Fisher Research Labs TW-6 User manual

TW-6

Pipe and Cable Locator

Operating Manual

F I S H E R R E S E A R C H L A B O R A T O R Y

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CONTENTS

Introduction ...............................................................................pg. 3

Receiver .....................................................................................pg. 4

Transmitter..................................................................................pg. 5

Component Descriptions .........................................................pg. 6

Modes of Operation .................................................................pg. 7

The Inductive Mode..................................................................pg. 7

How to Assemble ......................................................................pg. 7

How to Tune...............................................................................pg. 8

Inductive Locating (with handle)............................................pg. 10

High Power (with handle).........................................................pg. 11

Inductive Tracing (without handle) ........................................pg. 12

Inductive Locating When Only Approximate Position of a

Linear Conductor is Known......................................................pg. 13

Pinpointing Centering of the Pipeline.....................................pg. 13

Determining Conductor Depth by Triangulation ..................pg. 14

Locating Manhole Covers, Valves, Tees and Risers..............pg. 15

Locating Pipe When Other Lines are Close by......................pg. 15

Conductive Tracing (without handle)....................................pg. 16

Tracing Procedure ....................................................................pg. 18

The Tracer Probe .......................................................................pg. 18

The Coupling Clamp ................................................................pg. 19

Locating Non-Metallic Pipes....................................................pg. 20

Operating Hints .........................................................................pg. 21

Changing Batteries ...................................................................pg. 22

Specifications ............................................................................pg. 23

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INTRODUCTION

to set the standard of quality in the design and manufacture of

even greater speed and precision in locating underground pipes
and cables.

covers, manhole covers, or valves clearly visible at the surface of
the ground are excellent items to start locating. This way you will

WARNING: Batteries can contain hazardous materials and must
be disposed according to the laws in your country.

This Category II radiocommunication device complies with
Industry Canada Standard RSS-310.

Ce dispositif de radiocommunication de catégorie II respecte
la norme CNR-310 d’Industrie Canada.

3

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RECEIVER

1. Carrying Strap: Keeps one hand free for marking

ground or pavement while using Tracer Probe.

2. Meter: Indicates signal strength up to a point
from metallic conductors while locating or tracing.
Meter also gives a visual indication of battery
strength.

3. Accessory Input: Use this jack to plug in all
accessories except the headphones.

4. Sensitivity:

A. Toggle switch to select NORMAL or HIGH

range.
B. Knob to control sensitivity level within the
NORMAL or HIGH range.

5. Depth Level: This bubble indicates the angle of
the receiver to the ground. Use it to keep Receiver
and Transmitter level during Inductive Locating
and for making the 45-degree angle necessary in
depth determination.

6. Headphones: Use this jack to plug in
headphones only. It automatically silences
speaker. Use in particularly noisy areas.

7. Battery Test: Turn unit ON then press this red
button and observe battery strength on meter. If
meter reads below 80, replace receiver batteries.
Usually transmitter & receiver batteries are

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RECEIVER

replaced at the same time.

8. Power: Pull out for ON, push in for OFF.

9. Speaker: Produces the audible signal, which

increases in volume and pitch as signal strength
increases. The volume and pitch increase even
after the meter has peaked at 100.

TRANSMITTER

1. Battery Test Meter: Gives a visual indication of

battery strength. Battery test is activated
automatically when unit is turned ON.

2. Constant Signal/Warble Tone Switch:

A. When toggle switch is in left position a constant

signal is generated/transmitted.
B. When Toggle Switch is in right position, the TW6
generates a warble tone. This results in a pulsating
sound and an oscillation of the needle between
zero and 100.

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TRANSMITER

3. Accessory Output: The Ground Plate Assemblies

Coupling

Clamp or Ground Rod Assembly connects into
this jack for a Conductive Trace or Direct Induced
Trace.

COMPONENT DESCRIPTIONS

1. Ground Rod/Harness Assembly: Provides a

“ground” for greatest efficiency in CONDUCTIVE
TRACING. For hard ground, the accessory Ground­Rod /Harness Assembly is recommended.

2. 3-Piece handle: For use in INDUCTIVE LOCATING.

