Fisher M Scope Gemini 3 Users Manual
GEMINI-3 to the manual 2a404b8d-93fe-4387-aecc-eb5f8e40efe2
2015-02-02
: Fisher Fisher-M-Scope-Gemini-3-Users-Manual-427662 fisher-m-scope-gemini-3-users-manual-427662 fisher pdf
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FISHER RESEARCH LABORATORY
200 West Willmott Road
Los Banos, California 93635
Tel 209.826.3292 Fax 209.826.0416
www.sherlab.com email:info@sherlab.com
QUALITY
Fisher detectors are renowned for their quality.
Each detector is hand crafted in the USA with pride.
PERFORMANCE
Treasure Hunters worldwide rely on Fisher.
Our detectors are durable, dependable, and search deeper..
REPUTATION
Fisher produced the rst patented metal detector in 1931. For
over 70 years, the Fisher logo has been a mark of excellence.
5 - YEAR LIMITED WARRANTY
Fisher believes in the products they produce and backs this be-
lief with a 5 year limited warranty. Warranty may vary outside of
the United States. See your dealer for details.
SERVICE
Fisher is committed to providing their valued customers, with
superior service. Each and every instrument is rigidly tested and
carefully inspected during assembly and before shipment.
Should you have any questions or problems, contact:
FRL#870352-K
Gemini-3
Operating Manual
Deep Search, Two Box Metal and Mineral Detector
FISHER RESEARCH LABORATORY
Gemini-3manual-.ind2 1 6/13/06 2:52:51 PM
CONTENTS
About Your Gemini-3 ...............................................................pg. 3
Basic Theory of Operation .......................................................pg. 4
Depth .........................................................................................pg. 5
Transmitter .................................................................................pg. 6
Receiver ....................................................................................pg. 7
Searching...............................................................................pg. 8
Narrow Scan Inductive Search ...............................................pg. 8
Set Up -Narrow Scan Inductive Search ..............................pg. 8
Tuning -Narrow Scan Inductive Search ..............................pg. 9
Operation -Narrow Scan Inductive Search ........................pg. 10
Wide Scan Inductive Search ...................................................pg. 12
Set Up -Wide Scan Inductive Search ..................................pg. 12
Tuning -Wide Scan Inductive Search ..................................pg. 12
Operation -Wide Scan Inductive Search ...........................pg. 13
Tracing .......................................................................................pg. 14
Inductive Tracing ..................................................................pg. 14
Set Up -Inductive Trace ........................................................pg. 14
Tuning -Inductive Trace ........................................................pg. 14
Operation -Inductive Trace .................................................pg. 15
Conductive Trace .....................................................................pg. 15
Set Up -Conductive Trace ....................................................pg. 15
Tuning -Conductive Trace ...................................................pg. 16
Operation -Conductive Trace .............................................pg. 16
Prospecting Tips ........................................................................pg. 17
Mapping ................................................................................pg. 17
Locating Placer Deposits ......................................................pg. 17
Sources of Error......................................................................pg. 18
Battery Replacement ...............................................................pg. 19
Treasure Hunters’ Code Of Ethics ............................................pg. 20
Where To Use Your Metal Detector In The U.S. ......................pg. 21
Specications ...........................................................................pg. 22
23
Notes
1. Subject to improvement or modication without notice.
2. Approximate.
3. Voltage Controlled Oscillator. Volume and pitch
both increase as target is approached for easier, more
accurate pinpointing.
4. With optional ground plate assembly.
5. Optional stereo/mono headphones.
6. Use of headphones will signicantly increase battery life.
Fisher Research Laboratory does not warrant suitability to
specic use. Fisher Research Laboratory shall in no event be
liable for any direct, incidental, consequential or indirect
damages.
