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com
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SOLID STATE

PIPE & CABLE LOCATOR

I

I NILSSON ELECTRICAL L A B O R A T O R Y , INC.

SPECIALISTS IN ELECTRONIC AND ELECTRICAL MEASUREMENTS

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NILSSON ELECTRICAL LABORATORY, INC. PIPE & CABLE LOCATOR MODEL 715
CONTENTS
Section 1 PHYSICAL CONSTRUCTION
Page

2-3 Section 6 OPERATING NOTES 8-9

I
1.1 Transmitter
1.2 Receiver 6.1 Distance and depth
1.3 Optional equipment 6.2 Cable opens and grounds
6.3 River crossings
Section 2 THEORY OF OPERATION 6.4 Bends and stub ends
4 6.5 Branch taps and foreign contacts
Section 3 OPERATING INSTRUCTIONS 6.6 Building electric circuits and piping
4-5
Section 4 ANTENNA POSITIONS Section 7 BATTERIES AND 10 ~
4.1 Maximum signal 5-6 REPLACEMENT
4.2 Minimum or null position I

4.3 Depth determination Section 8 REPLACEABLE PARTS AND 10 ‘

REPAIRS
I
I
Section 5 ESTABLISHING SIGNAL
b-/ I
CURRENT CIRCUIT

***
-, The Model 715 contains no movirw !
parts, such as vibrator contacts or relays, t;
wear out and require adjustment. Full advan-
tage is taken of modern solid state technology
to provide efficient transfer of a signal current
into a ground circuit and accurate tracing of
the signal in the substructure being investi-
gated.

PARTICULAR INSTRUMENT REQUIREMENTS Page 1

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/
Section 1
PHYSICAL CONSTRUCTION
The physical design emphasizes versatility in the A low battery warning lamp is provided. This is
use of accessories to best suit the needs of the NOT a pilot light. It will ONLY light when the
problem at hand. The locator is light weight, rugged battery voltage is down to 9-10 volts, indicating the
and compact, intended for industrial use under need to replace or recharge the battery.
adverse field conditions. The entire unit is housed in a
deep drawn vinyl clad aluminum case, with storage 1.2 RECEIVER
space for accessories. The transmitter is mounted in The receiver, stored behind a clamp under the
the case with a panel containing all controls. The transmitter, is housed in a square phenolic tube. It
receiver, removed from its storage in the case, is contains input circuitry, on-off volume control, amp-
designed as a basic “handle” into which antenna and lifier, batteries and an output jack. It forms the
output accessories are plugged. handle for the flat coil antenna.
1.1 TRANSMITTER In operation the antenna is inserted into a jack
The transmitter is designed to operate from a 12 at the volume control end—and headphones or an
volt D.C. power source. It contains a circuit that output accessory is plugged into the jack at the
generates a distinctive A.C. signal. The pitch of the opposite end. The unit is now ready for use.
signal is variable by means of the “FREQUENCY” Whenever the headphones or other output device is
control. The signal is also periodically interrupted to unplugged, the batteries are automatically dis-
make the tone more distinctive. The rate of inter- connected, preventing accidental battery drain.
ruption is adjustable with the “RATE” control. The antenna coil is moulded in an epoxy
With the use of these two controls, the signal compound and mounted on a hinge joint rod. A
may be adjusted to be readily distinguished from any bubble level is moulded in which indicates both
background noise such as power line hum, traffic horizontal and 45 degree inclination.
noise, etc. The proper output impedance match is 600
Three output impedance ranges are provided, ohms. The headphones supplied are of 600 ohm
selected by the “IMPEDANCE” switch. This allows impedance. (Do not confuse impedance with the
the operator to select the best match of transmitter resistance of the phones. )
output circuit to the existing conditions.
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The aluminum plate under the volume control as OUTPUT METER

