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CONTENTS PAGE NO.
A. General Description . . . . . . . . . . . . . . . . . . . . . . . .1
B. Major Components And Accessories . . . . . . . . . .1
1. Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2. Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3. Direct-Connection Cable (DCC) . . . . . . . . . . . . . .5
4. Ground Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
5. GC-2 Cable Clamp . . . . . . . . . . . . . . . . . . . . . . .5
6. Headphones . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
7. Carrying Bag . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
C. Modes Of Operation . . . . . . . . . . . . . . . . . . . . . . . .6
D. Operating Procedures . . . . . . . . . . . . . . . . . . . . . . .7
1. Energizing a Line to be Traced . . . . . . . . . . . . . .7
a) Inductive Energizing . . . . . . . . . . . . . . . . . . . .7
b) Conductive Energizing . . . . . . . . . . . . . . . . . . .9
2. Tracing an Energized Line . . . . . . . . . . . . . . . . .11
a) Peak Detection Method . . . . . . . . . . . . . . . . .11
b) Null Detection Method . . . . . . . . . . . . . . . . . .14
c) Determining Depth of a Line . . . . . . . . . . . . . .15
3. Finding Lines of Completely
Unknown Location . . . . . . . . . . . . . . . . . . . . . . .17
4. Locating Hidden Valve Caps
and Manholes . . . . . . . . . . . . . . . . . . . . . . . . . . .18
E. Miscellaneous Notes and Suggestions . . . . . . . .20
F. Instrument Maintenance . . . . . . . . . . . . . . . . . . . .20
1. Battery Replacement . . . . . . . . . . . . . . . . . . . . .20
2. Mechanical Care . . . . . . . . . . . . . . . . . . . . . . . . .21
3. Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . .22
G. Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
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A. General Description:
The Goldak Model 902 is a hand-held electronic pipe and cable
locator, designed according to the classic “split-box” concept. Like
its predecessors in the Model TR series, the Model 902 is used to
trace underground conductive networks such as water and gas
mains, telephone, cable TV and electric power cables, and any continuously conductive pipe or cable. Also, as with traditional “splitbox” locators, the Model 902 may be used to electronically determine the depth of buried lines, by employing simple operating techniques.
However, the Model 902 also incorporates features that are not
found in traditional locators. Designed with patented SI (super-inductive) technology, the Model 902 packs superior performance into a
convenient, hand-held package that is significantly smaller than
other two-box locators. Durability of the Model 902 is insured by
solid construction in a tough, Xenoy housing. Also, to enhance locating convenience, sub-surface metallic structures, including valve
caps, risers and manhole covers, can be found easily during tracing
by pressing a single push-button switch.
B. Major Components and Accessories:
1. Transmitter.
The transmitter generates a signal which is to be used to
“energize” the conductive line to be located. When a line is
energized, it radiates the generated signal in a pattern which
corresponds to the direction of the line, and which may be used
not only to trace the line but also to determine its depth. The
signal may be transferred to the line by one of two methods:
inductively or conductively. Inductive transferrance does not
require the line to be electrically exposed. Conductive transferrance requires that the transmitter be connected physically via
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cable to the line to be traced. Section D of this manual,
“Operating Procedures,” explains these transmission methods in greater detail. A detailed explanation of the transmitter
features and controls follows here (refer to Fig. 1):
a) The POWER Switch. This booted push-button switch
controls the power state of the transmitter. Depressing
this switch so that the adjacent “BATT” light illuminates
“turns on” the transmitter, causing it to generate a signal.
Depressing the switch again will deactivate the transmitter.
b) The BATT Indicator. This LED is lit when the transmitter is
activated and the condition of the battery source is good.
If this LED does not illuminate when the POWER switch is
pressed, or it becomes unlit during operation, the batteries need to be replaced.
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c) The PULSE Switch. This switch controls whether the
signal generated by the transmitter is continuous or
pulsed at a frequency of 5 to 10 times per second.
