Minelab GPX5000 Instruction Manual download pdf (Page 38)

GPX 5000 Range

GPX 4800 Range

Factory Preset

Off (All Metal), 1–10

Off (All Metal)

Iron Reject

The GPX Series are capable of rejecting many ferrous (iron)

targets while still detecting non-ferrous targets.

While detecting in littered sites, much of the shallow iron

rubbish may be ignored with a high probability that valuable

targets will not be missed.

When Iron Reject is turned off no iron targets will be rejected.

Therefore, all types of metals will produce a target response.

This is known as ‘All Metal’ and is the preferred setting for

most situations.

In All Metal the detector will give varying volume and pitch

signals. This information does not indicate the type of metal in

the object.

When a target has been located; select an appropriate Iron

Reject setting; switch Ground Balance to Fixed, and sweep

over the target. The coil should be passed back and forth

over the target centre several times. Keep the sweep across

the target at an even height and as close to the ground

as possible.

Note: When a target has been

located the coil should be

passed back and forth over

the target centre several times.

Remember to set Ground

Balance to Fixed for this and

keep the sweep across the

target at an even height and as

close to the ground as possible.

Discrimination is dependent on target signals being strong

enough for the GPX Series to determine if the target is ferrous

or non-ferrous. If the signal is weak the detector will give a

non-ferrous response until the signal becomes stronger, i.e.

due to a hole being dug and the coil getting closer to the

target. The Iron Reject function is designed this way to allow

maximum accuracy, while limiting the chances of rejecting a

desirable target.

In some areas, such as mining camps, old building sites

or a farmers’ field, you may choose less cautious levels

of discrimination. This may be because the soil is of low

mineralisation or the targets are large non-ferrous relics

that will not resemble ferrous targets. You may also use less

caution in a goldfield that has high levels of rubbish that

would not be otherwise detectable. Iron Reject allows you

to increase the amount of discrimination while knowingly

accepting more risk.

When Iron Reject is activated the detector rejects ferrous

objects by blanking the normal target signal. You will notice

the Threshold tone goes silent as the coil passes across the

ferrous target.

Tip: To improve

discrimination accuracy

you should always test the

target from at least two

directions (90˚ from each

other) so that the detector

‘sees’ the target from

different profiles.

Caution: Do not attempt

to discriminate by

raising and lowering

the coil on a deep or

partially dug target. An

accurate discrimination

requires an even side-

to-side coil motion. It is

recommended to dig all

targets that do not give an

obvious rejection.

Target signals when detecting in All Metal.

Target signals using Iron Reject. Ferrous target blanked.

Ferrous Target

Audio Signal

Blanking Signal

Non-Ferrous Target

Threshold

Ferrous Target

Non-Ferrous Target

Target signals when detecting in All Metal.

Target signals using Iron Reject. Ferrous target blanked.

Ferrous Target

Audio Signal

Blanking Signal

Non-Ferrous Target

Threshold

Ferrous Target

Non-Ferrous Target

Tip: Pinpointing a target

prior to recovery is best

achieved with Iron

Reject Off.

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Minelab GPX5000 Instruction Manual Page 38

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