TW-8800
Operating Manual
Multi-Frequency Digital Line Tracer
F I S H E R R E S E A R C H L A B O R A T O R Y
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
Fisher produced the rst patented metal detector in 1931. For
over 70 years, the Fisher logo has been a mark of excellence.
2 - YEAR LIMITED WARRANTY
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.
According to FCC part 15.21 Changes or Modications made to this device
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
1465-H Henry Brennan,
El Paso, Texas 79936
Tel 915.225.0333 Fax 915.225.0336
www.sherlab.com email:info@sherlab.com
8708001 04-08-10
Description .................................................................................pg. 3
Transmitter .................................................................................pg. 5
Receiver .....................................................................................pg. 6
Accessories ................................................................................ pg. 8
Operating Instructions ..............................................................pg. 9
Depth Accuracy .......................................................................pg. 12
Specications ............................................................................pg. 13
Using Headphones ....................................................................pg. 14
Treasure Hunter Code of Ethics ............................................... pg. 14
CONTENTS
NOTES
2 15
DESCRIPTION
The TW-8800 Multi-Frequency Line Tracer consists of a transmitter,
receiver, ground-plate/ground-rod assembly, a carrying case, and
an operators manual. The TW-8800 has both active and passive
locating features.
1
3
Active locating utilizes both the transmitter and the
receiver. By applying a signal with the transmitter,
the operator can trace the path of the utility with
the receiver. Different utilities respond better to
different frequencies, and the TW-8800 has three
frequencies the operator can choose from: 82 kHz,
8.2 kHz, and 820 Hz.
There are three methods of active locating that an
operator can use to trace a utility. The conductive
method is the most preferred method, since a strong
transmitter signal is transmitted through the intended
target. The operator can choose any of the three
frequencies to trace the utility. The type of utility
being traced would be the determining factor as to
which frequency to choose. The inductive method is
the easiest method to use, but may not yield the best
results. When a direct connection is not available,
but the operator has good knowledge of where one
point of the utility may be, the operator can place
the transmitter over the utility making sure that the
arrow on top of the transmitter is parallel to the path
of the utility. Inductive locating can be done at the
82 kHz and the 8.2 kHz frequencies. The third method
of active locating involves using the coupling clamp
accessory. The coupling clamp is used when the
utility is exposed, but a direct connection is not
available. The clamp jaws are opened and placed
around the utility. The clamp never makes a direct
connection with the utility; that is, the utility can
move freely with the clamp around it. This method
can only be used at the 82 kHz frequency.
14
Laws governing the use of metal detectors are common in some
areas. In many countries, the use of metal detectors is illegal or
severely restricted. DON’T LET THIS HAPPEN IN YOUR COUNTRY!
• Always check Federal, State, County and local laws before
searching.
• Respect private property and do not enter private property
without the owner’s permission.
• Take care to rell all holes and try not to leave any damage.
• Remove and dispose of any and all trash and litter found.
• Appreciate and protect our inheritance of natural resources,
wildlife and private property.
• Act as an ambassador for the hobby, use thoughtfulness,
consideration and courtesy at all times.
• Never destroy historical or archaeological treasures.
• All treasure hunters may be judged by the example you set;
always conduct yourself with courtesy and consideration of
others.
LET’S PRESERVE OUR TREASURED HOBBY
TREASURE HUNTERS’ CODE OF ETHICS
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 trafc or where
other dangers are present. This device is to be used with
interconnecting cables/headphone cables shorter than three
meters.
USING HEADPHONES
DESCRIPTION
4
The passive locating method utilizes only the receiver.
This method of locating uses signals that are inher-
ently associated with the utility. The TW-8800 has two
modes for passive locating: 50Hz/60Hz (power) and
14 kHz to 30 kHz (radio). The power mode senses the
electromagnetic elds on energized electrical lines.
The radio mode senses the re-radiated radio waves
that are occasionally associated with utilities. Often
these signals are weak, so to assist the operator, we
added a feature that oscillates the signal, thus allowing the signal to be heard.
The features of the TW-8800 make it a very versatile
and practical instrument in today’s world of under-
ground locating.
SPECIFICATIONS
Subject to improvement or modication without notice.
13
Depth Accuracy .....................+1 inch per foot in nominal conditions
Readout Units ..........................Inches or cm (factory preset)
Left/Right Guidance ............... Audio: continuous tone=Left,
pulsed tone=Right. VCO (varying pitch) output for easy over
target location. Visual: Left/Right/Over Target messages
Signal Strength ......................... Digital Numeric Readout (0-99%)
& Bar Graph
Sensitivity Adjust....................... Automatic
LCD Backlight ..........................Included
Battery Test ............................... Automatic Low Battery alert
Push button readout
Battery Type ............................. Six “C” cells
Battery Life ...............................80 Hours
Weight ...................................... 6.0 lbs.
