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GP Extreme
User Manual
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Minelab GP Extreme User Manual

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Minelab USA Inc
871 Grier Drive, Suite B1, Las Vegas, Nevada, 89119 United States of America Telephone: +1 (702) 891 8809 Facsimile: +1 (702) 891 8810 Email info@minelabusa.com
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4901-0036-Revision 1.2
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THE MINELAB ‘GP extreme’
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© Minelab Electronics Pty Ltd
This document contains proprietary information which is protected by copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without written permission from Minelab Electronics Pty Ltd, 118 Hayward Avenue, Torrensville, SA 5031, Australia.
WARNING. This document contains Minelab Electronics Pty Ltd rights, technical data or restricted rights data, or both. Patents and trademarks apply.
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TABLE OF CONTENTS
contents
6
DETECTING TECHNIQUES ............................................................................................... 39
Detecting techniques............................................................................................................................... 40
Prospecting techniques ..........................................................................................................................42
Identifying target signals......................................................................................................................... 43
Recovering the target ............................................................................................................................. 45
USER INFORMATION ........................................................................................................ 49
Technical specifications for the Minelab ‘GP extreme’ .......................................................................... 50
Troubleshooting....................................................................................................................................... 51
Service repair form ................................................................................................................................. 52
Warranty .................................................................................................................................................53
Accessories ............................................................................................................................................ 54
Glossary of common terms ................................................................................................................... 55
Detector care and safety ........................................................................................................................ 59
An important message from Minelab ..................................................................................................... 60
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ABOUT THIS MANUAL
This manual is designed to introduce the detector’s features. It gives you step-by-step directions for everything from assembling and adjusting your detector, to basic and advanced detector use.
1. INTRODUCTION
Basic overview of the ‘GP extreme’ and this User
’s Manual.
2. ASSEMBLY
This chapter provides details and instructions on assembling and adjusting the ‘GP extreme’
.
3. BATTERY
The ‘GP extreme’ is powered by a rechargeable battery pack. This chapter provides details on battery installation, use and performance.
4. CONTROLS
This chapter is designed to familiarize you with the various features of the ‘GP extreme’ control panel. A few minutes spent reading this chapter will be a worthwhile preliminary to basic or advanced detecting.
5. DETECTOR OPERATION
However experienced you are at using a metal detector, it is important that you read this.
6. DETECTOR TECHNIQUES
Once you are comfortable with the basic detector use, there are a few techniques you should be aware of.
7. USER INFORMATION
This chapter provides a glossary of terminology, user guides, technical specifications, warranty and repair details and troubleshooting tips.
ABOUT THIS MANUAL
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Assembly
This chapter provides details and instructions on assembling and adjusting the ‘GP extreme’.
THE MINELAB ‘GP extreme’
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INTRODUCTION
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Minelab is always interested in your opinions so if you have any questions or comments regarding the ‘GP extreme’ or any other Minelab product, please feel free to contact us via your local Authorized Minelab dealer, or write to us:
Minelab International Limited Laragh, Bandon Co. Cork IRELAND email: minelab@minelab.ie tel: + 353 (23) 52101
Contact Minelab
Minelab Electronics Pty Ltd PO Box 537 Torrensville Plaza South Australia 5031 AUSTRALIA email: ho@minelab.com.au tel: + 61 (8) 8238 0888
Visit our site on the World Wide Web: http://www.minelab.com for the latest information on Minelab products and services.
Minelab USA 2700 E Patrick Lane, Suite 11 Las Vegas, Nevada 89120 UNITED STATES OF AMERICA email: minelab@minelabusa.com tel: + 1 (702) 891 8809
Minelab USA Inc 871 Grier Drive, Suite B1, Las Vegas, Nevada, 89119 UNITED STATES OF AMERICA email: info@minelabusa.com tel: +1 (702) 891 8809
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UNPACKING YOUR ‘GP Extreme’
A. ‘GP extreme’ 1100 Coil with Skid Plate and
Fibreglass Lower Shaft attached. B. Intermediate Shaft. C.
‘GP extreme’ Control Box with Upper
Shaft, Handle, Arm Rest, Arm Straps and
Neoprene Armrest Cover attached. D. Headphones. E. Battery and Battery Pack. F. Velcro Straps, Knuckle and Bungy Cord.
G. Battery Cable. H. Vehicle Charger. I. Mains Charger. J. Backpack Strap. K. Instruction Manual, Field Guide and Rubbish Bag. L. Hard Carry Case. M.
‘GP extreme’ 1800 coil with skidplate (in separate carton).