3. Handle Carrying Strap: Allows you to lower handle

closer to the ground for greater depth penetration
and sensitivity in locating. The same strap is used for
carrying the receiver.

4. Handle Carrying Case: Protects 3 piece handle
and makes a neater bundle.

5. Carrying Case: Sturdy protection for your TW­6 and storage for accessories, such as coupling
clamp, headphones, mini probe, and ground plate
assembly.

6. Headphones : Stereotype headphones are
available for the TW-6. They are switch selectable
from monaural to stereo and may not work with the
TW-6 when switched to mono. You may prefer to use
the stereo phones because volume is adjustable
separately to each ear. The VCO sound is shrill and
without a volume control on the mono headphones,
the sound may be uncomfortable.

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MODES OF OPERATION

and CONDUCTIVE. In the INDUCTIVE mode, the Transmitter

LOCATING and (2) Transmitter placed on the ground directly
above and in line with the conductor for TRACING and the path
of the conductor.

The CONDUCTIVE mode operates when you connect the
Transmitter directly to an exposed portion of the pipe or cable in
question with the Ground Plate Assembly, or with the Coupling
Clamp, or the Ground Rod Assembly.

THE INDUCTIVE MODE

HOW TO ASSEMBLE

1.

end sections into the central section and turn the

2. Place the Transmitter on its back and insert

3.

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MODES OF OPERATION

4. With the Transmitter still on its back, align the two

holes in the panel of the Receiver with the knobs.

5. Turn the lower knob of the two knobs until it is

spring is compressed and the panel is pulled within

HOW TO TUNE

1. Check batteries on bo t h Transmitter and

Receiver.

2. Place the Receiver Sensitivity Switch in the
NORMAL position.

3. Turn SENSITIVITY knob to 7.

4. To turn ON, pull POWER switches on Receiver and

Transmitter.

5. Pick the unit up by the handle and balance it so
that it is level with the ground and at normal carrying
height (arms length). For a deeper search, hold with
the carrying strap which has been fully lengthened.
You will need to hold the instrument at this lower level
while tuning if you plan to use it lowered. On some

may not be able to use it with strap fully lengthened.

reaching a null can also indicate the presence of
nearby metal.

CAUTION: Never attempt to tune the TW-6 in the presence of metal
objects like cars, metal walls, roofs or heavy metal reinforcements
in any structure. Their presence will make proper balancing
impossible.

6.

lowest meter and speaker indications are reached.

in either direction results in an increase in sound and
meter reading. If at the lowest point there is still sound

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MODES OF OPERATION

and meter reading, turn down sensitivity slowly until

without an increase in sound and meter reading,
turn the sensitivity knob up from 7 to 8 and try again,
going through the null area making sure it does not

balance.

CAUTION: Keep away from cars, fences and metal
objects during this procedure.

metal causes an increase in sound and meter
reading.

You are now ready to locate. Crossing over buried

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MODES OF OPERATION

INDUCTIVE LOCATING (with handle)

locate lost or unknown metal pipes and cables. Walk at a right
angle toward what you assume to be the conductor’s position. As
you near the conductor, the speaker sound and meter indication
will increase. They will reach maximum readings when you are

earlier models, the sound volume and pitch increases far higher
than when the meter peaks. This will allow you to do most of your
locating without several readjustments of the Sensitivity knob.

As you cross over, the indications will begin to decrease because

a mark at your feet when readings reach their maximum. Cross
over the pipe, turn around and come back. Make a second mark
when readings return to maximum. Measure between the two
marks and bisect the distance. That is where the conductor is.

three locations you should be able to draw a straight line (unless
pipe has turned). Careful additional locations may be necessary
if no prints of the area are available.
It may be necessary to reduce sensitivity with the knob when the

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

your peak reading.

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MODES OF OPERATION

HIGH POWER (with handle)

and an earlier model is that you may prefer to use it in HIGH power,

no sound when balancing. As you approach a pipe or cable lying
beneath the ground, the signal may be slight, approximately 20

Now turn the Sensitivity knob up so the meter reading becomes

a peak on the meter. Mark the spot on the ground where you
have stopped, with both feet together. Then go on beyond the
conductor, turn around and approach the conductor in the same
way, stopping with feet together at the highest meter reading and
mark the spot on the ground. Measure between the two points,
bisect it and you have the centerline of the conductor.