.4
well as the receiver name plate strip are connected to The output meter is housed in a small
the receiver ground. When holding the receiver in a metal case. It is a ruggedized sealed meter, properly
normal manner it assures body contact to receiver damped to visually display and follow the received
ground and prevents feedback howl when headphones signal. A jack in the case permits using the head-
are used. When working with gloves on and using phones at the same time, providing an audio-visual
headphones, it is recommended that some simple display for exacting work.
way, such as a bare wire through a finger of the glove, ANTENNA EXTENSION ROD
be used to establish finger contact with receiver The antenna and receiver combination pro-
ground. vides a “wand” 17 inches long. One extension rod
(supplied) extends this to 28 inches. Additional 11
inch extension rods may be purchased.
ANTENNA CABLE
1.3 OPTIONAL EQUIPMENT The antenna may also be coupled to the
The Model 715 locator consists of case, receiver by a cable. Thus an extra antenna may be
mounted transmitter, antenna, receiver, one exten- mounted on a truck and wired into the receiver in the
sion rod and 600 ohm headphone. The additional cab for riding surveys. When an area for close
options listed below are available. investigation is found, the receiver is disconnected
LOUD SPEAKER and another antenna added in the usual manner. I
The loud speaker is housed in a small metal Cables are supplied to order at length specified.
case containing a transformer and 2% inch speaker,
arranged to plug into the ouput jack in place of the MODEL 110 RECHARGEABLE 12 VOLT
headphones. The receiver amplifier has ample drive BATTERY PACK
for this and a loud clear signal is heard. A clip is Will outlast hundreds of 12 volt lantern
provided in the case cover for storage. batteries. Full description on page 10.
Page 3

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Section 2 Section 3
THEORY OF OPERATION OPERATING INSTRUCTIONS

The Model 715 operates on what is known as The “OUTPUT” binding posts of the transmitter should
the “conductive” principle. be connected to the conductor in one of the several ways
The transmitter generates a distinctive electrical described in Section 5.
Remove the receiver from the case and assemble with the
signal current. By proper application, the current is
antenna and headphones or other output accessory. Turn on
caused to flow in a loop circuit part of which is the
both units.
pipe or cable (hereafter called the conductor) being NOTE
invest igated. After the transmitter has been turned on, the
An electric current flowing in a conductor operator should not contact the output bind ing
generates a magnetic field around that conductor in a posts or wiring. A shock may be received which is
circular pattern. If an antenna coil is placed within not dangerous but may be annoying, especially in
that field, an electric current is induced in the the “H l“ position of the impedance switch.
antenna. This current can be amplified and heard in Listen to the signal and adjust the “FREQUENCY” and
headphones or loud speaker. “ R A T E ” controls for the most distinctive tone for the
The relative loudness of the signal, together with conditions.
Listen to the received signal some twenty feet away AT A
the position of the antenna coil, enables the operator
LOW VOLUME SETTING. Try the three positions of the
to determine with precision the course of the “IMPEDANCE” switch and select the one which gives the best
conductor and its depth below ground surface. signal.
An understanding of these principles, and ex- You are now ready to trace the path of the conductor.
perience in the use of this equipment, enables the Best receiver operation will occur with the volume set to the
operator to deduce many other factors, such as lowest level at which it can be heard comfortably. This will
location of branches, contacts with other metallic reduce the effect of background noise and make srmal I changes
structures, condition of insulating joints, location of in signal strength more easily detected.
opens and grounds, etc.

Page 4

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Section 4
ANTENNA POSITIONS

It is important that the operator gain a thorough

\
understanding of the relationship between the posi-
tion of the antenna, the strength of the signal
(
received, and the position of the conductor.
4.1 The /oudest (MAXIMUM POSITION) signs/ is
heard when the edge of the antenna disc points FIG. M

directly at the conductor and the disc is para//e/ with

NO SIGNAL WHEN AT RIGHT ANGLE TO CONDUCTOR
the conductor. (Figure 1A) The signal fades as the
disc moves away from this position. If the disc is
exactly at right ang/es to the conductor, no signal will
@
be heard.. ( Figure 1 B) (I7
4.2 Minimum signs/ wi// be heard (NULL POS IT I ON) / / / / / / / / / / / / / / / / / /
when the flat side of the disc faces the conductor and
is parallel with it. (Figure 2)
FIG. lB
A very critical position can be found where the Q

signal is inaudible. This position is very sharp, often

only a fraction of an inch wide, depending on INCREASING SIGNAL INCREASING SIGNAL
—
diameter of conductor, and depth. NO SIGNAL - NULL