The ‘GP extreme’ as shipped
Figure 2.1 Contents of the ‘GP extreme’ pack
P0501-A
easy reference
UNPACKING YOUR ‘GP extreme’
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Inventory
When unpacking your ‘GP extreme’, you will find that a number of the components have been pre-assembled for your convenience. Figure 2.1 (page 6) shows a list of the parts as they are packed. Figure 2.2 (page 7) shows the pre-assembled sections and a list of parts.
Should you need to assemble the ‘GP extreme’ from all the various components, here are detailed assembly instructions.
Assembling and fitting the armrest
Figure 2.3, refer also Figure 2.2
STEP 1 Place the two armrest halves (11) on either side of the upper
shaft (8) and ensure that the bolt holes are aligned.
STEP 2 Slide the two nylon bolts (12) through the bolt holes and
screw the nylon wing nuts (13) onto the bolts by a couple of turns.
STEP 3 Slide the ‘T’ section on top of the control box (10) into the
armrest with the battery plug at the rear. Tighten the nylon wing nuts by hand.
STEP 4 Attach the arm rest straps (14) using the press studs on both
sides of the arm rest.
STEP 5 Push the arm rest straps (14) through the slots in the
neoprene arm rest cover (15) and then push the cover over the arm rest (11).
COMPLETE ASSEMBLY INSTRUCTIONS
COMPLETE ASSE MBLY INSTRUCTIONS
Fig ure 2.3 Armrest assembly
P0518-A
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COMPLETE ASSE MBLY INSTRUCTIONS
Securing and connecting the coil cable
NOTE Always ensure that the control box is turned off
completely before connecting or disconnecting the coil.
STEP 1 Wind the coil cable around the shaft and plug the coil
connector into the coil socket on the control box. Check that the cable is wound firmly around the shaft without strain, leave enough slack at the bottom of the cable near the coil to allow for adjusting the angle of the coil without placing strain on the coil cable.
STEP 2 Fasten the cable into position using the Velcro straps
provided (20).
Fitting and connecting the battery pack
Figure 2.6
STEP 1 Fit the battery (17) into the back pack pouch (18). STEP 2 Connect the headphones (16) and the power cable (19) to
the appropriate sockets in the cap of the battery.
STEP 3 Put on the back pack (18).
If the coil cable is able to move
around, especially near the coil, it
will be
‘seen’ by the detector and
cause random noises which may be
confusing.
HINT
Use only the 6v DC battery supplied
CAUTION
Attaching the lower fibreglass shaft
Figure 2.2
STEP 1 Slide the lower fibreglass shaft (4) into the intermediate shaft (7). STEP 2 Adjust shaft length and coil angle for a comfortable position.
Minelab recommends that the shaft length be set to give a comfortable sweep length of approximately 2 meters. The lower fibreglass shaft can be set into position by locating the spring clip into the holes provided in the intermediate shaft and hand tightening the locking nut at the end of the intermediate shaft.
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BATTERIES
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The Battery
The 6v DC rechargeable battery should provide enough power to operate the detector for 10-12 hrs, when fully charged.
The battery may be recharged at any time during the discharge cycle. It is very important to fully charge the battery before storage. Do not leave a battery fully discharged for longer than one day.
CAUTION Never use a 12v DC battery because this would
damage the detector. This damage is not covered by warranty.
Low Battery Indication
If battery level drops below the desired power to give full function, a series of signal pulses are given at 0.5 second intervals.
Charging the battery
STEP 1 Turn the detector Off before disconnecting the battery. STEP 2 Disconnect the battery cable from the detector and connect
to the appropriate charger.
Battery Chargers
Two types of battery chargers (Mains and 12v Vehicle Charger) are supplied.
BATTERY AND CHARGING
BATTERI ES AND CHARGING
Do not leave the mains charger
on for extended periods because
reduced battery life may result.
Caution
When charging, the battery must
be kept in an upright position.
Important
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easy reference
DETECTOR SOUNDS
DETECTOR SOUNDS
Threshold and Tone
This is the background sound produced by the detector. The level is set using the Threshold control. The tone of the threshold is set using the Tone control.
Target Signal
This is the abrupt change of the tone and volume of the threshold sound when a target is detected.
• The maximum level is set by the Volume control.
• The amount of tone variation is set by the Signal control.
• If the tone falls first and then rises, as the coil is passed over a target, this generally indicates a small target.
• If the tone rises first and then falls, as the coil is passed over a target, this generally indicates a large target.
Ground Noise
These are irregular noises that are difficult, or impossible, to pinpoint when moving the coil over the ground. Ground noise is caused by the changing chemistry or 'mineralisation' of the ground. When the Balance switch is set to Tracking these effects are greatly reduced.