Be aware that when you use HIGH power on the handle, you will
need to be further away from vehicles, metal buildings and metal
fences to avoid sensing them as well.

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MODES OF OPERATION

INDUCTIVE TRACING (without handle)

signal strength by having the bottom edge of the Transmitter
directly over and in line with the conductor you’re tracing. Placing

the conductor and a signal on either side.

If you place the transmitter and receiver too close together “direct

control down until you lose the air signal, or (2) simply move the
receiver further away until the air signal fades.

NOTE: With the SENSITIVITY knob on full and the Sensitivity Selection
Switch set to NORMAL, the two units should be at least 30 feet
apart to avoid air coupling. With HIGH SENSITIVITY, they must be
even further apart.

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MODES OF OPERATION

INDUCTIVE LOCATING WHEN ONLY APPROXIMATE POSITION

OF A LINEAR CONDUCTOR IS KNOWN

unit with its face towards him and parallel to the other’s instrument.

from the curb toward the opposite side of the street. When the
two operators are directly over the pipe, the receiver meter and
speaker will indicate the location. The pipe is directly below the
point at which the maximum signal occurs.

If only one operator is available, he should begin by placing the
transmitter over and in line with an assumed position of the buried

the transmitter, hold the receiver parallel to the other instrument
and begin to walk forward until the signal reads its maximum

move the transmitter several times in order to be precisely over
the buried conductor.

PINPOINTING CENTER OF THE PIPELINE

After determining the position of the pipe, set the transmitter down
on its bottom edge and in line with the indicated position. Then, at

down and begin moving the receiver from side to side over the
general location line of the conductor. This back and forth motion
will give a null directly over the position of the buried conductor.

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MODES OF OPERATION

DETERMININING CONDUCTOR DEPTH BY TRIANGULATION

This procedure is only accomplished when the transmitter is close
enough for the receiver to receive a strong and clear signal.

Once you have determined the exact centerline of the conductor
(either Inductively or Conductively), place the receiver above and
parallel to it. Hold the receiver as close to the ground as possible.
Now, tip the receiver back until the bubble inside the depth level
indicator rests between the outer edge of the center ring and the
black border of the level.

ground. Care should be taken at this point, as a few degrees of

conductor centerline. Now, back away slowly, at a right angle
to the conductor, keeping the bubble as steady as possible. The
meter indication should manually be adjusted by means of the
sensitivity control to stay on scale in order to observe the point
where the needle will fall to a minimum signal. After this point, the
signal begins to increase again.

Position the receiver at the minimum or null point. Measure the

of the fastener, which holds transmitter and receiver together. This
distance, minus the distance of the center of the locator loop

If the conductor is buried in sloping ground, make a depth
determination on each side of the conductor and average the

A tracer probe with its smaller receiver coil in the tip, is quicker
and easier to use, hence it yields greater accuracy in depth

when using the receiver or receiver with tracer probe.

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MODES OF OPERATION

LOCATING MANHOLE COVERS, VALVES, TEES AND RISERS

These jobs are best performed in the Inductive Mode using the

of the previously discussed methods, then, holding the center of
the handle with the receiver leading (face up), walk alongside the
main pipe. Be sure you’re far enough away from the centerline of
the pipe to have a low or no reading. When you cross the sought
after valve, tee or riser, the meter and speaker will signal a larger
mass of metal indicating the valve. At that point, you can cross

to pinpoint its location.

feet apart. Practice this grid technique with a visible cover so that

LOCATING PIPE WHEN OTHER LINES ARE CLOSE BY

method, set the transmitter vertically and parallel to the line to

tracing and away from the pipe not wanted.
Now, follow normal Inductive Tracing instructions. To locate the

feet away from the second pipe. In the second method, set up
the transmitter so that its plane points toward the pipe desired.