Pulsing the signal allows it to be easily identified and also
conserves the transmitter's batteries. The transmitter is in
“pulse mode” when the BATT indicator is flashing.
d) The OUTPUT LEVEL Switch. This push-button controls
the intensity of the signal that is generated by the transmitter. Depressing this button so that the “HI” indicator is
lit transmits the maximum amount of signal for any given
signal transfer method. When the “HI” indicator is unlit,
the signal output is reduced.
e) The HI Indicator. As explained above, this LED indicates
the level of signal that is presently being transmitted.
f) The DIRECT OUTPUT Jack. Inserting the plug of the
directconnection cable (hereafter referred to as the
“DCC”) into this jack switches the transmitter into “conductive” mode. In this mode, a line may be energized
directly by physically connecting the red clip of the DCC
to an exposed part of the line.
2. Receiver.
The receiver is used to detect the signal generated by the
transmitter, and therefore to trace the conductive line that the
transmitter is energizing. While locating a line, the operator
may use the receiver in either of two tracing modes: peak
and null. When using peak mode, the operator searches for
a maximum signal; this is the most sensitive mode. In null
mode, the operator looks for places where the signal vanishes. A single pushbutton sets the receiver in an auxiliary
detection mode (locate mass) which allows the operator to
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conveniently find buried metallic masses, such as valve caps
or manhole covers. Section D of this manual, “Operating
Procedures,” contains more details about these locating
methods and others. Specific features and controls found on
the 902 receiver panel are described here (refer to Fig. 2):
a) The POWER Switch. This push-button switch activates
and deactivates the receiver. The receiver is activated
(“on”) when the POWER switch is depressed so that the
“BATT” light above this switch illuminates. Depressing the
switch again will turn the receiver “off”.
b) The BATT Indicator. When the condition of the batteries in
the receiver is good, this LED shines when the receiver is
activated. If this indicator does not shine when the
POWER switch is pressed, or it stops shining during
operation, then the batteries need to be replaced.
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c) The SENSITIVITY Switch. Using this button will toggle the
sensitivity of the receiver between a low and a high state.
That is, this switch controls the receiver’s overall sensitivity to the signal produced by the 902 transmitter. The LED
indicator above this switch monitors what the present
sensitivity mode of the receiver is. (NOTE: This switch
does NOT control the sensitivity of the receiver while in
“locate mass” mode.)
d) The HI Indicator. This LED indicates the present sensitivity
of the 902 receiver when in normal tracing mode. The
indicator will be lit to correspond to a state of high sensitivity. Likewise, the LED will be darkened in the low
sensitivity mode.
e) The LOCATE MASS Switch and Indicator. Pressing this
switch so that the LED indicator directly above it illuminates changes the 902 receiver from a line tracer to a
metallic mass locator. Examples of buried masses that the
receiver is able to find in this mode are valve caps and
manhole covers. Using the instrument in this mode
disables normal receiving functions.
f) The SIGNAL LEVEL Control. This knob is the most impor-
tant control on the 902 receiver from an operating standpoint. While in tracing mode, use this knob to gradually
adjust the sensitivity of the receiver to the transmitted
signal. When tracing in “peak” mode, use this control to
set the point of maximum signal on the response meter;
in “null” mode, use it to adjust the width of the signal null.
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g) The Light Bar Meter. This solid-state LED bar meter pro-
vides a visual indication of the level of signal presently
being received. As described above, the response meter
will indicate both peaks and vanishing points in the signal
surrounding the line being traced.
h) Speaker. A water-resistant, small but powerful mylar
speaker delivers a strong audio output corresponding to
the signal received by the 902. In tracing mode, the sound
will track the LED meter response; however, in masslocating mode, the speaker delivers a continuous tone,
the frequency of which will rise when the receiver is
brought near to a metallic mass.
i) Headphones Jack. All sound normally supplied by the
speaker will be channelled to headphones when the
headphone plug is inserted here.
j) 45° Level Guage. When making a determination of line
depth, the operator will often find this small level helpful.