Tune Indication
An initial beep sounds then, while the detector is testing the range of frequencies for the most stable, the threshold may become more quiet or chattery. Once selection is complete three sharp
‘beeps’ are given.
Low Battery Indication
If the battery level drops below the desired power to give full function, a series of signal pulses are given at 0.5 second intervals.
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CONTROLS
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CONTROL FUNCTIONS
Boost (Shallow/N/Deep)
Figure 4.3
Enhances the signals produced by different types of targets.
• Shallow enables target signals, from small objects close to the surface of the ground to be amplified. This allows for easier detection. This setting is best suited for 'quiet' ground.
• N (Normal) may be used for normal detecting conditions. This setting responds to all signals without boosting.
• Deep may be used when searching for large targets at greater depth in 'noisy' ground. Random soil signals are smoothed, making small changes in the audio signal from large deep targets easier to hear. This may mask some signals from very small targets near the surface.
Threshold
Figure 4.4
Adjusts the background audio signal or 'threshold' level. The Threshold control should be set just above the point where
the threshold is just audible and stable. This level should not be at a level where prolonged use may be
irritating. Ideally it should be a smooth, gentle hum.
NOTE Small targets or large deep targets may not produce a
distinct target signal, but may cause only a small variation in the threshold level. If the threshold level is set too high or too low, these very small variations may be missed.
In Figures 4.5 - 4.7, the dotted line represents the level at which the audio output becomes audible; signals cannot be heard if they are below the dotted line.
If the threshold level is set too high then small variations in audio signalmight not be discernible above the threshold level (Figure 4.5). An example of this would be to hear a whisper within a crowded noisy room.
Figure 4.5 Threshold control too low
P0509- A
Figure 4.6 Threshold control too high
P0509- B
Figure 4.3 Boost switch
Boos t
P0519- A
Figure 4.4 Threshold control
Audio
P0520- A
e
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Tone
Figure 4.15
Adjusts the tone of the threshold. The user may set this to the preferred tone, e.g. the tone at which the operator
’s hearing is
most sensitive. At minimum position, threshold is set at a low tone. Turning
clockwise increases the tone to higher pitch.
Signal Pitch
Figure 4.12
Adjusts the pitch response of the target signal. In Figures 4.13 and 4.14 the curving line represents the high/low
pitch response to a target. The dotted line represents the threshold tone.
• At minimum position the high/low pitch variance to a target is reduced.
• At maximum position the high/low pitch variance to a target is increased.
CONTROL FUNCTIONS
Figure 4.12 Signal control
Audio
Figure 4.13 Reduced pitch variance
Figure 4.14 Increased pitch variance
P0522- A
P0510- A
P0510- B
Audio
Figure 4.15 Tone control
P0523- A
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CONTROL FUNCTIONS
Iron Discriminate (All Metal/Disc)
Figure 4.18
Selects between discrimination or to turn off the discrimination altogether (All Metal).
In All Metals, the detector will give varying volume and pitch signals but this information does not indicate the type of metal in the object.
In Disc, a strong response from a ferrous (iron) object will cause the threshold to be 'blanked' or silenced.
NOTE If the target response is too weak for accurate
discrimination, the detector will give a normal target signal.
Level Adjust
Figure 4.19
Level adjust gives the user the ability to select the sensitivity and likelihood of a target being ferrous or non-ferrous.
It also affects how the detector recognises mineral effects in the ground, as opposed to metal targets, when 'ground balancing'.
NOTE It is important that you read pages 37 and 38 in
Chapter 5 for more information.
Soil (Normal/Sensitive/Salt)
Figure 4.20
Optimises the detector for different soil conditions and targets by changing the signal processing.
• N ( Normal ) may be used in all areas, including areas with highly mineralised soil. This position has very good sensitivity to a wide range of nugget sizes and is the most versatile of the three positions.
Iron D iscrim inate
Figure 4.18 All Metal/Disc switch
P0525- A
Iron D iscrim inate
Figure 4.19 Level Adjust control
P0526- A
Soil
Figure 4.20 Soil (Normal/Sensitive/Salt) switch
P0527- A
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Cancel will again be to one side of centre and signals may
be complex if target is close to the coil. This setting will limit sensitivity to deep targets.
NOTE Coils not specifically designed for the
‘GP extreme’ may behave erratically or be ineffective in either E (Enhance) or Cancel modes.
Balance (Fixed/Tracking)
Figure 4.21
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 that is described on page 33.
