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TARGET DEPTH
The device provides an estimated target depth according to the signal strength. In the
pinpoint mode, estimated target depth is shown on the display in cms (or inches - please
see below for details) while getting closer to the target.
Depth detection is adjusted presuming that the target is a 2.5cm (1'') coin. Actual depth
varies according to the size of the target. For instance, the detector will indicate more
depth for a target smaller than a 2.5cm (1'') coin and less depth for a larger target. In reality,
pinpoint procedure is not intended for depth determination but exact location determina-
tion. Therefore, it is recommended that the depth indicator on the display is used for deter-
mining the proximity to the target.
IMPORTANT!
If you want the target depth to be displayed in inches instead of cms please
do the following: While the device is off, press and hold the SELECT and EXPERT buttons
simultaneously and turn the device on. ''In'' will be displayed. To switch back to cms, you
need to turn the device off and then repeat the above procedure. While the device is initial-
izing, ''SI'' will be displayed.
LARGE OR NEAR-SURFACE TARGETS
Targets which are near the surface may give multiple different signals to the device. If you
suspect a target near the surface, lift the search coil and swing it more slowly until a single
signal is received. Also, if there is a large target near the surface it may cause an overload
in the search coil and the device starts to generate a continuous sound which resembles
a siren. “Overload” message is shown on the display simultaneously. In such a case, lift the
search coil up until the message disappears.
FALSE SIGNALS AND REASONS
Sometimes, the device may produce signals which are similar to a target signal although
no metal target is present. There are various reasons for the false signals received by the
device. The most common ones are ground mineralization or rocks with high mineral con-
tent, surrounding electromagnetic signals, operation of another nearby detector, rusted
or corroded iron or foil in the soil, gain or threshold values set too high.
Surrounding electromagnetic signals can be eliminated by reducing the gain. If another
detector is operating nearby, you may attempt to shift the frequency or perform your
search at a distance where no interference occurs. If these do not improve the situation,
you may try changing the operating frequency (5kHz/14kHz/20kHz) of the device. For
ground mineralization or rocks with high mineral content, and gain and threshold set too
high, please read the related sections.
MAGNETIC MINERALIZATION INDICATOR
The Magnetic Mineralization Indicator consists of 5 levels. The indicator is shown empty at
low mineral levels during search and at start up. In areas where the magnetic mineral level
is high, the indicator level increases according to the intensity. This measurement can be
summarized as the level of magnetic property and intensity of the ground. Simply, if you
are working in an area which contains intense and magnetized minerals, the level will be
high. If you are working on a less intense ground, the level will be low.
This measurement is important from two aspects. First, on grounds with high magnetic
mineralization, search depth is low and users should be aware of this fact. Second, mag-
netic mineralization is a property which is particularly seen with mineralized rocks and
this measurement plays an important role for the device to eliminate the false signals
produced by these rocks.
ROCKS AND SEARCHING IN ROCKY TERRAINS (GENERAL AND DISCRIMINATION MODES)
Challenging ground conditions arise especially when conductivity and magnetic properties
of the ground is too intense. Operation of the device over such ground is made possible
by selecting the best operating mode and using proper ground balance, gain, iSAT and
threshold settings.
Stones and rocks or cavities inside the ground are as important as the ground itself in regards
to the search and target detection quality.
Soil and rocks have two different properties just like the targets you are searching for. One
of them is the intensity and the other one is the conductivity - magnetic permeability ratio
and these two properties are independent from each other. In this manual, the conductivity
- magnetic permeability ratio will be referred to as ID in short. High magnetic permeability,
low conductivity results in low ID. Soil or rocks can be highly permeable and have low or high
IDs as well. If the conductivity increases relatively to magnetic permeability then the ID will
also increase.
Hot rocks are classified as negative or positive based on their ID being low or high in com-
parison to the ID of the soil they are in. One or both of the types may be present in a field.
The negative and positive effects mentioned here will only be valid if ground balancing
is properly done on the existing ground. Otherwise, soil itself will not act differently from
hot rocks in terms of ID. In ''Tracking'' however, conditions will differ. Therefore, the effects
of rocks in tracking will be discussed separately. Here we are referring to a proper ground
balance without tracking.
Positive rocks act just like metal and produce a metal sound. In the General Search Modes
(GEN and GEN (D)) they produce a “zip zip” sound when the search coil is moved over them.
If the signal is strong enough, the device may produce an ID for these rocks. Negative rocks
in the General Search modes, produce a long “boing” sound when the search coil is moved
over them. The device does not give an ID for these rocks even if the signal is strong.
Positive rocks provide a typical metal sound in discrimination modes. Negative rocks do not
provide a sound in discrimination modes (except for rare cases of false signals).