Oriented at a 45° angle with respect to the antenna, the
bubble in the level will center itself when the antenna is
positioned at 45° compared to level ground. See section
D of this manual for more information on determining line
depth.
3. Direct-Connection Cable (DCC).
Included with every Model 902 instrument, this accessory
consists of a phone jack wired to two separate copper
clamps. Use this cable to inject the transmitter signal directly
into a specific line, thus conductively energizing it. To
accomplish this, connect the red clamp to the exposed line,
and optionally attach the black lead to some ground if
increased tracing distance is desired.
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4. Ground Rod.
This U-shaped rod, also included with every 902, simply
gives the operator a means of establishing a solid ground for
conductive tracing. To use the ground rod, push it into some
soil, and clip the black lead of the DCC to it.
5. GC-2 Cable Clamp.
This accessory is useful when the operator wishes to energize a specific line, but there is no electrically exposed area
to make a conductive hook up. If the GC-2 is clamped
around a specific line, it will inductively energize the line with
a focused signal. The line will become considerably more
energized than surrounding lines, and therefore easily traceable. The Model GC-2 clamp is sold separately.
6. Headphones are also sold separately from the Model 902.
Any set of headphones may be used with the Model 902
Locator, provided it has a standard quarter-inch plug. We
recommend a comfortable “walkman” style of headphones,
which comes with a quarter-inch plug adapter.
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7. Carrying Bag.
There are two kinds of carrying bag available for the 902
locator, both constructed from rugged nylon canvas. The
smaller bag comes with the instrument originally and contains only enough room to carry the instrument and its basic
set of accessories. The larger bag has additional pouches
specifically tailored to house the GC-2 cable clamp, a set of
headphones, and other miscellaneous items. The larger bag
is sold separately.
C. Modes of Operation:
1. Transmission Modes.
There are two modes of signal transmission for the Model
902 Pipe and Cable Locator: inductive and conductive. Two
discrete output levels may be selected for either mode, and
the operator may choose to pulse the signal in either mode
of transmission for easier identification.
a) Inductive Transmission. In inductive mode, the 902 trans-
mitter produces a radio signal capable of penetrating air,
ground, and other media in order to energize a nearby
conductive line. Having been effected by the transmitted
signal, the line then conducts the signal along its path.
The signal pattern surrounding the line corresponds to the
path of the line itself. Therefore, the operator may use the
902 receiver to trace the direction of the line and to
determine its depth from the signal pattern surrounding it.
Although energizing a line inductively can be convenient
and sometimes necessary, this method typically is less
precise than conductive transmission in its ability to
isolate a desired line.
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b) Conductive Transmission. To activate this mode of trans-
mission, the operator inserts the plug of the direct-connection cable into the DIRECT OUTPUT jack on the transmitter control panel. Connecting the clip of the DCC
directly to some exposed part of the line will channel the
radio signal into the line through the cable. The line then
conducts the signal exactly as it does if it is inductively
energized, and the receiver can trace the line the same
as well. However, in this mode, energizing is much more
precise as well as more efficient. Therefore, one can generally expect longer and more reliable traces when using
conductive transmission. This is the preferred method of
transmission, and should be used in most cases when a
portion of the line to be traced is exposed.
2. Receiving Modes.
As for the transmitter, there are two general modes of location for the 902 receiver: line tracing and mass locating.
For line tracing, the operator may choose between two
discrete levels of receiver sensitivity.
a) Line Tracing. This mode is used exclusively to detect the
signal generated by the 902 transmitter, and therefore to
locate lines which the transmitter is energizing. When
tracing, one may choose to use either of two methods:
peak or null. The operator selects the method solely by
how he positions the receiver with respect to the line
being traced. Peak method is selected by holding the
receiver so that the plane of the face of the receiver is
perpendicular
to the surface above the line being traced.