To obtain the best performance from your detector, it is important to know how different ground conditions affect the detecting process. See
“Ground Balancing” on page 33 for more detailed information.
Balan ce
Figure 4.22 Balance (Fixed/Tracking) switch
P0529- A
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DETAILED OPERATING INSTRUCTIONS
Turn the ‘GP extreme’ On
• Hold the coil away from the ground and metal objects and switch Power to On.
NOTE When the ‘GP extreme’ is turned Off, important
information (e.g. tuning frequency and ground balance) is saved in internal memory.
If detection recommences in the same location, the user should not have to re-tune or re-ground balance the detector.
Set the Volume Control
Volume should be set so that target signals are clear and easy to hear but loud signals are not uncomfortable to your hearing.
Set Volume by testing volume levels by passing coil across a large target and setting volume at comfortable level. Now test very small target at this level.
Set the Threshold control
• Adjust the Threshold control until the threshold is just audible through the headphones.
NOTE Small surface objects, as well as large deep objects,
will produce very small changes in the threshold. It is important to set the Threshold control correctly to ensure that these targets are heard. Experiment with known targets to assist in setting all controls to suit your hearing.
DETAILED OPERATING INSTRUCTIONS
HINT
Take time to read this manual
thoroughly to obtain the best performance from your new
‘GP extreme’ detector.
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QUICK START INSTRU CTIONS (EASY REFERENCE)
easy reference
STEP 1 Turn Power switch On. STEP 2 Set Boost to N (Normal) for general detecting. STEP 3 Set Volume to maximum, and Signal to midway. STEP 4 Adjust the Threshold control so that a faint sound is heard
through the headphones.
STEP 5 Adjust Tone for threshold level that suits your hearing. STEP 6 To tune the detector, hold at waist height with the shaft
horizontal. Keep the coil vertical.
STEP 7 Slowly move coil around your body through a half-circle
until the noise from interference is loudest.
STEP 8 Hold this position, keep the coil motionless and push the
Tune switch once to start the tuning function.
STEP 9 Tuning takes approximately 60 seconds. A series of three
beeps will indicate that the optimum frequency has been selected.
STEP 10 For Discrimination, change the Iron Discriminate
switch to Disc and set Level Adjust to the middle of its range.
STEP 11 Set Soil switch to N (normal) STEP 12 Set Rx switch to Normal STEP 13 Set the Ground Balance by moving the coil up and down.
While coil is in motion, change Balance switch from Fixed to Tracking
.
STEP 14 The detector is now ready for operation.
QUICK START INSTRUCTIONS
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DETAILED OPERATING INSTRUCTIONS
Set the Tone control
• Adjust the Tone control until the threshold is at a comfortable tone for your hearing. Interpretation of the target signals involves understanding the difference between the rising and falling tone and volume of the threshold in response to different targets.
HINT Setting Tone to a high pitch may be more fatiguing, but is
more suitable for identifying the faintest target signals.
Set the Signal control
The human hearing is sensitive to changes in tone, so the operator is more likely to hear a target signal when both the volume and the tone change rather than volume alone.
The Signal control gives the operator, the ability to choose between a target signal that has a large variance of tone or one which has less variation.
High variance can give the operator more signal definition to interpret, however in highly mineralised ground this high variance of signal may cause confusion and a lower setting preferred.
Soil switch
Use this switch to optimise the detector's ability to detect in different ground conditions (see page 24 for full description).
Rx switch
Selection of different positions of this switch, changes the electromagnetic field of the coil thus giving better performance in certain environments (see page 25 for more information).
Normal has the coil operate in a conventional Double D search pattern with all the same advantages and disadvantages.
IMPORTANT
You will need to
re-ground balance every time you
select a new position for either the
‘Soil’ or ‘RX’ switches.
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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
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GROUND BALANCING
Ground Balancing Procedure
Figure 5.2
• Move the coil up and down between 20mm and 100mm above the ground and, while moving the coil, change Balance from Fixed to Tracking
.
• The fast ground balance takes only 5 sec. after switching to Tracking. Therefore, it is important to be moving the coil as the switch is changed.
• Keep moving the coil until all ground noise has stopped. A persistent signal may indicate a target in the ground.
• If this occurs, then move the coil to a new location and repeat the procedure.
• When there is no longer a change in the threshold, while the coil is being raised and lowered, the detector is 'ground balanced'.
• When the detector has been ground balanced, the user may select either Fixed or Tracking for detecting.
If the ground is mineralised or variable, use Tracking. If the ground is very 'mild', use Fixed and switch back to Tracking
temporarily if the threshold becomes noisy. Do not test a target by switching to Tracking when the coil is above it.
