3M
™
Quick Guide:
20 Steps to Cable Path
Locating Using 3M
™
Dynatel
™
Cable Locators
Transmitter:
577 Hz / 8 kHz (audio) and
33 kHz / 200 kHz (RF) frequencies
1. The Audio trace frequencies (577 Hz / 8 kHz) should be
used whenever possible as first selection. They will travel
further and have less bleed-over of the tracing signal to
adjacent facilities. The RF trace frequencies (33 kHz /
200 kHz) should only be used when the loop (continuity)
resistance is high and prohibits the use of the audio
frequencies. See Step 3 for loop resistance information.
Direct Connect Method
2. Remove bond and direct connect (using Direct Connect
Cable with BLACK and RED Leads) to cable shield
leaving the far end grounded. Place the ground rod 90
°
from suspected cable path and connect the BLACK Lead
to the ground rod and RED Lead to cable shield of the
cable to be located.
3. Power on the Transmitter by pressing the Ohms key
(2nd from left) and check the loop (continuity) resistance
of the trace circuit. This value will be used to select
the “best bet” locating frequency. If ‘OL’ appears in the
display, the trace circuit is open and tracing will be more
difficult. Check the far end ground and lead connections.
Here is a guide to choosing the “best bet” frequency
based on loop resistance: 0-2K ohms select 577 Hz,
3K-6K ohms select 8K, 7-10K ohms select 33K, greater
than 10K ohms select 200K.
4. Press the Trace key on the Transmitter as many times as
necessary to select 577 Hz, 8K, 33K or 200K frequency.
5. If the locate is over 500 feet, or ‘ALL’ Trace frequencies
were selected, press the Output Level key to select high
output power level on the Transmitter. If unsure of which
frequency to use, select ‘ALL’ and try each frequency on the
Receiver for best available selection based on locate signal
response.
Dyna-Coupler Method
6. Couple around the connected cable using the Dyna-Coupler
and coupler cable. Be sure that the coupler is placed between
the shield bonding device and the soil. Far end should be
grounded for best results.
7. Power on the Transmitter and choose 33K, or 200K, and
high output power level. The Dyna-Coupler will not work with
577 Hz.
NOTE: If the cable is not terminated, and the ends are isolated,
you must use the Direct Connect Method in Step 2 and select high
output power level.
Induction Method
8. As a last resort you can use the Induction method by setting
the Transmitter on the ground over the cable with the hinge
in line with the cable. Induce a signal using 33K or 200K and
high output power level. Be sure nothing is plugged into the
Transmitter Output Jack.
Passive Power Method
9. If using 60 Hz selection on receiver, no transmitter is needed;
however, the cable should be energized with sufficient AC
current. Try 60 Hz, then 60H if signal responds slowly or poorly.
60L is the third choice.
Receiver
10. Power On the Receiver, press Locate/OK and choose
Cable/Pipe.
11. Press the Freq key and then the first yellow soft key labeled
Active as many times as necessary to select the same
frequency that was selected on the Transmitter and press
Locate/OK.
12. Press the Mode key as many times as necessary to
select the locate mode (Directional Peak (Dir Pk), Special
Peak (Spl Pk), etc.)
13. Stand away from the suspected target path and adjust
the Gain down until the Bar Graph on the display opens
completely.
14. Walk in a wide circle with your back to the Transmitter
(10-15 ft. away) and the Receiver handle perpendicular
to the Transmitter.
15. Watch the Bar Graph and listen to the audible signal.
Note where the strongest signal is detected. Adjust the
Gain down if the Bar Graph closes completely.
16. Measure the depth and relative current (See
Depth &
Relative Current
section) of each point to identify the
target. The depth should be as expected and the relative
current should compare reasonably close to the relative
current that is alternately flashing with the frequency
value on the Transmitter.
17. Adjust the Gain so that the Bar Graph responds to the
target path (open when off path and almost completely
closed when directly over the target).
18. Trace the cable at a slow walk while moving the
Receiver in a side-to-side motion, keeping the Receiver
perpendicular to the ground.
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