SENSTAR OmniTrax - Ground Faults; Decoupler Faults; Testing for Faults (Required Equipment); Cable Damage

Repairing sensor cables
OmniTrax Product Guide Page 155
Ground faults
A ground fault occurs when the cable’s outer protective jacket is damaged, creating a path
between the conductive material in the cable and the ground. Ground faults can be intermittent,
often depending on the soil’s electrical properties and level of moisture. This kind of cable damage
must be repaired promptly. If not, the problem will become worse over time as moisture penetrates
and corrodes the sensor cable. Even minor cable damage can have a negative effect on system
performance.
Decoupler faults
If decouplers are not sealed correctly, water can enter the decouplers, connectors and possibly the
sensor cable. This will result in ground faults as a conductive path is created between the
decoupler/sensor cable and the ground.
Testing for faults (Required equipment)
• PC running UCM software and USB cable
•multimeter
• cable ground fault locator (optional)
Test sequence
• connect the processor to a computer running the UCM software
• observe the clutter display from the suspect cable set
• locate the ground fault (cable damage) by noting the position of the excessive clutter
Additional tests
(see Cable tests on page 146)
• perform a leakage resistance test to determine which cable is damaged
• perform an insulation resistance test to determine if severe cable damage is present, or if the
decoupler is faulty
• if required, use a cable ground fault locator to determine the location of the cable damage
Decouplers
If a decoupler is suspected of causing the ground fault, expose the decoupler and isolate it from
the ground. Perform a leakage resistance test to see if the ground fault disappears when the
decoupler is isolated from the ground. If the ground fault is still present when the decoupler is
isolated from the ground, it is not the source of the problem. If the ground fault is gone, replace the
decoupler.
Cable damage
If the sensor cable is the source of the ground fault, you must locate the cable damage. If recent
construction or landscaping work has been done close to the cable path, the cable damage will
most likely be located there.
• use the UCM software to identify the location of cable damage
• use a cable ground fault locator to determine the location of cable damage
• carefully dig up the cables in the suspect location, inspect the cable and assess the level of
damage