Planning the cable path
OmniTrax Product Guide Page 49
Metal objects or obstructions
Metal objects located near the sensor cables can distort the detection field, causing uneven
sensitivity (see Separation distances from obstacles
on page 42). Differences in soil composition
make it difficult to predict the exact effect at a particular site. If there are metal objects near the
cable route that cannot be removed, mark the location along with a detailed description on the site
survey. This information can be useful during the calibration process. Some of the potential
problems arising from metal objects include:
• intermittent electrical contacts
• detection field containment (redirection of the detection field)
• variations in detection sensitivity
Use the following guidelines to assist in planning for and overcoming the effects of metal objects.
Pipes, conduits, and electrical cables
If a pipe, conduit, or electrical cable is buried near the cable path, it may have an affect on the
system (see Separation distances from pipes, conduits and cables
on page 42). To be assured of
trouble-free operation objects should be separated from the sensor cables by the distances listed
in the separation table. The separation distances indicated are minimum requirements. If more
space is available, increase the separation distance. Non-metal pipes or conduit that are shielded
or wrapped with foil are equivalent to metal pipes or conduit.
Metal pipes crossing the sensor cable path should not have any joints or breaks. Check that the
pipe has no loose fittings. If a pipe is no longer in use, it is recommended that it be removed from
the zone.
Drainage culverts
Culverts or pipes buried 1 m (3.3 ft.) or more below the surface should not cause any problems
(see Installation near drainage culverts
on page 43). Pipes less than 1 m below the surface should
be of metal construction, to reduce the potential for nuisance alarms from water flowing in the pipe.
Metal culverts must be of continuous construction where they cross the sensor cables to avoid
intermittent electrical contacts. Shallow buried pipes made of concrete or plastic can be covered
with a metal shield or metal foil in the vicinity of the sensor cables. Use foil that is designed for
direct burial to ensure that it won’t degrade in the soil. The pipe can then be treated as a metal
pipe, and the separation distances for metal pipes apply. The shield or foil will reduce the potential
for nuisance alarms that can occur from water flow in the pipe.
Water
Water that accumulates in puddles (standing water), ditches, or water flowing through
underground, non-metal pipes can cause nuisance alarms (see Separation distances from
obstacles on page 42). Ensure that there is adequate drainage around the perimeter and that
water does not accumulate on, or near, the proposed cable path. If the local climate includes a
rainy season, check with local authorities to determine the effects of heavy rainfall on the site
surface.
Note If replacing an older buried cable system, the old cables should be
removed. If this is not possible, the new cable must have a minimum
separation distance of 3 m (10 ft.) from the old cable.
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