SPECIFICATIONS
Gemini-3manual-.ind2 2 6/13/06 2:52:51 PM
3
ABOUT YOUR DETECTOR
Two-box metal detectors have long been used by
prospectors, geologists, treasure hunters and public utility
companies to locate large, deep objects, ore vein, pipes
and cables. Fisher Research Laboratory is the recognized
leader in the eld, in fact, they were granted the rst two-box
metal detector patent over 60 years ago.
You might think it would be difcult to improve on a product
that has been in a constant state of development for so many
years. But the fact is, the GEMINI-3 is probably the biggest
leap forward in two-box design since it replaced vacuum
tubes with transistors back in the 1950s.
The new GEMINI-3 goes 10 to 20 percent deeper than its
predecessor. It will trace most pipes and ore veins at least
50 percent farther, and the new crystal controlled circuitry
is rock stable. The old metal-rim antenna is gone and so
are the hard-to-get batteries. The GEMINI-3 is easier to use,
two pounds lighter, & features Voltage Controlled Oscillator
(VCO), audio target response for precision pinpointing.
Your Fisher GEMINI-3 is a high quality, precision instrument
engineered by the oldest and proudest name in metal
detectors. Treat it right, read this instruction manual thoroughly
and practice often. Who knows, with skill, patience and a
little luck, you may nd the BIG ONE.
Drop us a line if you have any questions, comments or
exciting GEMINI-3 stories. In the meantime . . .
Happy hunting,
FISHER RESEARCH LABORATORY
22
SPECIFICATIONS
Dimensions
Length on handle ............................................................49 1/2 inches
Transmitter-Receiver Box Assembly
.................................................9 1/4 x 12 x 6 inches(23.5 x 30 x 15 cm)
Weight
Complete ...........................................................................7 lbs. (3.2 k)
Transmitter ........................................................................2.4 lbs. (1.1 k)
Receiver ...........................................................................2.9 lbs. (1.3 k)
Handle ..............................................................................1.7 lbs. (.75 k)
Frequency
RF Search and Trace ............................81.92 KHz Crystal Controlled
................................................. Audio Target Response (VCO)
Operating Modes
Search
1. Narrow Scan, Inductive
2. Wide Scan, Inductive
Trace
1. Inductive
2. Conductive
Target Response
Meter ......................................................2 1/4 x 1 3/4 inches, Analog
Speaker ............................................................2 1/4 inches, 100 ohm,
Moisture Proof Cone
Headphones ..........................................1/4 inch Jack, 8-16 ohms,
............................................................................................Stereo/Mono
Batteries
Receiver .............................................................................. (8) AA 1.5V
Transmitter .......................................................................... (8) AA 1.5V
Life ...........................................Carbon Zinc ............................30 Hours
.................................................Alkaline ....................................50 Hours
2
3
4
5
62
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4
BASIC THEORY OF OPERATION
The GEMINI-3 was engineered to detect conductivity
changes in the earth over which it is carried. Hence, a positive
response by the GEMINI-3 indicates the presence of a metal
object, ore vein or mineral that is more conductive than the
surrounding rock or soil.
The function of the GEMINI-3 Transmitter is to send a radio
frequency (RF) signal down to a conductive object and
generate an electromagnetic eld around that object.
When used in any of the Inductive modes, the RF signal
travels through the ground to the object. When used in
the Conductive Trace mode (see page 13), the signal is
transmitted directly through a wire attached to an exposed
portion of the object.
The function of the GEMINI-3 Receiver is to locate the
object by detecting the electromagnetic eld around it and
responding with audio and visual signals.
21
National Forest and Federal Lands—Metal detecting is allowed
only by special permit acquired from the federal government.
Each area has a district ofce.
Corps of Engineers, Lakes, Shorelines and Lands—Permission has
been granted only on predisturbed sites, such as beaches and
attached swimming areas. New Corps lakes and lands must be
okayed by the main ofce of the Army Corps of Engineers. Each
area has a district ofce.
State Parks and Lands—Some state parks are open to metal
detecting, but some are not. Always check with the park ranger
before attempting to use your detector.