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MODES OF OPERATION

CONDUCTIVE TRACING (without handle)

The most satisfactory method of tracing when you need to trace
an individual pipe when another pipe is nearby is CONDUCTIVE

pipe through direct connection. Before attaching the ground rod
clamp to the conductor, clean the conductor with a wire brush

After cleaning, plug the jack into the transmitter and secure the

in an upright position and as far away from the pipe as possible to
the side opposite any other lines. As far away as possible means

If you are working in an area with several other conductors near
the pipe or cable you want to trace, place the ground plate as
close as possible to the point at which you fasten the clip to the
pipe or cable. This will reduce the signal strength and reduce the
amount of signal induced into another nearby conductor, giving
a more concentrated signal in the pipe or cable you are tracing.
Never stretch the ground plate across a conductor running parallel
to the pipe or cable you are tracing, because even if you are
not hooked up to the conductor you crossed over, the signal has

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MODES OF OPERATION

to cross back past the path of this conductor and will induce a
certain amount of signal into it. This signal can mislead you when
tracing it out.

Harness Assembly on its side, parallel to the conductor in
the direction of the tracing. Weighting it down with a rock or
someone standing on it makes it a better ground contact. If the
plate is weighted down in a puddle or at least if the pavement
is wet, tracing distance is improved. You may pour some water
on the pavement to improve ground contact.

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TRACING PROCEDURE

Turn the transmitter ON and turn receiver SENSITIVITY knob all the
way up in NORMAL. Then, when the conductor is located, turn
SENSITIVITY down to get a precise indication of the location. Use
NORMAL for ordinary tracing, HIGH for extended tracing. In the
Conductive Mode, you can have Transmitter and

Receiver as near to each other as 20 feet apart and closer yet
if you use the Tracer Probe, without air coupling occurring. With
HIGH power, the distance increases.
With settings and connections completed, the operator need only
walk out his trace while paying attention to signal strength over
the conductor. As in the Inductive Mode, the receiver should be
carried vertically and parallel to the pipe or cable being traced.
However, once the position is discovered, you may turn the

its surface location on pavement with colored chalk or spray paint
as you locate it. Extra long yellow or white golf tees are very handy
markers when locating over turf or open ground.

Another tip...start tracing operations away from the congested
location. The pipe is then carefully traced into the desired area
with little chance of false indications. The Tracer Probe also helps
reduce spurious signals from nearby pipes and cables.

The Tracer Probe

As you trace out the pipe or cable, signal strength gradually
diminishes. When you reach the limit of NORMAL, switch to HIGH
sensitivity and adjust the sensitivity knob for a sharp null over the
conductor you are following.

than the earlier model and does not need a separate SENSITIVITY

Tracer Probe

tracing distance.

back away at right angles, dragging the tip of the Tracer Probe
on the ground and maintaining the level bubble centered in its

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TRACING PROCEDURE

circle. You need to be close enough to the transmitter for a strong

then resume again as you move backwards. You measure from
the middle of the null area back to the centerline of the pipe or
cable and that is its depth.

COUPLING CLAMP

using the ground rod assembly, so there is no advantage to using

prevents bare metal contact.

Begin by plugging the Clamp into ACCESSORY OUTPUT on the
transmitter. Place Clamp around cable or other conductor (make
sure jaws are completely closed). Turn receiver and transmitter ON
and precede using tracing techniques as described earlier. The
conductor must make a closed loop, or circuit, or be grounded
for best tracing results.

driven into the ground to be sure of the ground. Two Coupling

receiver ACCESSORY INPUT jack. Then, test different strands with

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LOCATING NON-METALLIC PIPES

the ground plate assembly. Attach the ground plate assembly

or receiver and tracer probe. B lockages in pipes can be
located this way too in that the tracing signal will stop where

is aluminum foil tape sandwiched in printed mylar is available

laid according to the tape manufacturer’s instructions, the tape
and hence pipe can be located Inductively or Conductively.

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OPERATING HINTS

To develop your operator technique, practice with known

Of particular importance in this regard is the SENSITIVITY knob.
Learning to vary the SENSITIVITY knob and studying the effects of
those variations remains the key to getting the most precision out
of the instrument. These practice sessions will not only allow you to

cables, but it will also teach you how to interpret each reading.