HINT It may useful to repeat the ground balance procedure if
ground conditions change rapidly.
Figure 5.2 Setting the ground balance
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IRON DISCR IMINATION
Iron Discriminate
Figures 5.4, 5.5
Iron discrimination with the ‘GP extreme’ is the silencing or ‘blanking’ of the threshold which occurs when the detector determines a target is comprised of ferrous metal.
There is no discrimination when Iron Discrimination is set to All Metal. Targets will cause the tone and volume of the threshold to vary. These variations convey no consistent information about the type of metal detected.
Iron discrimination operates when Iron Discriminate is set to Disc
. Objects must produce sufficiently strong target responses for the detector to successfully discriminate. Fortunately, most iron rubbish is located near the surface and should produce the required strong signal response.
NOTE When Disc is used, small or deeper targets, whether
ferrous or non-ferrous, will produce a normal target signal.
If a target response is too weak for the detector to discriminate, it will internally change to the all metal mode. As soon as the target response becomes strong enough, the detector will resume discrimination.
Pinpointing is best performed using All Metal
.
HINT When a target has been located using Disc, the coil should
be rapidly passed back and forth over the target centre several times. Remember to set Balance to Fixed for this.
The coil should always be passed smoothly over the surface of the ground, while maintaining the coil height above the ground. This is especially important when attempting to discriminate a target.
NOTE Discrimination will give the best results when used in
combination with the specially designed
‘GP extreme’ coils.
When detecting a piece of iron, a normal target signal should be heard until the detector determines that the object is ferrous.
At this point, the signal will 'blank'. The strength of the target response required for discrimination to
occur may be altered by using Level Adjust
.
Figure 5.4 A normal signal on a non-ferrous target.
P00514-A
Figure 5.5 Discrimination target signal on a ferrous target.
P00514-B
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Level Adjust Control
Level Adjust gives the user the ability to select the sensitivity and
likelihood of a target being discriminated as ferrous when used in the Disc mode.
This may also affect how the detector responds to ground mineralisation compared to metal targets when used in Disc. Mode.
There is usually some overlap between signals from useful targets and some types of iron rubbish. The user may set Level Adjust to select the amount of discrimination between two extremes:
• (Fully anti-clockwise). All targets detected, but some iron will give a normal signal (as per Figure 5.4).
• (Fully clockwise) Little iron detected, but some small non­ferrous targets potentially mistaken as ferrous.
Turning the control anti-clockwise increases the strength of a signal required for iron discrimination to be activated.
The Level Adjust also affects the Tracking mode. When set fully clockwise, it is unlikely the detector will 'balance out
'
genuine targets, but some ground noise may still give false signals. When set fully anti-clockwise, the detector will 'balance out' ground
noise effectively, but some faint, weak target signals may be missed after repeated sweeps of the coil.
HINT It is usually best to dig out all targets and only use the
discrimination function in areas where a large amount of rubbish makes the digging of everything impractical.
NOTE Discrimination functions will only work with strong,
positive target responses. Weak responses will give normal 'all metal' type signals.
IRON DISCR IMINATION
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IRON DISCR IMINATION
easy reference
DISCRIMINATION CONTROL USING LEVEL ADJUST
MIN (FULLY ANTI-CLOCKWISE)
Most iron objects are discriminated, but a few small iron objects will be accepted as non-ferrous.
Detect more rubbish, but less likely to cancel a gold nugget.
Suggested for areas with large amounts of ferrous rubbish.
Only very strong target responses will trigger discrimination action.
Tracking is more likely to balance out weak target responses.
A medium to strong target response should pause the tracking mode but weak responses may be mistaken for ground mineralisation.
MAX (FULLY CLOCKWISE)
Almost all iron objects are discriminated, but a few small non-ferrous items will also be ignored.
Detect less rubbish, but may mistake a nugget for ferrous rubbish
Suggested for areas with small amounts of ferrous rubbish
Both strong and medium target responses will trigger discrimination action
Tracking is less likely to balance out weak target responses.
Aweak target response should pause the tracking mode.
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Some user tips:
• The battery should be worn in the backpack supplied. This places the battery at the furthest practical distance from the coil.
• Ensure that you do not set the shaft length too short.
• If the coil is too close to your body it might detect your pick, the battery or any other metal which you are carrying. If false signals are occurring as you sweep the coil, check that they are not produced by any metal that you are carrying.
• Move the coil closer, and then further away from your body, in order to check if the signals are coming from items such as your pick or battery. If they are, you must increase the distance between the coil and these items.