Bureau of Land Management (BLM) Lands—Some areas are
open for metal detecting, and some are not. Always check with
the district ofce.
City or County Park Lands—Most are open to metal detecting
unless notice is given by a sign or city ordinance. When in doubt,
always check with the city’s Parks and Recreation Department.
Public School Grounds—Most are open to metal detecting unless
notice is given by a sign, city ordinance, law enforcement ofcial,
or school employee. You should always check with the school
ofce rst.
Privately Owned Lands (Private Property)—Permission required. It
is always best to have the permission in writing.
Historically Marked Lands or Sites—Metal detecting is not
allowed. Don’t even think about it.
Where To Use Your Metal Detector In The U.S.
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5
DEPTH
The GEMINI-3 was designed to locate large, deep objects such
as an iron chest, pipe or an ore vein. It will not detect small coin-
sized objects. A quart jar full of coins, however, may be detected
one-to-three feet deep. A 55-gallon drum may be detected as
deep as 10 feet. A very large object, like an automobile, may be
detected at 20 feet or more.
The ability of the GEMINI-3 to detect objects at various depths
depends on several factors:
1. Ground Mineralization: The penetrating power of the
GEMINI-3 is adversely affected by the presence of
magnetite (a black iron oxide) and wet conductive
mineral salts. For example, an object that can be
detected at 15 feet in neutral ground may be
detected no deeper than 5 feet in highly mineralized
ground.
2. Size and Depth of Object: A 4-inch diameter target
will produce signal 64 times stronger than a similar
1-inch diameter target at the same depth. An object
1-foot underground will produce a signal 4,000 times
greater than the object 4 feet deep.
3. Length of Time Object is Buried: An object that has
been buried for a long time may be easier to detect
than a newly buried object. Rust and other oxides as
well as mineralization caused by the interaction of
the metal with soil chemicals are good conductors
and aid detection.
4. Shape of an Object: Ring or looped shaped objects
lying at produce the best results. Flat or dish shaped
targets are also easy to detect. Rod shaped objects,
especially when scanned on end, are very difcult
to detect.
5. Operator Skill: Probably the most important factor of
all, practice over known buried targets is essential.
20
LETS PRESERVE OUR TREASURED SPORT!
Laws governing the use of metal detectors are becoming
more and more common. In many countries, the use of metal
detectors is illegal or severely restricted. Don’t let this happen in
your area.
ALWAYS get permission to hunt on private property.
ALWAYS leave a site cleaner than you found it. Take at least
some trash with you or, if you can, take it all.
ALWAYS ll in your holes neatly whether you’re in a city park
or remote wildernessness. Leave the land as it was before you
disturbed it.
ALWAYS obey all laws relating to Treasure Hunting.
ALWAYS return valuable property if you can locate the original
owner.
ALWAYS do whatever you can to give the hobby of Treasure
Hunting the good image it needs and deserves.
TREASURE HUNTERS’ CODE OF ETHICS
Gemini-3manual-.ind2 5 6/13/06 2:52:51 PM
TRANSMITTER
Battery Level Meter
Power Switch Ground Plate
Jack
Figure 2. Transmitter
Power Switch: Pull out switch turns on power.
Ground Plate Jack: Used with the optional Ground Plate Assembly
for the Conductive Trace Mode.
Battery Level Meter: Gives a visual indication of battery strength.
Replace batteries if below 5 on meter.
619
BATTERY REPLACEMENT
1. Turn either instrument (Transmitter and Receiver) over
on its face and remove access plate with coin or large
blade screwdriver.
2. Lift the battery pack out carefully. Turn the battery
pack slightly, unsnap the battery connector and slip
off the sleeve. Change all eight batteries. Slip the
sleeve back on, then reattach the connector to the
pack. Slip the battery pack back into its compartment
and do a battery test. Refasten the access plate.
