User's Manual

25
metal fragments make these two coils interesting.
The shape of these large coils should be the same
as with the other coils namely round or square. It is
also possible to build elliptical or dierent shapes
but this is only achieved at the expense of sensiti-
vity. Anyway, it is advisable to keep a distance of at
least 20 to 80 cm constantly between the coil and
the ground to reduce the amount of ground eects
to a minimum when using these very large coils.
In the near of power lines the amount of interfe-
rences produced will be higher than with smaller
coils and therefore again the sensitivity might be
reduced. The ground balancing system GND should
be changed to DEL in some cases using these large
coils because of the same reason. Some customers
use these large frame coils with two similar coils
mounted on each other at a distance of about 100
cm the same way as the dierential double frame
coil described below. A Z2 Y- adapter cable would
be necessary doing this. A test making sure that
both coils work in the same direction as described
before would also be necessary.
1M X 1M DOUBLE FRAME COIL KIT
This specially designed double frame coil kit basi-
cally consists of two 1m x 1m frame coils mounted
on each other at a distance of approximately 60
cm. Because of its ability to cancel out interferen-
ces from power lines or radio transmitters it can be
used in areas where single loop coils will suer from
false signals and poor sensitivity when electroma-
gnetic interferences are present.
The two coils receive the same amount of interfe-
rence but work in opposite directions. Therefore, al-
most any interference is subtracted from each other
while signals from the ground or metal objects will
pass to the electronics. It is important that the com-
ponents of the double frame kit are put together in
the right order as described below. The available kit
consists of the following components: two 1m x 1m
frame coils; four tubes 0,6m length; one Y adapter
cable with three connectors; two carrying straps.
The two 1m x 1m frames have to be mounted on
each other via the four tubes. Please make sure
that both frames go in the same direction, so that
the two yellow marks are pointing to each other
the same way! Afterwards the marked Y adapter
plug has to be connected to the lower frame which
points to the ground.
The upper second frame has to be connected to the
other adapter plug. The third connector has to be
connected to the electronics control box.
Note: It is advisable to make an operating test
where the lower search coil pointing to the ground
gives a signal when approaching to a metal piece
located on the ground and the upper coil will cause
a decay of the signal when a metal piece is appro-
aching from the top towards the coil. This could only
be tested with DEL = Delay settings and turned o
AUTO 0.
The sensitivity of this double frame coil is almost
the same as with the 1 m x 1 m single loop frame
coil. This coil does only suer from a very weak
sensitivity reduction of less than 10 % for very deep
and large metal objects. Especially when working in
the GND Ground mode it is very useful to work with
this particular search coil due to very stable and
therefore sensitive operation.