Holding the receiver so that the face lies parallel
to this
surface causes the signal to vanish when the energized
line is located; this is null method. In line tracing mode,
the operator may ascertain line depth by using simple
techniques.
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b) Mass Locating. At any time when the operator is using the
902 receiver for line tracing, he may choose to activate
mass locating mode. In this mode, the receiver sounds a
continuous tone and indicates detection of a metallic
mass with a notable shift in the frequency of the audio
tone. The frequency heard will rise when a conductive
mass is detected, and lower when a strictly ferrous mass
is detected.
3. Two-Box Modes.
The transmitter and receiver may be configured together to
enable location of "unknown" lines, lines which have no
known point at which to energize them. One method of finding unknown lines involves having two operators, each holding one of the locator boxes and moving together in the area
that a line is suspected to be found.
D. Operating Procedures:
1. Energizing a Line to be Traced.
The Model 902 is an "active" locator. This means that the
902 receiver is designed to detect lines that have been energized by the signal generated from the 902 transmitter.
Therefore, the operator must prepare to trace a specific line
by first energizing it. Following are the methods for energizing lines.
a) Inductive Energizing
Using this method, the operator can energize the desired
line without having to make any physical contact with it.
Placed correctly upon the ground or pavement below
which the line to be traced lies, the transmitter radiates its
radio-frequency signal to the line (Fig. 4). Once effected
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by the radiated signal, the metallic line behaves like a
large antenna, retransmitting the signal through the
ground and air in a pattern that corresponds to its path.
The line carries the signal on its path for several hundred
yards, depending on its depth, the mineralization and
conductivity of the ground, and the transmitter power setting. To use inductive energizing, follow these steps:
i) Make sure that
the DCC is
removed from the
direct-output jack
on the transmitter.
If it is not, the
transmitter is in
conductive mode
and will not radiate
a signal through
the air.
ii) Turn on the transmitter. You have activated the transmit-
ter if the green BATT light is glowing. If you have
depressed the POWER button and the light does not
glow, you probably need to change the batteries.
iii) Select a power setting on the control panel of the
transmitter. Using the OUTPUT LEVEL switch, select
either low or high output power. High output is indicated when the HI light is glowing. At this time, you may
also want to set the PULSE switch. If the BATT light
blinks, the energizing signal will pulse as well. Such a
signal is often easier to identify while tracing.
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iv) Place the transmitter on the ground at a known location
directly above the line that you want to energize. As
depicted in Figure 5, it is important to place the transmitter vertically and in the direction of the underground line.
Since the transmitter radiates a signal directionally, this
orientation over the line will optimize the signal transfer
into the line. With improper placement or orientation, it is
possible to cause little or none of the signal from the
transmitter to actually energize the line.
NOTE: It should be known that when placed over a line to ener-
gize it, the transmitter radiates signals from the sides and
top as well as from the bottom. Signals radiated through
the bottom are used to energize the line. Those coming
from the sides and top travel a short distance through the
air and are attenuated.
If the transmitter is aligned perfectly with the underground
line, the signals emerging from the sides will travel along
the path of the line. This can cause some confusion when
working close to the transmitter. To avoid such confusion,
offset the transmitter 10° or 15° from the general direction
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of the line (Figure 6). The signal entering the line will
still be nearly optimized, and line tracing near the transmitter box will be much truer.
b) Conductive Energizing
Unlike the inductive method, this energizing method
requires the line to be exposed so that a direct connection
can be made to it. However, conductive energizing presents significant advantages over inductive energizing, and
is therefore the preferred method. Since the signal enters
the line directly through the DCC, unwanted air signals are
minimized. Using a ground with the DCC will maximize
the energizing efficiency, so that tracing distance can
increase dramatically. More details concerning the application of the DCC for direct hookup follow here and are
depicted in Figure 7:
i) Insert the plug of the DCC into the DIRECT OUTPUT
jack on the control panel of the transmitter. This will
automatically deactivate the inductive antenna.