Motion detection
The ‘GP extreme’ is a 'motion' detector. Therefore the detector must be moving over a target to detect it.
Parallel Sweeping Procedure
Figure 6.1
• The coil should be swept over the ground in a side-to-side sweeping motion.
• While sweeping the coil, it is important to keep it parallel to, and at the same height from, the ground at all times. Lightly skidding the coil across the ground can sometimes help in this, depending on mineralisation.
• Do not raise the coil at the ends of each sweep as this will reduce the detection depth and may cause false signals.
DETECTING TECHNIQUES
DETECTING TECHNIQUES
Figure 6.1 Parallel Sweeping
Check your footwear
Note: When detecting, do not wear
steel cap boots or shoes with
metal eyelets!
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DETECTING TECHNIQUES
Covering the search area
Figure 6.2 and Figure 6.3
• As the user moves forward slowly, the search pattern should resemble a snaking path.
• To ensure that the ground is thoroughly searched, approach the area from 3 different directions.
Overlap each sweep
• Each sweep of the coil should overlap the area covered by the previous sweep to ensure a full coverage of the area being searched.
• Be aware of the search pattern of the coil being used and overlap sweeps to take this pattern into account.
• See also Pinpointing Technique, pages 43 and 44.
C
A
B
Figure 6.2 Search path
Figure 6.3 Search area from 3 directions
P0530-A
P0531-A
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PROSPECTING TECHNIQUES
The ‘GP extreme’ has superior ground balancing and it is possible to find quite large objects near the surface in well-worked areas where other detectors have been unable to cope with the high degree of mineralisation and / or salt. Therefore the user should dig all target signals, even in previously detected areas.
Very sudden or large changes in the mineralisation of an area may produce a signal from the detector.
In the Victorian goldfields, a response may be received from a concentration of orange/reddish dyke material or clay. In the loamy conditions of Western Australia, a pocket of dark orange/reddish colouration may produce a sudden signal change.
If detecting areas of extremely variable mineralisation, detecting with the contours rather than across the changes will often stabilise the effect.
In some ground (particularly heavily mineralised areas) the operator may need to sweep the coil 1 or 2 cm above the ground. This should give a more stable threshold and less ground noise.
Charcoal may sometimes produce signals, similar to a metallic object, when close to the surface. Charcoal is usually created by farmers burning off tree stumps or by bushfires.
When the charcoal under the surface is disturbed, the signal will vanish.
If in doubt, scrape away some soil above the suspect signal; if the signal gets stronger, it is likely to be a target. Dig it!
PROSPECTING TECHNIQUES
Keep the coil as close to the
ground as possible.
Listen very carefully - this is
more important than looking.
SLOW DOWN! Do not rush, take
your time.
For Maximum Gold Recovery
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IDENTIFYING TARGET SIGNALS
Pinpointing
To find an object, and reduce the size of the hole required to remove it from the ground, it is necessary to pinpoint the exact location of the object.
If a target is heard, first confirm it by setting an accurate ground balance and then pinpointing. To ground balance, the coil should be passed around the area of the target, making sure that the target is not detected (keep the coil away from where the target is)
While the coil is moving around the area of the target, change Balance to Fixed. This will give a very accurate 'ground balance
'
on this area. One of the pinpointing techniques may then be used. When a target is detected, sweep the general area with the coil,
taking note of where the strongest signal is received. By shortening the length of the sweep it should be possible to draw
an imaginary line in the ground where the strongest signal is located. Line up the target at 90
° from the initial direction and repeat the process. The object is located where the two imaginary lines cross (see Figure 6.4).
Figure 6.4 Pinpointing technique
NOTE Pinpointing will not locate a target in the centre of
the coil if operating with the RX switch set to Enhance or Cancel.
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RECOVERING THE TARGET
STEP 9 Keep halving the pile which has the target. STEP 10 If it is still difficult to find the target, place the detector on the
ground with the coil horizontal.
STEP 11 Take a handful of the diggings and pass over the coil.
• Your hands and wrists must be free of any metallic jewellery and watches.
STEP 12 If there is no signal, place the handful carefully in a new pile
and repeat with another handful.
NOTE Always refill any holes before leaving, and scatter
leaves, etc. to restore the area to its original condition. Any rubbish you recover should be taken away with you and disposed of properly.
Recovering Deep Targets
The ‘GP extreme’ has depth capabilities that will surprise both new and experienced prospectors. If the target appears to be buried deeply, it should help to use the following technique:
STEP 1 Use the cross sweeping method to locate the target accurately. STEP 2 Dig a hole large enough to insert the coil, approx. 100mm deep. STEP 3 Keep testing the target location as you dig deeper. STEP 4 Take care that the target is not in the wall of the hole. You
may dig past it. Try pinpointing again to check your hole is in the correct position.