Both the transmitter and receiver will work from 30 to
40 hours on a set of 8 standard quality, carbon-zinc
batteries. Alkaline batteries will give substantially
longer life and in cold weather will perform much
better than standard carbon zinc batteries.
NOTE: As supplied from the factory, the battery pack is
surrounded by a plastic sleeve to retain the batteries during
possible rough handling and shipping. As a precaution, always
reinstall the sleeve after battery replacement.
Figure 10. Changing Batteries
Gemini-3manual-.ind2 6 6/13/06 2:52:51 PM
RECEIVER
Speaker: Provides audible indication of the receiver signal for
balancing and detecting.
Meter: Provides visual indication of the Receiver signal response for
balancing and detecting. Also used as a battery test indicator.
Sensitivity Control: Used to control sensitivity level. The circled “7”
indicates the starting level used for Narrow Scan Inductive Search
Mode.
Headphone Jack: Accepts stereo or monaural headphones and
silences speaker when headphones are plugged in. (Stereo/mono
headphones should be in “stereo” position.)
Power Switch: Pulling switch out turns on receiver.
Meter
Sensitivity
Control
Headphone Jack
Power Switch
Speaker
Figure 3. Receiver
Battery
Test Switch
7
18
PROSPECTING TIPS
Sources of Error
The most common nonproductive zones of
conductivity are:
1. Dissolved mineral salts - Mineral salts become
conductive when dissolved in water. As a result, the
presence of saline water or water saturated soil high
in salt content, may render the GEMINI-3 useless.
2. Rough terrain - In very rough terrain it may be difcult
to maintain the GEMINI-3 parallel to the ground,
resulting in frequent false signals.
3. Irregularities in the overburden bedrock - The GEMINI-
3 may detect sharp changes in conductivity which
are of no important geological signicance.
4. Fault zones - Fault zones often give positive indications
because they are highly fractured and usually contain
concentrations of water and minerals.
5. Alluvial deposits along creek bottoms - Conductive
deposits along creek beds usually have no economic
value or importance in determining the geology.
6. Conductive debris - Unexpected high readings are
often due to highly conductive debris near the
surface such as scrap iron, tin cans, etc.
7.
Magnetite - Heavy concentrations of magnetite will
cause false signals and/or loss of penetrating power.
It is obvious from the above that every response
by the GEMINI-3 does not indicate the presence
of valuable ore, but rather an indication that the
earth’s conductivity has changed. It remains for the
operator to properly interpret this data. The successful
prospector will have some understanding of the ore
he is seeking and of the existing geological conditions.
The successful operator will also have studied that
area and will know in advance what ore he is seeking
and where the best opportunity exists for locating it.
Under these conditions, the GEMINI-3 can provide
valuable information. On the other hand, random
wandering and prospecting for no ore in particular
can be an expensive waste of time.
Gemini-3manual-.ind2 7 6/13/06 2:52:52 PM
8
SEARCHING
Narrow Scan Inductive Search
This mode of operation is performed by a single operator using
the 3-piece handle. It is the best method for locating small or short
objects (chest, coin-jar, rie, etc.). However, it is also an effective
way to locate pipes, cables and ore veins.
Set Up 1. Assemble the 3-piece handle by inserting each
end piece into the center handle section. Tighten
the two center knobs nger tight until there is no
wobble. Place the transmitter on its back and
insert the end of the handle with the single brass
shaft into the V-shaped slot. Turn the knob until it is
nger tight and the handle is rmly in the slot.
2. Align the receiver panel holes with the upper-
handle threaded shafts. Tighten the lower black
knob until it is nger tight.
3. Turn the balance knob (with white arrow) until the
spring is under tension (at least 10 turns).