Operating Temp ...................... -4 0 to +1400F (-200 to +600C)
Output Frequencies ................ 82kHz, 8.2kHz, 820Hz
Output Power (nominal) ........ 82kHz: .7Watts, 8.2kHz: 7.0Watts
820Hz: 7.0Watts
Battery Test ............................... Yes
Battery Type ............................. Two 6 Volt lantern batteries
Battery Life ...............................80 Hours at 82kHz
Weight ...................................... 7.8 lbs.
TRANSMITTER
RECEIVER
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.
TW-8800 TRANSMITTER
5
Located on the transmitter are the power mode and
the frequency selector. The power mode enables
the operator to turn the transmitter on or off, and to
check the condition of the batteries. When checking the batteries, a reading of 50 or greater on the
display meter indicates that batteries are usable.
Battery usage is dependent upon the frequency
that is being used. The higher the frequency, the
longer the battery life. The frequency selector is
used to select the transmitted frequency. Only one
frequency can be selected for transmission.
Other items on the transmitter include the plug-in
socket for the ground plate/ground rod assembly,
and for the coupling clamp. There is a Red LED that
blinks when the transmitter is on. The batteries are
located underneath the lid on top of the Transmit-
ter housing.
Transmitter
WARNING: Do not handle output leads unless power is off.
ELECTRIC SHOCK HAZARD: Servicing to be performed by
qualied personnel only.
DEPTH ACCURACY
Depth measurement is a feature of the TW-8800. Accuracy is
dened on an ideal target; that is, one that is continuous, a good
conductor, and not surrounded by other utilities. There are several
factors that can cause the operator to question the accuracy of
the utility being traced.
Inductive Transmitter Setup
Inductively, only a small portion of the signal attaches itself to the utility. With a weakened signal, trace should be
accurate, but depth may not. The conductive method
will yield better results.
Low Receiver Signal Strength
When the signal strength falls below 20 – 25%, depth
readout may not be accurate. It would be benecial to
move the transmitter to a closer point of contact.
Nearby Utilities
Close, nearby utilities may have some inuence on the
accuracy of the Depth readout. This is more prone to
happen in the higher frequencies where signals can jump
to nearby utilities. Switching to a lower frequency can
give better results.
Moisture
Ground that is too dry or overly saturated may skew the
depth readout.
“T’s”, elbows, or splits in the utility can distort the
transmitted signal in that general area.
12
WARNING: Do not connect output leads to a live (ener-
gized) utility. Please prevent shock hazard and equipment damage.
The TW-8800 Transmitter.
6
Receiver
Mode
Allows the operator to change frequencies. By depressing this key, the receiver will cycle through the active and
the passive frequencies. The selected mode is shown on
the left side of the display screen.
Power On/Off
Turns the receiver on or off.
Light
Lights up the display for usage in dark areas. When the
display is backlit, LIGHT is shown on the bottom left hand
side of the display screen.
Bat
Press and hold this pad to check the battery level of the
receiver. A bar graph on the right side of the display
will give status of the batteries. When the graph shows
1 bar, it is time to replace the batteries. Additionally, as
the operator uses the Receiver, if the batteries get low,
REPLACE BATTERIES will appear in the lower area of the
Display screen.
Vol(up)/Vol(down)
Increases or decreases the volume of the speaker.
Depth
After determining the centerline of the utility, set the blade
of the receiver on the ground, press and hold this pad to
get the depth to the center of the target.
TW-8800 RECEIVER
The receiver includes
the control keys and
a large
display screen.
Controls
Tracing
After locating the point(s) where the signal strength
was the highest, return to that spot and start tracing
your utility. This is where the LEFT/RIGHT indicator is very
helpful. Swing the Receiver from left to right and listen
for the change of tone. When the target is to the RIGHT
of the receiver, the signal is pulsed tone. As the receiver
gets closer to the target, the pitch gets higher. When
the target is to the LEFT of the receiver, the signal is a
continuous tone. As the receiver gets close to the tar-
get, the pitch also becomes higher. When the receiver
is over the target, OVER TARGET is showed on the dis-
play screen, and the tone is at its highest peak sound.
Depth Measuring
When an OVER TARGET response is displayed, position
the blade of the receiver directly over the utility. Place
the tip on the ground, hold the receiver steady,
and press and hold the DEPTH pad. Depth will be measured to the center of the utility.
OPERATING INSTRUCTIONS
11
7
TW-8800 RECEIVER
Frequency Modes
The frequency at which the receiver is operating.
<< Left/Over Target>/Right>>
Indicates where the receiver is in relation to utility.
Numeric Display
Serves a dual function:
•Relative signal strength of the transmitted signal (%
shown). Responds in conjunction with the bar graph.