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ii) Clip the red clamp on the DCC to an exposed portion
of the line that you wish to trace. Make sure that you
make good electrical contact with the line.
iii) If you choose to use the ground rod, insert it into the
ground several feet away from the line. Clip the black
clamp of the DCC to the ground rod, again insuring
sound electrical contact. NOTE: Grounding the DCC
while using the transmitter conductively is recommended, since this will dramatically increase the strength of
the signal on the line.
iv) If you choose not to use a ground, stretch out the
black cable and let it lay freely on the ground. Although
the magnitude of the signal carried on the line will be
small, it usually will be strong enough for short traces
very close to the transmitter. Working without a ground
is often helpful when tracing indoors or in other confined areas.
CAUTION:
Do not connect the red and black clips together when
using the DCC. Although short-circuiting the output
leads will not result in immediate damage to the transmitter, it will quickly drain your batteries and cause the
internal circuitry to heat up. If such internal heating is
allowed to occur for an extended period of time, eventual damage may occur.
2. Tracing an Energized Line.
As the energized line carries the signal from the transmitter, a
cylindrical pattern of energy forms around the line (Figure 8).
In general, the strength of the signal is strongest at the center of this cylinder and gradually decreases away from the
center. The 902 receiver employs a directional antenna, so
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that it can detect the signal in different response modes
depending on how it is positioned. By manipulating the
receiver over the line and properly interpreting the results,
an operator can perform several locating tasks with high
accuracy.
a) Peak Detection Method
Tracing a line by finding maximum points of signal, or
“peaks”, is the most intuitive method of tracing, although
not the most accurate. Both location and direction of a
line can be determined simply by positioning the 902
receiver so that it indicates a maximum relative response.
The following steps illustrate how this is accomplished.
i) After having energized a pipe or cable, turn on the
receiver. At first, set the sensitivity to low (HI light off);
also, make sure that the LOCATE MASS feature is
deactivated (LOCATE MASS light off).
ii) If you are using inductive energizing, walk down the
line 20 or 30 feet, moving further out of range of air
signals coming from the transmitter. If you are using
conductive energizing, you may begin tracing close to
the transmitter.
iii) Hold the receiver vertical and in the approximate direc-
tion of the line as shown in Figure 8. Adjust the
SIGNAL LEVEL control so that the receiver responds
to the signal from the line at around 3/4 scale.
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iv) Now move the receiver back and forth, causing the meter
and sound response to increase and decrease and "peak"
over the line. Continue peaking over the line as you walk
in the direction of the
line; the line will be
directly below where
the signal response is
maximum as you walk.
v) As you distance yourself
from the point at which
the transmitter is
energizing the line, the
signal intensity will
continue to diminish.
Thus, the receiver
response will decrease
as well. To gradually
increase the relative
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sensitivity of the receiver, turn the SIGNAL LEVEL
control in the clockwise direction, keeping the
response between 1/4 to around 3/4 scale. When the
signal from the line has faded so that it is no longer
detectible, push the SENSITIVITY button so that the HI
light glows. You may then continue tracing as before.
vi) At any time while tracing, you may determine the direc-
tion and depth of the line. To determine the direction,
rotate the receiver left and right as shown in Figure 9.
Notice that rotating the receiver will cause a peak
response as well. When the response is maximum, the
receiver box is parallel to the direction of the line. For
information on determining line depth, see part (c) of
this section.
vii) If, while tracing, the signal suddenly vanishes along the
direction you are moving, then the line either ends at
that point or it has turned to the right or the left. Figure
10 depicts a simple way to determine if the line has
turned. Walk back up the line about four feet and then
walk in a circle either right or left. Keep the side of the
receiver box pointed toward the center of the circle. If
a lateral turn exists, the receiver will peak over the line,
giving the direction of the turn. If the line simply ends,
then no other strong peaks will be detected.
viii) If, during tracing, the signal gradually fades and the
receiver is set to its highest sensitivity, then you may
continue tracing by bringing the transmitter closer and
reenergizing the line at a point you have already
located. Usually, you would use inductive energizing
when moving the transmitter closer, but connecting to
a nearby part of the line that is exposed is preferred.