Z’,J? -Z’
\
With the disc held flat, close to the ground, with
1 the bubble centered, the conductor lies directly
below the center of the disc. This null is very ///////////// /1////[/////
accurate. However another metallic structure close by
may disturb it to some extent.
Usual practice is to use the maximum position 4 FIG. 2

Pege 5

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for general quick tracing and the NULL position for Section 5
pin pointing the location. ESTABLISHING THE SIGNAL CURRENT CIRCUIT
4.3 DEPTH DETERMINATION
When an exact null (4.2) is obtained, the The signal current is established by a number of
position of the center of the disc is marked on the methods, depending upon the circumstance. The objective is
to establish a series loop circuit between the output binding
ground surface. The disc is then tipped to 45 degrees
posts which will include the conductor as a part. The signal
(bubble touching the outer edge of the ring on the current travels through metallic conductors just as any other
level). The disc is then moved horizontally sideways current would. Its nature is such that it will pass through the
from the mark until another NULL is obtained. The soil surrounding the conductor. It will also pass through the
distance moved is equal to the depth of the con- electrical capacitance between the conductor and its sur-
ductor below the first NULL. (Figure 3) roundings. All these paths are taken advantage of in setting up
the circuit.
a. When two points on the conductor are available some
distance apart and the path between them is to be traced, one
output binding post is connected to one point on the
conductor. An insulated wire is run from the other binding
& ‘%T:” 4 post to the second point on the conductor. The wire should be
COIL LEVEL COIL AT 45° kept about 50 feet away from the probable path of the
conductor to minimize the signal from the wire. The low
y’>
450 impedance switch position will probably be best in this
c #
I situation. Be sure that all connections are tight. (Figure 4)
/1//////// / / / Y / / / / / / l / / / / / /
b. When one point on a conductor is available and there
is within reaching distance a metallic structure which may be
/
used as a ground connection, connect the point on the
DEPTH
I / conductor to one output binding post, and the other to the
grounding structure. The loop circuit is then closed between
FIG. 3 them by soil conductance and capacitance. The signal will be
heard in both the conductor and the grounding structure. The
best impedance will be found by trial. (Figure 5)
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Examples of grounding structures are:

-— —— .
Water systems u CONDUCTOR
— — Ti
Gas systems -
b oo~b~
Steel building frames
T
Power circuit ground wires or conduits A;~TT
Manhole and drain covers
Valve boxes
Chain fencing and metal fence posts
t
Metal traffic signs FIG 4
Metal road guard rails !

c. When one point of the conductor is available and no

convenient ground is nearby, a metal rod may be driven for a SIGNAL IN BOTTRECTIONS I
— —
:Nocn
—
ground approximately 50 feet or so away from the probable L —— — — ——
path of the conductor and the connection completed as in b.
In many cases a good signal is obtained with a rod about 18
GROUNDED
inches long pushed by hand into a moist soil. If a high STRUCTURE
resistance soil condition is found, a longer rod should be
ii
driven several feet into the ground. Water poured around the ~

rod will also help. (Figure 6)

On a pipe protected with buried anodes, the connection
to the anode may be opened and the anode used as a ground. SIGNAL IN ~T14 DIRECTIQJS
— —
x0um6ir
c————.—_=—

ORWEN
GROUND

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Section 6 If open, a traverse around the point of loss will not

OPERATING NOTES reveal any signal in another direction. However
another strong signal in another direction indicates a
6.1 The distance a signal will carry depends upon a bend. If the second signal widens out and becomes
number of conditions. If the conductor is a well “mushy”, the probability is that a ground exists at
coated pipe, it is not uncommon to follow the signal that point due to signal current leaving the cable and
for several miles in each direction from the point of spreading out in the soil. (Figure 7)
connection. If this point is made near one terminus of 6.3 A pipe or cable may be traced at a river crossing
the line, all the signal goes in one direction, and a by connecting the transmitter near the bank and
greater distance is achieved. following the signal out into the river in a boat. Two
On a bare line the signal can be expected to stations on shore, equipped to take bearings on the
carry several hundred feet. On pipe networks the boat on signal, will enable the course of the con-
distance will also depend on the number of branches ductor to be plotted.
which absorb signal. 6.4 BENDS AND STUB ENDS: When the signal fades
Insulated joints cause a sharp drop in signal as out on a pipe run, it may mean a stub end or change
they are passed. This is used as an indication of in direction. Sweeping a traverse around the point of
insulator condition. If the insulators can be shorted signal loss may reveal one or two signal paths in
out as they are reached in succession, the line can be another direction, indicating an elbow or T connec-
surveyed without moving the transmitter, and the tion. (Figure 8)
shorts removed on retrace. 6.5 BRANCH TAPS AND FOREIGN CONTACTS:
The depth at which a conductor can be effec- Branch taps such as water or gas services off a main
tively located depends largely on the strength of the can be found by walking to one side of the main,
signal current. Particular attention should be given to holding the antenna as in Figure 1 B. Very little signal
transmitter connections. Depths of 20 to 30 feet are will be heard from the main, but each tap will
possible. produce a signal as it is reached. (Figure 9)
6.2 When tracing a buried cable, a sudden loss of In the same manner, a strange signal where none
sigilal along the path means either an open or ground. should exist would indicate a contact with a foreign