Figure 4. Narrow Scan
Inductive Search
Figure 5. Assembly for Narrow Scan Inductive Search
17
PROSPECTING TIPS
Mapping When an area of high conductivity is encountered,
outline and stake it by crossing and recrossing, using
the Narrow Scan Inductive Search mode. It will be
noted that in and near the conductive zone, a
maximum indication will be received in only one
denite direction when the operator stands at one
point and rotates the instrument parallel to the surface
of the ground. Record the meter readings as read
in the maximum directions, at various points along
the zones. Note the character of the overburden,
outcrops and topographic features.
When the area being inductively surveyed has been
completely covered and all of the conductive zones
have been staked, these zones are surveyed and
plotted on a map. The map should include all creek
bottoms, gullies, outcrops and other physical features.
The ideal map on which to plot the conductive zones
is a topographic and geological map of the proper
scale. In this way it is possible to correlate the zones
directly with the topography and geology, and thus
determine the possible reasons for the presence of
the various conductive zones.
Locating Placer Deposits
A lot of prospectors have told us they would like to
use a two-box for locating placer gold. In general,
these deposits contain such a small amount of gold
that it cannot be detected. Placer gold, however,
is usually associated with a certain amount of black
sand, and some placer deposits carry iron sulphide.
Both of these mineral substances are definitely
conductive, and may be detected by the GEMINI-3.
It is through the detection of these minerals that the
placer gold may be located.
Gemini-3manual-.ind2 8 6/13/06 2:52:52 PM
9
Tuning 1. Set the transmitter:
Power: ON
2. Set the Receiver:
Power: ON
Sensitivity: 7
You should get a strong audio tone and meter
indication at this point.
CAUTION: Never attempt to tune the GEMINI-3 in the
presence of metal objects likes cars, metal walls, roofs
or heavy metal reinforcements in any structure. Their
presence will make proper balancing impossible.
3. Pick the unit up by the handle and balance it so that
it is level with the ground and at normal carrying
height (arm’s length). Five cm higher in the front is
OK. For a deeper search, attach the fully lengthened
carrying strap to the eyelets at the ends of the handle
(see illustration on page 9). You will need to hold
the instrument at this lower level while tuning if you
plan to use it lowered. On some highly mineralized
ground and some asphalt, you may not be able to
use it with the strap fully lengthened. You will know
this during tuning if you cannot reach a silence (null).
Not reaching a null can also indicate the presence of
nearby metal. If this is the case, move away from the
metal to balance your GEMINI-3 to the ground only.
4. Still holding the GEMINI-3 parallel to the ground, slowly
turn the BALANCE knob (with arrow) on the three-
piece handle counterclockwise until you get silence
(null) and zero meter reading. At this point there
should be no sound as you rotate the knob 1/8- to
1/4-turn further counterclockwise before reaching
sound and meter reading again.
5. If you cannot null the audio or your null point is less than
1/8 turn, reduce SENSITIVITY slightly and try again.
6. If you can turn the BALANCE knob more than 1/4 turn
without an increase in the sound or meter, increase
SENSITIVITY slightly and try again. Keep adjusting as
described until 1/4 turn of silence (null) is achieved.
SEARCHING
16
Tuning 1. Set the transmitter:
Power: ON
2. Set the receiver:
Power: ON
Sensitivity: ZERO
3. Slowly increase the SENSITIVITY control until the
audio signal is heard, then reduce SENSITIVITY until
the audio just disappears. This is the point at which
air coupling has been eliminated.
Operating 1. Locate the buried pipe by circling the contact
point, keeping the receiver in line with the contact at
all times. Stay at least 30 feet from the transmitter.
2. Once the pipe has been located by a sharp
increase in audio and meter signals, the pipe may be
traced exactly as described in the operating section
of the Inductive trace instructions.
3. Be aware that a nonconductive gasket in the pipe
will terminate the RF signal from the transmitter.
