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Sensing Cable Test Procedure
Method with TraceTek Portable Test Box (PTB)
1. Ensure the end termination is connected to the sensing cable.
If checking several lengths of sensing cable in series (a cable
string), ensure they are all connected.
2. Connect the PTB to the sensing cable(s) using its adapter,
as illustrated.
3. Verify that the sensing cable is intact; follow the operating
instructions printed inside the lid of the PTB itself. If the cable
string is intact, the PTB measures the system length (length
of TraceTek sensing cable plus the length equivalents of the
weighted lengths and modular branching connectors). If a cable
or connection is broken, the PTB illuminates its LED indicating
"cable break," and displays a "1" in the leftmost position of its
LCD display.
If the cable string is not intact, apply this test procedure to
segments of the system to identify the open connection or
damaged modular length.
Note: If a heat-shrink tube must be removed to access a connector,
refer to Oversleeve Removal Instructions (H54258).
4. Check the condition of the sensing cable(s), again following the
PTB operating instructions. If the sensing cables are clean and
free of contamination, the current measured should be below
10 µA. If the reading exceeds 10 µA, use the PTB to locate the
liquid or contamination and take appropriate corrective action.
Method with Ohmmeter
1. Ensure the end termination is connected to the sensing cable.
If checking several lengths of sensing cable in series (a cable
string), ensure they are all connected.
2. Connect a Modular Leader Cable (TT-MLC-MC) to the
sensing cable.
3. Verify that the sensing cable is intact
• Loop 1: Measure the resistance
between the yellow and black
wires of the leader cable
as illustrated.
• Loop 2: Measure the resistance
between the red and green wires
of the leader cable.
The readings should roughly equal a
multiple of the length of sensing cable:
4 times the length of sensing cable (in ft) or
12 times the length of sensing cable (in m)
Example:
4 x 50 ft of cable
12 x 15 m of cable
In addition, the resistance of the two loops should be within
5 percent of each other.
If the cable string is not intact, apply this test procedure to
segments of the system to identify the open connection or
damaged modular length.
Note: If a heat-shrink tube must be removed to access a
connector, refer to Oversleeve Removal Instructions (H54258).
4. Check the condition of the sensing cable. Measure the
resistance between the black and green wires of the leader cable.
• If the reading is below 20 MΩ, apply this test procedure to
segments of the system to identify the modular sensing cable
length(s) affected, locate the liquid or contamination, and take
appropriate corrective action.
To yellow
To black
To red
To green
= 200 W,
= 180 W.
Testing a string of cables
End termination
PTB
Testing an individual length of cable
End termination
Testing a string of cables
End termination
Ohm
meter
TT-MLC-PC
Testing an individual length of cable
End termination
End
termination
End
termination
nVent.com | 5
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