REMEMBER Removing rubbish and refilling holes will help metal
detector users maintain a good reputation. This should lead to more areas being readily accessible for prospecting.
When the object has been
recovered, it may be worthwhile
sweeping the hole again to
ensure that there are no other
targets.
If you find an object in a
particular location, search the
surrounding area very carefully. It
is likely that there are more
objects nearby.
If you hear a target signal, keep
searching until you find the
object; it is there and may be
valuable
HINT
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Salty Environments
The ‘GP extreme’ will find objects at greater depth in salty environments. However, the interfering signals caused by highly concentrated salt may not be able to be completely 'balanced out' if using automatic ground balance alone.
HINT Change Soil switch to Salt setting for salty environments.
To use the salt setting, you will have to use the specially designed ‘GP extreme’ range of coils.
RECOVERING THE TARGET
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TECHNICAL SPECIFICATIONS
Length Maximum 1300mm
Minimum 1100mm
Weight Complete with 11
” coil 2400g
(exluding battery) Configuration Shaftmount Transmit Freq. Bi-level Pulse Induction Technology Dual Voltage Technology (DVT) Ground Rejection Automatic ground balance Search Mode Motion detector Controls Power (On/Off) 2 pos. switch
Boost (Shallow/N/Deep) 3 pos. switch
Threshold 1 turn control
Volume 1 turn control
Signal 1 turn control
Tone 1 turn control
Tune push switch
Level Adjust 1 turn control
Iron Discriminate (All Metal/Disc) 2 pos. switch
Soil (Sensitive/N/Salt) 3 pos. switch
Rx (Normal/E/Cancel) 3 pos. switch
Balance (Fixed/Tracking) 2 pos. switch Audio Output 6.35mm (1/4") headphone socket
Audiotelex headphones 600 ohm Coil (standard) Extreme 1100 (Double D)
Extreme 1800 (Double D) Battery 6VDC 10A/hr sealed lead acid 10-12hrs
Patent s Apply
Note: In the interest of product improvement, Minelab reserves the right to make changes without notice.
TECHNICAL SPECIFICATIONS
The ‘GP extreme’
Table 7.1 Technical specifications
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Today’s Date ___________________________________________________________________________
______________________________________________________________________________________ Detector Model ________________________ Serial No. ________________________________________ Purchased From_________________________________________________________________________ Purchase Date __________________________________________________________________________ Faulty Part(s): __________________________________________________________________________
______________________________________________________________________________________ Description of Fault: ______________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
Owner
’s Name __________________________________________________________________________
Address________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________ Phone Day ( )______________________ Home ( ) _______________________________________
Fax ( ) ____________________________ Email ____________________________________________
SERVICE REPAIR FORM
SERVICE REPAIR FORM
If necessary, use the space provided overleaf to continue your description of the fault.
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ACCESSORIES
ACCES S O R I E S
Search coils
The ‘GP extreme’ is supplied with the ‘GP extreme’ 1100 and ‘GP extreme’ 1800 coils. These coils have been specially designed to take advantage of the new technology and features of this detector. In addition to this there are also a number of other size coils will become available in the near future.
These range from smaller coils which give greater sensitivity to small targets and are lighter and manouverable in heavy vegetation, up to larger coils which give greater depth. See your Minelab retailer for the full range.
In some circumstances, other Double D and Monoloop coils will work on the
‘GP extreme’, however there are limitations which will mean that a number of the new benefits of the DVT will not work properly. In some cases the use of coils not designed for the ‘GP extreme’ will cause the detector to be unstable and noisy.
Batteries
Spare 10A/hr batteries can be an advantage, especially if travelling into the outback.
A smaller light-weight battery is also available from Minelab. This is rated at 4.5A/hr and gives approx. 3 - 4 hours running time per charge. The weight of this battery is 968g.
Corporate clothing
Minelab also has a range of good quality clothing, e.g. caps, shirts and jackets available. Ask your local dealer for details.
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Halo Effect After a metal object has remained undisturbed in the soil for a
considerable amount of time, a diffusion occurs around the object. This has the effect of the object appearing to the detector to be a larger size.
Hot Rocks A hot rock is an individual rock which has a particularly high degree
of mineralisation as compared to the average ground around it. Due to this high difference, the detector does not have the opportunity to ground balance on the individual rock so therefore gives a false signal.