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b) Null Detection Method
Also called “centering,” tracing a line by finding points
where the signal vanishes (“nulls”) is an alternate method
to peaking. Because the receiver relies on a directional
antenna, positioning it so that the front panel perfectly
faces the line will cause it to detect no signal. Using nulls
over the line, the operator can ascertain the precise location of a line below the surface, as well as determine its
depth.
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i) Turn on the receiver and prepare for tracing as
described in steps (i) and (ii) of section (a), Peak
Detection Method.
ii) Hold the receiver flat with respect to the surface above
the line (Figure 11a). Set the SIGNAL LEVEL control
between half and full scale. This will insure that the
signal is detected strongly when the receiver is not
directly over the line.
iii) Now slowly move the receiver back and forth over the
line. The response will be full everywhere in the vicinity
of the line, except directly above it. At this point the
response will vanish sharply (Figure 11b). As you walk
along the line, it will always be located directly below
the point where the signal disappears.
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iv) As with the peak method, the signal on the line will
gradually diminish as you continue to trace. Notice that
as you trace further away from the transmitter, the null
becomes wider and less sharp. To sharpen the null,
continue to advance the SIGNAL LEVEL control. If this
control has been set all the way clockwise and you
wish to sharpen the null more, press the SENSITIVITY
button so that the HI light glows, and continue tracing
as before.
v) If the null suddenly disappears, this could indicate that
the line has ended or turned. To determine if the line
has turned, you may follow the procedure described in
section (a)(vii) above, using nulls instead of peaks over
the line.
vi) Please note that the null method will not indicate the
direction of the line at a single point. As long as the
receiver is held flat to the surface, it will indicate a null
over the line regardless of how the box is rotated.
vii) If you have traced beyond a detectible range, you may
continue your trace by re-energizing the line at a point
closer to where you are locating.
c) Determining Depth of a Line
Using the null detection method described above, the
operator can make a surface measurement and determine
the depth of an energized line. The procedure requires
two null points to be marked.
i) Locate the point at which you want to measure the
depth of the line.
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ii) Using the null method, pinpoint the spot on the surface
directly above the line and mark it.
iii) Turn the receiver to the 45° position. Use the level on
the face of the receiver marked “45° LEVEL GUAGE”
to set this position. The receiver will be properly positioned when the bubble in the level is directly in the
center.
iv) Now move the receiver away from the first null mark at
a right angle from the direction of the line (Figure 12 &
13). You will locate a null as you move the receiver
horizontally. Hold the receiver so that the bottom edge
of the bottom of the box sets on the ground when finding this 45° null to obtain accurate results.
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v) When you have obtained a sharp 45° null, mark the
ground there. Note that for accurate results, you should
mark the ground directly below the top edge of the
bottom of the receiver, in order to account for the
physical dimensions of the receiver box.
vi) Measure the distance between the two null marks
(Figure 9). By triangulation, this surface distance will
be the same as the depth to the center of the line. For
excavation or trenching purposes, this means that the
actual top of the pipe or conduit will be shallower than
the measured depth by half of the pipe’s diameter. For
example, for a 12-inch diameter pipe, the actual depth
to the top of the pipe will be 6 inches less than the
measured depth.
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vii) It is good practice to repeat the depth measurement on
both sides of the line. The symmetry of the signal pattern around the line can often be effected by ground
conditions, laterals and other service lines. If the measurement is the same on both sides, then the depth has
been accurately found. If not, then the more accurate
measurement will be that which renders the best
defined nulls.