TRACING
Figure 9. Conductive Trace
Gemini-3manual-.ind2 9 6/13/06 2:52:52 PM
10
SEARCHING
7. You are ready to search when the BALANCE knob
is adjusted within the 1/8- to 1/4-turn silence (null)
space. This is extremely important! If this procedure
is not followed correctly, the GEMINI-3 will either
constantly give false audio and meter readings
(sensitivity too high), or no signals at all (sensitivity
too low). The sensitivity will be correctly set and your
GEMINI-3 will operate properly only when a 1/4- to
1/8-turn null has been achieved. If you lower or raise
your GEMINI-3, you may have to retune by making
repeated adjustments to the BALANCE knob and/or
the SENSITIVITY control.
Operating
1. Test your GEMINI-3 in an area you are reasonably sure
is free of large buried objects. Scatter some metal
objects, such as a tool box, piece of pipe.
2. With the instrument properly tuned and held in the
hand or suspended by the strap, slowly walk directly
toward your test object. Keep the handle as level
and steady as possible while in motion or the tuning
may change and you’ll receive false signals and/or
lose sensitivity.
3. As you approach your target, the speaker sound
and meter indication will increase. They will reach
maximum readings when you are directly over the
conductor (target). Remember, on the GEMINI-3,
unlike earlier models, the sound volume and pitch
continue to increase after the meter pegs. This allows
you to pinpoint without constantly readjusting the
SENSITIVITY knob.
4. As you cross the target, the signal indications will begin
to decrease because you are moving away. To get a
precise x on the location, make a mark at your feet
when readings reach their maximum. Cross over the
target, turn around and come back. Make a second
mark when readings return to maximum. Your target
will be centered between the two marks.
15
TRACING
Operating
1.
Once the two starting points have been established and
the receiver tuned, walk away from the transmitter in
the assumed direction of the buried conductor.
2. Hold the receiver vertically to maintain a peak signal
or horizontally, face up, to maintain a null or minimum
signal. Either method indicates that you are over the
object and tracing its path.
3. As the distance from the transmitter increases, the
signal will fade. As this occurs, increase the SENSITIVITY
as required.
4. When the signal becomes too weak to trace, stop
and move the transmitter closer.
5. Be aware that if you are tracing a pipe, each time a
“T” junction or lateral is encountered, the signal will
split and weaken.
Conductive Trace
This is the best method for tracing a single pipe in the
presence of other pipes. A portion of the pipe must be
exposed in order to energize it by direct connection
utilizing the optional Ground Plate Assembly or
Ground Rod Assembly.
Set Up 1. If possible, clean the contact point of the pipe with
a wire brush.
2.
Connect the ground plate clamp to the contact point.
3. Plug the Ground Plate Assembly or Ground Rod
Assembly into the transmitter Ground Plate Jack.
4. Set the transmitter on the ground and in an upright
position as far away from the contact point as
possible, at right angles to the assumed direction of
the pipe or cable. Insert the Ground Plate or Ground
Rod Assembly in the ground as far away from the
transmitter as possible. Lay the Ground Plate at on
paved surfaces. Placing it in a puddle of water and
weighing it with a rock will help conductivity.
5. Hold the receiver vertically, in line with the contact
point of the pipe at least 30 feet away.
Gemini-3manual-.ind2 10 6/13/06 2:52:52 PM
11
SEARCHING
5. For even more accurate pinpointing of short objects,
(i.e., a pipe, cable, etc.) approach the test object
at right angles from your previous direction. Mark the
ground as you did before. Your test object should be
about centered between four marks.
6.
To establish the path of a pipe, cable, or other long
conductor, pinpoint two more locations 15-20 feet
apart. From these three locations you should be able to
draw a straight line (unless the pipe isn’t straight). Careful
additional locations may be necessary if no prints (maps
of underground lines) of the area are available.
7. It may be necessary to reduce sensitivity with the
SENSITIVITY knob when the pipe or cable is large and/
or shallow. If the meter needle has peaked and sound
is at a high level, you will want to bring the sensitivity
down to see the peak of the needle at a point less
than 100 as you move in half or quarter steps back
and forth to get your peak reading.