Interference Electricity or radio waves in the area being detected can cause
instability or chattering of the detectors threshold. The types of interference commonly occur due to power lines,
underground cables, radar, other detectors or climatic conditions like thunderstorms.
Mineralised Ground Most ground contains certain minerals which can cause false signals
to be given by a detector. Heavily mineralised ground requires different ground processing than does neutral or lightly mineralised ground (see Ground Balance).
Ground containing heavy salt concentrations require entirely different processing again (see salt).
Monoloop Coils Monoloop coils are the style of coil where the multiple strands of
wire are wound in a single loop around the circumference of the coil. The field of search of Monoloop coils tend to be cone shaped.
Non - Ferrous Metals Metals not containing significant levels of iron. Non-ferrous metals
are non-magnetic such as Gold, Silver, Copper, Brass, Lead or Aluminium.
Pinpoint The method of locating the precise location of a target prior to
digging. Pinpointing uses the design of the search coil windings to determine the exact position of the detected target.
RX RX refers to the response or electromagnetic field which is received
back by the coil and is used by the control box circuitry to detect a metal item in the ground.
GLOSSARY OF COMMON TERMS
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Salt The presence of high salt content in the ground being searched will
have a similar but different effect on the metal detector ground balance as does mineralisation.
Salt content causes a negative (-) response rather than the positive (+) response of laterite soils. The detector needs to therefore use different filtering techniques to overcome this effect.
Search Coil The search coil is the circular plate which is swept across the ground
surface during detecting. It transmits electromagnetic signals into the ground and receives the response.
Search Pattern The search pattern is the area of ground underneath the coil which
is being scanned. Depending on the style of coil (Double D or Monoloop) and the RX mode being operated in (Normal / Enhance / Cancel) different coils will have a different shaped area being covered by each sweep.
Threshold The continuous audible level of sound emitted by the detector is
referred to as the Threshold. This threshold hum is the background sound made as the detector operates. Threshold can be set anywhere between silent and loud, but a soft, audible level is normally suggested.
Target Response The electro-magnetic effect generated by the metal target under the
influence of the TX field.
Target Signal The audio signal (or change in threshold) caused by the presence of
a metal target as the coil passes across it.
Tracking The function of Automatic Ground Balance where the
‘GP extreme’ makes continuous adjustments to the ground balance to compensate for changes in the mineralisation of the ground.
TX TX refers to the transmit signals or electromagnetic pulses, sent into
the ground by the coil.
GLOSSARY OF COMMON TERMS
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THIS DEVICE COMPLIES WITH PART 15 OF THE FCC RULES
Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
For Consumers within the European Union: Do not dispose of this equipment in general household waste.
The crossed out wheeled bin indicated on this equipment is an indicator that this unit should not be disposed of in general household waste, but recycled in compliance with local government regulations or environmental requirements.
Please dispose of this equipment via a recycling service or centre, or by returning the unit to the respective Minelab or Halcro outlet as appropriate for your unit. This will enable the equipment to be disposed of in an environmentally safe manner.
Disposal of unwanted electronic equipment in landfilled waste may contribute to adverse long term environmental effect due to the leaching of contaminating and toxic substances contained within some electronic equipment.
Working for a Cleaner, Greener Future
Disclaimer:
The Minelab metal detector discussed in this operating manual has been expressly designed and manufactured as a quality hobbyist metal detector and is recommended for use in coin, treasure and general metal detection in non-hazardous environments. This metal detector has not been designed for use as a mine detector or as a live munitions detection tool.
Please note:
Since there may be a variety of options available for this detector, equipment may vary according to the Model or items ordered with your detector. Certain descriptions and illustrations may also differ (in this manual) from the exact Model that you purchased. In addition, Minelab reserves the right to respond to ongoing technical progress by introducing changes in design, equipment and technical features at any time.
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AN IMPORTANT MESSAGE FROM MINELAB
We ask YOU, as a responsible detector operator, to take all due care
regarding the environment.
Minelab cannot stress enough the importance of being responsible
when recovering targets.
BACKFILL EVERY HOLE YOU DIG.
If care and consideration is taken, during and after the removal of
targets, especially with respect to the back filling of holes, this should ensure the continued access to areas for prospecting and
treasure hunting. This will also ensure that the pristine condition of our
beautiful bushland, forests and dry land areas is maintained with a
minimum of damage.
Minelab is working with you towards preserving our natural
environment so that the benefits of gold prospecting and treasure
hunting can continue to be enjoyed in the years to come.
Every prospector and treasure hunter around the world and the
staff of Minelab thank you for your continued efforts towards
protecting the environment.
IMPORTANT MESSAGE FROM MINELAB
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