SOIL (those with high mineral salt content and usually rather
damp), it may be necessary to turn down the SENSITIVITY control
from the suggested position. With each repeated reduction, the
operator should readjust the front knob as given in the “How To

sharply decrease the width of indication by tuning the SENSITIVITY

will allow more accurate pinpointing.

more noticeable at extended tracing ranges. Be sure that when

slowly enough for the receiver to sense the signal emitted by the
underground pipe or cable.

If the signal remains reasonably strong as you are tracing out a
pipe or cable and it mysteriously disappears, use the “null method

will give you greater tracing distance, however, usually the signal
method will give a longer trace.

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CHANGING BATTERIES

Turn the instrument over on its face (position is the same for both
transmitter and receiver) and remove access plate with coin or
large blade screwdriver.

Lift the battery pack out carefully. Turn the battery pack slightly
and unsnap the battery connector. Change all eight batteries.
Then reattach the connector to the pack. Slip the battery pack
back into its compartment and do 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 AA batteries. Alkaline batteries will give
at least 30 to 40% greater life. In cold weather, alkaline batteries
are much livelier than standard carbon zinc batteries.

WARNING: Batteries can contain hazardous materials and must
be disposed according to the laws in your country.

CAUTION: Do not try to recharge the batteries that come with the
TW-6, or any other batteries, except Ni-Cad rechargeables.

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SPECIFICATIONS

Transmitter Receiver

Operating Frequency......... 81.92 kHz +.005% ..... 81.92 kHz +.005%

Batteries................................8 each, AA (NEDA 15) 8 each, AA

(NEDA 15)

Weight ..................................2 1/2 lbs. (1.1 kg) ......... 3 lbs. (1.36 kg)

Sensitivity ..............................N/ANormal: 400 uV typical High: 8 uV

typical

Signal-to-noise ratio ............N/A ............................................. 110dB

Headset Impedance..........N/A ......................... 600 ohms (mono)

N/A.............................. 8 ohms (stereo)

Dimensions ...........................11 1/2” x 9” x 3...........11 1/2” x 9” x 3”

(29 x 23 x,.7.6 cm)................(29 x 23 x 7.6 cm)

Operating Temperature.....-1O0F to +1200F, (-230C to +480C)

depending on batteries used.

Total Weight.........................5 1/2 lbs. (2.5 kg)

-(without handle or accessories, ground plate assembly or operating manual).

Total Shipping Weight...............................................6 3/4 lbs. (3 kg)

-(including only ground plateassembly and operating manual.)

Total Shipping Volume....................................69 cu. ft. (119.5 liters)

Field Strength: 17.5dBuV @ 300 meters, 81.92KHz.

USING HEADPHONES

Using headphones (not supplied) improves battery life, and
prevents the sounds from annoying bystanders.
It also allows you to hear subtle changes in the sound more
clearly, particularly if searching in a noisy location. For safety
reasons, do not use headphones near traffic or where
other dangers are present. This device is to be used with
interconnecting cables/headphone cables shorter than three
meters.

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Q U A L I T Y

Fisher detectors are renowned for their quality.

Each detector is hand crafted in the USA with pride

P E R F O R M A N C E

The worldwide underground utility industry relys on Fisher.

Our instruments are durable, dependable, and locate deeper.

R E P U T A T I O N

over 70 years, the Fisher logo has been a mark of excellence.

2 - YEAR LIMITED WARRA NTY

Fisher believes in the products we produce and backs this belief

with a 2 year limited warranty.

Proof of purchase is required to make a claim under this warranty.

NOTE TO CUSTOMERS OUTSIDE THE U.S.A.

This warranty may vary in other countries, check with your distributor for details.

Factory warranty follows the channel of distribution.

Warranty does not cover shipping costs.

not expressly approved by the party responsible for compliance could void

the users authority to operate this equipment.

S E R V I C E

Fisher is committed to providing you, our valued customer, 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:

FISHER RESEARCH LABORATORY

FRL#8700241

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07-21-10