Handleiding Nokta Impact (pagina 33 van 40) (Engels)

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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

Page 29

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.

Nokta Impact Handleiding

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