•Depth to the center of the target (when DEPTH pad is
pressed - IN or CM shown)
Light
Indicates the display is lit (activated by pressing LIGHT pad).
Bar Graph
Serves three purposes:
•Responds in conjunction with signal strength.
•Visual indicator for battery test (when BAT pad is pressed).
•Volume loudness indicator (when VOL(up)/VOL(down)
is pressed.
Replace Batteries
When the receiver batteries fall below a nominal level,
REPLACE BATTERIES will be displayed.
No Signal
When no signal is received by the receiver, NO SIGNAL
will display. This response may be due to the transmitter
not being turned on, or the transmitter and receiver not
be set at the same frequency.
Display
8.2 kHz
A very versatile frequency. Can be used both conductively
and inductively. Can be used on continuous utilities – wire
or pipe. The signal has a better chance of not inducing
onto nearby utilities. This frequency may work better if the
utility is grounded.
820 Hz
This frequency is mainly used on grounded wires or cables.
It can give the longest trace distance of the three active
modes.
In the passive mode, set up a dened search pattern.
The pattern should include both north/south and east/
movement. Even though a signal may be encountered,
be sure to scan the entire area.
In the active mode, setup the transmitter either inductively or conductively.
Inductive
Be aware of air coupling, the transmitted signal travelling
to the receiver via the air, not the utility.
Conductive
Connect the ground plate/ground rod assembly to the transmitter. Connect the red lead to the non energized utility.
Connect the black lead to the ground rod/ground plate.
Place the plate/rod at a 90-degree angle in reference to the
utility. Be sure not to place the wires over any other utility.
After the transmitter is setup, move away from the point of
connection (or Induction) about 25 feet (8 meters). Sweep
a circle around the point of connection. Initially, disregard
the LEFT/RIGHT indicator and rely on the signal strength
readout. Make note of the high readings. These are areas
that need to be traced/examined in more detail.
OPERATING INSTRUCTIONS
10
INITIAL SCAN
WARNING: Do not handle output leads unless power is off.
ELECTRIC SHOCK HAZARD: Servicing to be performed by
qualied personnel only.
WARNING: Do not connect output leads to a live (ener-
gized) utility. Please prevent shock hazard and equipment damage.
8
ACCESSORIES
The coupling clamp is useful when the utility is exposed,
and a direct connection is not possible. It is plugged into
the same plug-in socket as the ground-plate/ground-rod
assembly. The coupling clamp only operates at the 82
kHz frequency. The coupling clamp will t around utilities
that are 3-¼ inches in diameter or smaller. The length of
the cable is approximately 10 feet.
Coupling Clamp
Fisher Research Laboratory has a variety of headsets
available.
•Ultra-quiet deluxe Fisher Phones. High quality sound while
reducing the outside noise.
•Standard Stereo Headphones
•Single Earpiece Headset. Enables the operator to ef-
fectively listen to the TW-8800 and remain aware of noise
in close proximity.
Headsets
This represents a jumper
Coupling Clamp Applications Diagram
A. The coupling clamp is for all
tracing applications with conduc-
tors exposed; exception, an
open
circuit at line’s termination.
B. A ground must be provided
for the proper current ow when
the coupling clamp is used at a
termination.
C. The coupling clamp must be
used betwe en th e gro undin g
and where the line goes underground.
D. Trace signal will return to ground
when incorrectly coupled.
E. Signal will be transmitted in both
directions when connect
ing is
midway in a long conductor.
F. Drop lines or laterals divide the
signal strength in half at each
junction.
9
OPERATING INSTRUCTIONS
The following instructions are designed for safe and effective
methods of line tracing and utility avoidance. Some of the steps
may not be applicable in all situations. The underlying guideline
is that operator safety must be maintained at all times. Use of
safety equipment, extra personnel, and up to date as-built plans
should be considered when necessary.
The TW-8800 gives the operator many tools in one easy to use
package. The following information can serve as guidelines to
assist the operator in using the TW-8800.
METHOD OF LOCATING
(The passive modes have no visual readout on the display.
Increasing the volume will give both an audio and a tactile
response.)
50 Hz/60 Hz (Power) Mode
Ideal for scanning an area to locate energized electrical
cables. Caution: Lower power may not give a clear, strong
response.
Radio Mode
Another scanning mode. Some telecommunications will
give a response in this mode.
82 kHZ
A good easy to use frequency. This frequency can be used
conductively, inductively, or with the coupling clamp.
Ideal situations include utilities that are noncontinuous,
poor conductors, not grounded, or where a direct con-
nection is not available. Examples of these would include
water mains with gaskets at the joints, telecommunication
cables where a direct connection is not available, and
wire in conduit that is non-continuous through out. High
frequencies have a tendency to induce signal onto other
utilities if nearby
Passive Mode
Active Mode
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