Minelab GP 3500 Manuel de service télécharger pdf (Page 20)

THE MINELAB ‘GP extreme’

OPERATION

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Sometimes it may not be possible to remove the effects of

interference completely by using the Tune control alone.

Once the detector has been tuned for a particular location, it should

not require readjustment unless conditions change or new

interference is introduced, e.g. other detectors being used in the

same area. If the interference persists after tuning, consider using

the Rx switch set to Cancel position.

Boost (Shallow/N/Deep)

Boost selects the type of processing and filtering applied to the

detector signals.

• N (Normal) may be used for general detecting conditions. This

does not boost any signals.

• Shallow boosts signals from small targets close to the surface.

This makes faint target signals easier to hear. This setting may

also boost any ground noise, therefore Shallow is well suited

for 'quiet' ground conditions.

• Deep may be used when searching for large targets at depth.

This smooths the threshold and target signals from small targets,

making small changes in threshold easier to hear.

Selection of the more suitable position should be after considering

both target size/depth and ground conditions.

NOTE When Boost is changed, Threshold may also need to

be adjusted.

External amplifiers may be used in addition to the Boost switch,

provided that they have loudness limiters built in. This prevents loud

signals becoming unpleasant or dangerous to the user's hearing.

DETAILED OPERATING INSTRUCTIONS

THE MINELAB ‘GP extreme’

OPERATION

GROUND BALANCING

The ground contains not only sand, but also many different chemicals,

minerals and salts. These extra materials are referred to as ground

mineralisation.

This ground mineralisation may often produce a sound from the detector,

known as 'ground noise'.

The

‘GP extreme’ has the ability to cancel out the effects of ground

mineralisation. This minimises ground noise and retains maximum

sensitivity to metal targets. Cancelling the effects of ground mineralisation

is referred to as 'ground balancing'. This ensures that target signals from

objects, such as gold, are not confused with interfering ground noise.

The

‘GP extreme’ has automatic ground balancing. This continually

adjusts to minimise the effects of ground mineralisation when Balance is

set to Tracking

The ‘GP extreme’ may be operated with fixed ground balance or

automatic ground balance.

• When Balance is set to Fixed, the ground balance remains at

the current level.

• When Balance is changed from Fixed to Tracking, the detector

begins to automatically ground balance through a two stage process.

The first stage is a very rapid adjustment to the ground

mineralisation. This lasts for 5 sec. so coil movement should be at the

same time as Balance is changed from Fixed to Tracking

The second stage continues to adjust to the ground mineralisation,

but at a greatly reduced speed.

This adjustment continues all the time that Balance is set to Tracking

While in Tracking mode, the detector usually stops ground balancing

when a target signal is detected. However, a weak target response

may not be recognised as a target if the coil is repeatedly passed

over an object, it may be 'balanced out'. For this reason Balance

should be changed to Fixed when pinpointing a target.

HINTS

• Use ‘Tracking’ in areas with

high ground noise for best results.

‘Balance’ is changed to ‘Fixed’,

the detector will no longer adjust

to changes in ground

mineralisation, but will stay fixed at

the level previously calculated

while in

‘Tracking’ mode.

• Change from ‘Tracking’ to ‘Fixed’

when pinpointing a potential

target.

NOTE

The Level Adjust control also

effects the Tracking mode by

altering the detectors perception of

what is ground noise and what is a

weak target (see pages 37 and 38).

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Minelab GP 3500 Manuel de service Page 20

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