At higher settings of iSAT, there will be no change in the sounds of positive or negative hot
rocks. As the iSAT value is decreased, the sound of positive hot rocks will remain the same
but the negative hot rocks may give a thinner beep sound instead of the boing sound.
Therefore, you can make a decision by listening to the audio responses produced by the
device in the field. If you receive a metal sound, it means that you either detected a positive
rock or a piece of metal. If you receive a strong signal and a stable ID, you can distinguish
if the detected target is a rock or metal by checking the ID. However, remember that weak
signals may produce different IDs and metals under rocks may produce different metal
signals. Therefore, the most appropriate action is to dig up when a metal signal is received.
If you are operating with discrimination modes and you know the ID of the surrounding
rocks, you can use the Disc. setting to eliminate the rocks. However, this may not be sufficient
to avoid all rock signals. The device may still receive signals from rocks because soil and rocks
together will form a combined effect and generate a different ID than those of rocks.
NOTE:
In static modes, the device will produce an audio response for the positive rocks but
not for the negative ones. The effects of rocks will be reflected on screen as drifts in the right
(positive) or left (negative) direction in the ID scale. In the case of a positive drift, there are 2
ways to check whether the target is a rock or not:
1)
If the ID scale fills up instantly along with the audio and then drops,
2)
If it does not provide any ID at all or a very low ID, then the target is a rock.
TRACKING AND EFFECTS OF ROCKS
When the tracking is active, the device may give an audio response and ID when it passes
over a hot rock because the effect of the rock will be different than the ground's. If you
swing the search coil over the rock, tracking will automatically adjust the setting and the
audio response/ID will either disappear or diminish significantly. Because there is a slight
delay in tracking, you may hear a strong signal at the first one or two swings until the
setting is adjusted. Then the sound will get weaker and disappear. This will not happen with
metal targets because metals will prevent the device from ground balancing. Therefore, in
tracking, if you are getting a constant signal over a target after repeated swings, there is a
high possibility that the target is a metal. Moving from over a rock back to soil, the device
may give signals to the ground for a few swings until the ground balance setting is updated
again. This is normal and should not mislead you.
Tracking is not recommended to eliminate rocks under normal conditions. It is recom-
mended for use in areas with changing soil types.
METALS UNDER ROCKS
IMPACT
increases the possibility of detecting metal targets under mineralized rocks through
the proper adjustment of your settings. The combined effect created by the rock and metal
together is lower than the effect that the metal creates by itself and the displayed ID will be
different than the metal's expected ID. The displayed ID is formed by the combination of rock
and metal together and gets closer to the ID of the rock if the size of the metal is smaller in
relation to the rock. Keep in mind that metals under hot rocks will never appear with their
own metal ID. For instance, a gold piece under a brick may produce an iron tone and ID.
Remember this very simple principle as it will save you lots of time: “If the target you detect
is not a stone, it can be metal”.
The key to detecting targets under mineralized rocks, particularly when positive rocks are in
question, is the knowledge of the maximum ID value produced by the surrounding positive
rocks. If you are performing a search in the General Search modes, monitor the ID produced
by the device. If the ID provided by your device is close to the rock and iron zone, it is quite
possible that you detected a target under the rock. In the case of using Disc. in the GEN
mode, all rocks below the Disc. level will produce a low iron tone and all above will produce
a higher tone.
If you filter off the rocks with a correctly adjusted ID Disc. setting in discrimination modes,
you can hear the signal of the target under the rock if the target signal has a slightly greater
effect than the filtered ID. The important thing here is that if you detect a target and dig out
a rock, you should note the ID you got before digging and use it as the Disc. value the next
time.
For instance; the hot rocks in your search field tend to give IDs around 00-01. In this case, you
should set the Disc. to maximum 02. This way you can eliminate rocks and receive the signals
of metals underneath. If you set the Disc. too high unnecessarily, you will lose metals along
with rocks.
If the hot rocks in your search area tend to give high IDs, then the chances of missing the
signals of small metals underneath will be high as well.
SEARCHING IN SHALLOW WATER AND BEACH
All search coils of the
IMPACT
metal detector are waterproof. This provides convenient
searching in shallow water and on the beach. When searching around water, be careful not
to get the system box wet. This includes the arm cup and control head electronics.
As explained before, salt water and alkali grounds are significantly conductive and cause
effects similar to iron in detectors.
IMPACT
’s COG mode is specially designed for such
conditions. You can perform your search easily using the COG mode without requiring any
special settings.
COG mode is ideal for salty wet beach sand. You can use the other modes while performing
search over dry beach sand.
You should consider the following while performing search over wet beach sand or
water:
1)
When you swing the search coil over the holes you dig in wet beach sand, you can receive
metal signals, this is a normal condition.
2)
The search coil may give false signals when going into and coming out of the water so
please try to keep the coil either in or out of the water.
