3M CablePipe Locating Techniques Manual

11
B Power Frequencies
5.4 An energized cable carrying AC power produces a 50 or 60 Hz signal. Although these are
relatively low frequencies, they can still couple into other conductors buried nearby. You can
detect the conductor because of the signal, but identification is impossible. The signal could be
coming from a power cable, a nearby pipe, or concrete reinforcing bars. However, the knowledge
that these conductors exist is useful.
5.5 Most energized power cables are easy to detect but sometimes...

12
6. Choosing Trace Modes
6.1 In most cases, you would choose PEAK mode, but for fast or difficult tracing other modes can be
handy. The following is a brief description of each trace mode:
 PEAK: In this mode, the Receiver speaker volume increases to a maximum as the
antenna crosses the cable.  It diminishes as the antenna moves away from the cable
path.  Simultaneously, the bar graph fills from both sides toward the middle as the
peakÕ zone is crossed then opens as the midpoint is passed.  The numeric...

13
7. One Touch Gain Adjust
7.1ItÕs SimpleÉ No GuessingÉ No Trial & Error... No multiple presses neededÉ When using Peak
or Null Tracing modes, just press the Receiver Gain-key ÒonceÓ to automatically adjust the gain
and set the bar graph reference point.
7.2Always adjust the Receiver gain only when you are over the target cable and in either Peak or
Null mode. If too much signal is indicated by a completely closed bar graph, press the Gain Adjust
key once to automatically adjust the gain and set the bar...

14
8. Locating Techniques
A. Sweeping
8.1 Sweeping an area allows you to locate all buried
cable in the area.  Use the Induction method to apply
the Transmitter signal.  Use the highest frequency
available so that all cables in the area carry signal.
Walk in a grid pattern over the area as shown, and
cover the area from two directions. Walk the grid
again using the Power mode.  Stop the sweep when
there is a response.  Locate the position of the cable
then trace it until you are out of the area, marking...

15
D. Identifying a Cable by Depth-Current Measurement
8.6 When you apply signal to a cable (using the direct-connect or Dyna-Coupler methods) the signal
can travel on all the cables which share ground with your target cable. This can cause trouble with
the locate, as a shallow cable with a weak signal can give as good a response as a deep cable with
a strong signal.
8.7 In the illustration below, transmitter signal was applied to cable B and a strong signal current
travels its length.  Cable A shares...

16
8.8 Imagine this problem: You know you have two cables with the same signal and just when you
think youÕve got the target cable identified, the two cables cross. Again, you can use the depth-
current measurement to identify the target cable. When cables A and B cross, they change depth.
This is not unusual and is often the case.  Since the ReceiverÕs signal response varies with depth, it
may be difficult to identify the cables using signal level alone.  However, the signal current in the
cables will...

17
9. External DC Power and 5 Watt Output
A External DC Power
9.1 Dynatel Transmitters with option A can be operated from an external 12VDC source as well as its
internal batteries. A cigarette lighter adapter-cable is supplied to connect the DC power from a
vehicleÕs battery to the Transmitter Õs external power connector located next to the output
connector. This lets you save the internal batteries by using an external power source or continue
operating when the internal batteries are discharged. The...

18 

19
Section 2 Telephone Cable Locating Techniques
1. Introduction
1.1 Read Section One of this manual to learn more general information about each of the following
signal application methods. The following paragraphs provide specific instruction on applying
signal for telephone cable locating.
2. Applying Signal to Telephone Cable: Induction Method
2.1 The Induction method broadcasts signal into an area. No access to the cable is necessary. Use this
only when there are no other buried conductors present,...

20
3. Applying Signal to Telephone Cable: Direct Connect Method
3.1 The direct-connect method requires access to the cable shield.  Disconnect the cable at the near-
end where the Transmitter is connected. Do not disconnect at the far-end since this supplies a far-
end ground.
3.2 Connect the red lead of the Transmitter to the cable shield and the black lead to the ground rod.
Warning! Potential for electrical shock exists when handling connecting cables while the Transmitter is in the
Fault or Tone...