Paga 8

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conductor which is taking off signal current.

6.6 BUILDING ELECTRIC CIRCUITS AND
PIP I NG: Active power cables may be traced with the
receiver only. The power hum and appliance noise qGNhL
GONE
acts just the same as signal current. TEE
Wiring conduits may be traced by setting up a :L!
FIG. 8
loop circuit such as in Figure 4, connecting the far
end of the conduit to a water or gas line to complete
the loop back to the transmitter.
Conductors buried in concrete floor slabs will
usually respond to the ground return circuit of Figure
5, using a ground connection to the building frame.

GROUND
CONN&CTION
GROUND
CONNECTION
I
I
!

SIGNAL GONE SIGNAL FADEs GOOO SIGNAL

/\
BREAK
OR OPEN -
- 3 0 - 3
FIG. 7

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Section 7 Section 8
BATTERIES AND REPLACEMENT REPLACEABLE PARTS AND REPAIRS
The transmitter operates on a 12 volt battery. The Normally no maintenance except battery replacement
battery connection is made with a short cable and Cinch– is required.
Jones S302CCT or equal connector. The wide blade is positive Repairs are promptly handled at our factory. Return
and the transmitter input is diode protected against accidental the instrument, properly packed, to:
reversal. NILSSON ELECTRICAL LABORATORY, INC.
The battery supplied is a NEDA No. 926, Eveready No. 111 EIGHTH AVENUE
732, or Burgess No. TW2, 12 volt Iatern battery. Two 6 volt NEW YORK, N. Y.1OOI1
batteries, Eveready No. 510S or Burgess F4BP may be used in TELEPHONE: (212) 675-7944
series and will fit the same space. The Nilsson Model 110 Include in the package suitable paper work and instructions.
rechargeable 12 volt battery pack will clamp directly into the
* x
same space.
The battery drain is from 800 to 1000 M. A., depending MODELIIO
upon the transmitter loads. The higher the frequency, the less RECHARGEABLE 12 VOLT BATTERY PACK
drain. will outlast hundreds of 12 volt lantern batteries
The plug in cable allows the use of other batteries such SPECIALLY DESIGNED FOR USE WITH
as a car or truck source. A suitable connector cable is easily NILSSON MODEL 715 PIPE& CABLE LOCATOR
made for this purpose. AND OTHER NILSSON INSTRUMENTS
The receiver is powered by two snap top 9 volt transistor
radio batteries, connected in series for 18 volts. NEDA No. The Model 110 battery pack will
1604, Eveready No. 216, or Burgess 2U6 are suitable. clamp directly in the same space
To change receiver batteries, remove the two screws as the 12 volt lantern battery
located at each end of the name plate strip and one under the normally supplied. It can be
input jack. Slide the chassis out of the phenolic case. Snap one used over a wide operating
battery on each of the polarized snap connectors, making sure temperature range under rugged
field conditions.
the snaps fit properly.
Receiver battery drain is 10 M.A. standby, 12 MA.
RECHARGES OVERNIGHT
when a strong signal is received.
CANNOT BE OVERCHARGED
As with any battery powered device, if the locator is not
to be used for long periods of time, batteries should be Plugs into any ? 10 or 230 volt
removed to rx-event damage from leaking electrolyte. A.C. outlet. It can be recharged
hundreds of times.
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