8. If at all possible, practice over some
buried targets of known size and depth.
9. There are several things to consider
when locating buried objects:
a. Precise location depends on operator skill.
b. Position of the ground marks does not
indicate size of the object or its path.
c. More than one metal object may cause
a wider or stronger response than
expected.
d. Deeper targets may not produce a signal
until the operator has passed directly over
them.
e. Reducing the receiver SENSITIVITY control
will narrow the area between the ground
marks for more precise pinpointing.
f. Small or deeply buried objects such as a
cache of coins, require a tight, closely
traversed search pattern. Large or shallow
objects can be located successfully with
a larger, more widely traversed search
pattern.
Figure 6. Handle strap: Using
the handle strap increases
depth; however, it may be
difcult to tune the GEMINI-3
this close to highly mineralized
ground.
14
TRACING
Inductive Trace
The Inductive Trace mode is usually used to trace
a long object (pipe, ore vein, etc.) that shows no
exposed portions, but two starting points are known.
Set Up Locate two points along the conductive object at
least 30 feet apart as described in the Wide Scan
or Narrow Scan Inductive Search sections. The
transmitter and receiver should be in line with each
other, both facing the same direction. The transmitter
should be on the ground and the receiver should be
held by the operator.
Tuning 1. Set the transmitter:
Power: ON
2. Set the receiver:
Power: ON
Sensitivity: ZERO
3. Increase the receiver SENSITIVITY control until you have
an audio response and at least a mid-scale meter
deection.
4. Determine that you are not direct air coupling by
moving the receiver back and forth. The audio meter
indications should peak over the object. No peak
will be observed if the receiver is too close to the
transmitter and direct air coupling is occurring.
Figure 8.
Inductive Trace
Gemini-3manual-.ind2 11 6/13/06 2:52:52 PM
12
SEARCHING
Wide Scan Inductive Search
This mode of operation is the preferred method for
searching a large area quickly. Two operators are
required and the handle assembly is not used.
The Wide Scan Inductive Search mode is practical
only when searching for ore veins, pipes or cable
40 feet long or more. If the operators are too close
together, “direct air coupling” will result, meaning
the receiver is detecting the Transmitter signal
directly through the air instead of through a buried
conductor.
Set Up Two operators line up at least 20 feet apart, one with
the receiver and one with the transmitter, parallel to
the assumed direction of the buried conductor. The
transmitter and receiver should be in line with each
other, facing the same direction.
1. Set the transmitter:
Power: ON
2. Set the receiver:
Power: ON
Sensitivity: ZERO
Figure 7. Wide Scan
Inductive Search
Tuning
13
SEARCHING
3. Slowly increase the SENSITIVITY control until the audio
signal is heard, then reduce SENSITIVITY until the audio
just disappears. This is the point at which “air coupling”
has been eliminated.
Operating
1. Keeping the receiver and transmitter sections in line,
the two operators can now walk their predetermined
search pattern. The SENSITIVITY control should be
checked periodically to ensure that the receiver is
tuned just below the “air coupling” threshold.
2. If both operators cross the same conductive body
(pipe, cable, ore vein, etc.) at approximately the
same time, the receiver tone and meter will rise to
indicate its presence. The receiver operator should
alert the transmitter operator that they have detected
a conductive object.
3. The receiver operator should then hold his position
while the transmitter operator moves back and forth
for the strongest receiver response. At this point,
the transmitter operator should stop and place the
instrument on the ground with the handle grip on
top.
4. The receiver operator can then pinpoint the buried
object by moving the receiver back and forth in line
with the transmitter. The object should be directly
beneath the point of maximum response.
5. The receiver operator may then trace the signal along
the length of the unseen object as described in the
Inductive Trace section (page 12).
Gemini-3manual-.ind2 12 6/13/06 2:52:53 PM
