm (10”to12”) to complete the balancing procedure. Puzzled? Let's make it easier:
Take a CD and pass it flatwise in front of the search coil
.
If the CD gives a vertical hodograph and VDI of 0 (+1 or -1), then the device is ready for
“air" tests.
If the VDI of the CD differs from these values, then in auto GB click (to enter manual
GB) and adjust the phase of the ground balance in the desired direction. When the VDI of
the CD is at 0 (+1 or
–
1) your device is ready for air testing
.
BALANCING PROCEDURE.
We would like to bring your attention to the automatic balancing procedure developed by
experienced users.
1.
Find a metal-free area. You can find it by the threshold tone response in RT mode.
On an unbalanced device there will be a response to the clean ground, however the
sound will be soft and "diffused", without a strong localization. While the sound
would be sharp and with a strong increase in sound above a metal object. Select an
area with no localized sharp threshold tone increase while swinging the search coil 5-
10 cm to the left and to the right above the ground. If there is no localized sharp
threshold tone increase then the area is suitable for balancin
g.
2. Having found the metal-free area, raise the coil 30-40 cm above the ground
press wait for 3 seconds, and move the coil to the ground smoothly but
not too slow.
Warning! Do not move the coil to the ground closer than 10% of the search coil
diameter (for the searchcoilØ26 cm – 2-3 cm). This is related to the change in the
pattern of the search coils physical interaction with the ground in what is called
the "Close Zone" and it may impact balancing accuracy resulting in false
responses in clean areas with high levels of sensitivity.
A short tone (Hum) signifies the completed balancing procedure. If there is no tone
or it does not sound during lowering, but sounds when moving up, repeat the procedure
with the same formula: 30-40 cm above the ground, 3 seconds, and then lower the coil to
the ground. Follow the ground vector on the screen during the process. Its shape should
be a strait, slightly trembling line, on the horizontal axis of the ground scale.
