Radiodetection PCMx Guia Del Usuario página 9

To turn the internal GPS on:
1. Press the key to enter the menu.
2. Scroll to the GPS menu using the
or keys.
3. Press the key to enter the GPS
menu.
4. Scroll to INT to select internal GPS.
5. Press the key twice to accept
your selection and return to the main
operation screen.
6. When a GPS lock has been acquired
the GPS lock symbol will display on
the screen. An indicator of the number
of satellites in view is also given.
Conducting an ACCA survey
An Alternating Current, Current
Attenuation, (ACCA) survey measures the
attenuation of the transmitted 4Hz signal
to establish the pattern of current loss.
The results can be used to; establish the
condition of the pipeline coating, locate
faults, or find shorts caused by contact
with other metal objects.
Having used the pinpointing method
above to ensure you are directly above
the correct pipeline, it is now possible to
take measurements of the 4Hz signal.
Procedure:
1. Use the peak response reading and
compass direction to ensure you are
directly above the pipeline.
2. Sit the receiver on the ground,
keeping it upright and very still.
3. Press and hold the key for
approximately one second. Upon
release a live 4Hz reading is
displayed on the bottom right of the
screen. It is normal for this reading
to fluctuate within a couple of mA.
However, a widely fluctuating reading
may indicate interference and it may
be better to move along the pipeline
to take the measurement.
4. The reading can be stored by pressing
the or rejected by pressing the
key. The PCMx can store up to 10,000
readings and the log number of the
stored reading will be shown on the
display.
5. Continue taking readings in this way
along the length of the pipeline you
wish to survey
6. For best results, readings should be
taken at intervals of equal distance.
NOTE: If Bluetooth is switched on, the
PCMx receiver will automatically attempt
to send the reading via Bluetooth to
a paired device. If the PCMx has not
been paired, a BT error code will be
displayed. If it is intended to only save
the reading internally within the PCMx
receiver, switch the BT-PC setting in the
DATA menu to OFF.
Temporary measurements
In some situations, it can be difficult to view
the display when taking a measurement.
A temporary measurement can be taken
for review before committing the record
to memory. Take the measurement as
detailed above, but instead of pressing
the save or delete key, press the antenna
key The measurement will be held
on screen for review. To save the
measurement, press .
Review and Overwrite
Measurement Logs
Saved readings within the PCMx can be
reviewed or overwritten. To view a saved
result, press to enter the system menu
and select VIEW. The last saved result will
be displayed. To view other logs, use the
or keys to step through.
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To overwrite a saved result, select the
result log and press . Once a new
measurement is taken, press the key
to overwrite the selected reading. The
log number that was overwritten will be
displayed and the receiver will revert to
storing new measurements at the end of
the current records.
Conducting an ACVG survey
An Alternating Current Voltage Gradient,
(ACVG), survey measures the leakage
current in the vicinity of the pipeline
to assess the coating condition, and
pinpoint coating defects. An advantage
of this survey method is that it can be
done on a route parallel to the pipe. For
example, it may be done on a pavement
or grass verge parallel to a pipe running
below a road surface. It requires the use
of an A-Frame in addition to the PCMx
receiver and transmitter.
Procedure:
1. Connect the transmitter to the pipeline
and ground using the procedure
described previously.
2. Set the PCMx transmitter to either
ELCD or LFCD mode.
3. Connect the A-frame to the PCMx
receiver via the accessory socket,
and turn on the receiver.
4. The PCMx will automatically choose
ACVG mode and an A-frame symbol
will be displayed.
5. Choose an appropriate starting point
for your survey. If a suspected fault
location has been identified from a
previous ACCA survey, begin the
survey approximately 60 feet, (20
meters) from the suspected fault.
6. Place the A-frame spikes in the
ground above, or parallel with,
the pipe. Position the green spike
forwards and the red spike towards
the transmitter connection point.
7. If no fault is apparent, the arrows
will flicker on and off and the dB
readings will be erratic. When a fault
is present, the Fault Find, (FF) arrows
will display the fault direction and the
dB readings will be stable. The dB
reading will increase as the A-Frame
is positioned closer to the fault.
8. Follow the pipeline pushing the
A-Frame spikes into the ground at
regular intervals and checking for
FF arrows.
9. Move in the direction of the arrows.
Find the point at which the arrows
change direction. If the A-frame has
been positioned directly above the
pipe, the fault location will be directly
below the A-Frame at this point.
10. If the measurements have been taken
to the side of the pipe line, rotate the
A-Frame 90° so that the green spike
points towards the pipeline. Move
back and forth across the pipeline to
locate the fault in this direction, the
intersection point will be directly over
the fault.
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