3. Finding Lines of Completely Unknown Location.
It is possible to use the receiver and the transmitter in conjunction to survey areas for unknown lines. This procedure
involves carrying both the transmitter and receiver together
at a fixed distance and orientation, and setting the receiver
controls so that the receiver is just out of range to detect air
signals coming from the transmitter. This is a two-person
operation.
a) One person carries the activated transmitter, and the
other carries and controls the receiver.
b) Each person must keep the boxes in line with each other
and at a constant distance from each other as shown in
Figure 14. A horizontal separation of 30 or 40 feet is recommended.
c) Set the transmitter for low inductive output, and set the
receiver to low sensitivity, advancing the SIGNAL LEVEL
control so that the response is just below the threshold of
detecting the air signal from the transmitter.
d) Each person should now walk parallel to each other,
making sure that the 902 boxes remain in line with each
other and at a constant distance from each other. If the
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two cross over a line that is at a right angle to the direction they are walking, the transmitter will energize the line
while the receiver detects the newly energized line.
e) At this time, the person carrying the transmitter should
move the transmitter back and forth across the line, causing a maximum response at the receiver. Thus the transmitter may be centered over the line. If the transmitter is
placed on this spot, it will continue to energize inductively
the newly found line. Using the receiver, trace the line and
determine depth as you normally would.
f) NOTE: This method of finding an unknown line works only
if the operators cross the line at a roughly right angle.
Therefore, the operators may choose to sweep the area in
question in several directions, to assure that they cross all
unknown lines.
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4. Locating Hidden Valve Caps and Manholes.
The 902 receiver incorporates a feature that makes locating
masses of metal buried below the surface simple and convenient. Activating the LOCATE MASS button reconfigures
the receiver antenna, making it sensitive to nearby metallic
masses, such as manholes and valve caps. A continuous
tone emerges from the receiver which changes frequency
when brought near a metallic mass. Details on using this
feature follow here (see Figure 15).
a) At any time while you are tracing a line, you may press the
LOCATE MASS button. Once set to locate masses, the
receiver outputs a continuous tone.
b) Move with the receiver held flat to the surface beneath
which you a searching for a mass. In this mode, the
receiver is only sensitive to about 18 to 24 inches, so you
must search with the receiver held close to the surface.
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c) When the receiver passes over a mass, the frequency will
increase. The rise in frequency depends on the proximity
of the buried mass. A sharp increase indicates a shallow
mass, probably no more than 6 inches deep. A slight
increase indicates a depth probably greater than a foot.
In either case, the center of the mass will be found below
the point of highest frequency.
d) When locating a large mass, such as a manhole, it may be
helpful to find the edges of the mass rather than the center. To locate the edges, scan the area around the mass,
marking locations where a sharp frequency rise occurs. If
you mark 3 or 4 evenly spaced locations around the
perimeter you may use these to trace the outline of the
manhole. Also, these markings will help you more accurately visualize the center of the manhole.
e) The SIGNAL LEVEL control may be adjusted in this mode
to provide a visual response on the light bar meter.
Generally, an increase in the light bar meter reading will
correspond to a frequency rise due to the presence of a
mass.
f) NOTE: The SENSITIVITY button has no function in mass-
locating mode, and may be left on either setting.
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E. Miscellaneous Notes and Suggestions:
1. Energizing Lines.
a) When energizing a line inductively, avoid setting the
transmitter directly on the line or within a foot of large
masses of metal. The transmitter will continue to function under these conditions, but the energizing efficiency might be reduced considerably.
b) For long tracing runs, periodically bring the transmitter
closer to the area you are working and re-energize the
line. This will insure a solid tracing signal.
c) Signals entering a line at one point may be transferred
to another line through a common point. Erroneous
conclusions may result. This kind of transfer may occur,
for instance, when energizing a gas service that feeds
into a water heater. At the heater the gas service may
be electrically common with the incoming water pipe;
the water pipe might carry the signal as well, thereby
leading the operator to false conclusions while tracing.
The operator should be aware of the possibility for
false signals.
2. Tracing Lines.
a) Remember to be aware of airborne signals when work-
ing close to the transmitter. Either offset the transmitter
over the line as described, or energize the line from a
point further from where you are working.
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F. Instrument Maintenance:
1. Battery Replacement.
Both parts of the Model 902 Locator are powered by four
alkaline “C” size batteries each (Eveready # E-93). When
the transmitter and receiver are on, the power supply of
each is constantly monitored by its own BATT light. When
the BATT light on an instrument no longer glows when
the instrument is on, the batteries need to be changed
for that instrument. To change the batteries of either
instrument:
a) Lay the instrument on a table with the front panel fac-
ing upward.
b) Using a regular size phillips-head screwdriver, remove
the four screws at the corners of the face panel.
c) Holding the face panel with your fingers, flip the instru-
ment over onto your lap or onto the table and lift the
blue shell off of the face panel.
d) Remove the two phillips-head screws that hold the
battery strap into place and remove to battery strap.
(At this time, be very careful not to change any of the
circuit board controls unless you are a trained technician.)
e) Remove the old "C" cells and replace them, making
sure to follow the polarity instructions on the bottom of
the battery well.
f) Turn on the instrument briefly to confirm that the BATT
light glows. If it does not, check to make sure you
inserted the batteries correctly.
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g) Replace and screw down the battery strap.
h) Carefully drop the shell over the face panel and make
sure that the handle on the shell is right side up. Hold
the face panel in with your fingers, flip over the instrument, and replace the four phillips-head screws.
2. Mechanical Care.
a) Although the Model 902 Locator has been designed to
be rugged and can withstand a reasonable amount of
shock, it should be handled with care. Heavy shock
can cause minor changes in the radio-frequency tuning, which is undesirable although it will not render the
instrument useless. In general, care for the Model 902
as you might care for a portable AM/FM radio.
b) We do not recommend the addition of large metallic
objects to the shells or faces of the instrument. Both
the transmitter and receiver are tuned at the factory to
compensate for the batteries, circuit boards and other
metal in the instruments. Adding metal will detune the
instrument and should not be done unless a trained
technician is present to retune the instrument.
3. Troubleshooting.
If problems arise when attempting to operate the Model
902, the operator may perform some simple troubleshooting with little technical knowledge.
a) If the BATT light does not glow when the receiver or
transmitter is activated, it may simply mean that the
batteries need to be replaced. In this case, you may
verify that the transmitter has been activated by pressing the OUTPUT LEVEL button. If the HI light comes on,
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then the transmitter is probably working properly, but
the batteries are low. You may verify activation of the
receiver by pressing either of the SENSITIVITY or
LOCATE MASS buttons. If the status light accompanying the button glows, then the receiver is probably
operating on low batteries.
b) Cold weather can effect the performance of the alkaline
batteries in either the receiver or the transmitter. At
freezing (32°F or 0°C), typical alkaline battery capacity
can be cut by 50%. Although the transmitter and
receiver will still work despite this decline in capacity,
overall performance will decrease. One way to solve
this problem is to install cold-weather batteries.
Eveready produces such a line of batteries called
“Litheon” batteries.
c) If new batteries have been installed and the BATT light
still does not come on, check to be sure that the batteries have been installed with the correct polarity.
CAUTION: If all the batteries are in reverse polarity, the
internal circuitry may become damaged. Therefore, if
the light does not come on, immediately turn off the
instrument.
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G. Servicing:
For more technical information about the Model 902, or if
servicing and repairs are necessary, contact the factory at the
following address:
Goldak, Inc.
15835 Monte Street, Unit 104
Sylmar, CA 91342
818-367-0149
fax: 818-833-7694
email: [email protected]
website: www.goldak.com
We will inform you of any local repair stations in your area,
or advise you to ship the instrument directly to the factory.
If you ship product, we suggest you:
a) Pack the instrument carefully and securely.
b) Include any accessory items normally used with the
instrument.
c) Include a note with the instrument stating the nature of the
problem(s) you have encountered in using the instrument.
d) Include a contact name, telephone number and fax number.
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