Twinaxial Cai?Le Continuity And Polarity Check - IBM 5280 Technical Newsletter

711
TWINAXIAL CABLE CONTINUITY AND
POLARITY CHECK
Use the continuity and polarity check to test the twinaxial
cable for open and shorted lines and for lines that. have
reversed polarity.
The total length of the cables cannot exceed 1524 meters
(5000 feet). .
To perform the continuity and polarity checks, you need
i:ln ohmmeter to measure resistance and jumpers to
connect the signal lines (connector pins) to the cable
shields (connector body).
Continuity Check
Perform the continuity check as follows:
1.
106
Unplug both ends of the cable. The following
resistance measurements must exceed 100 000
ohms.
a. Phase A to phase B
b. Phase A to shield
c. Phase B to shield
Phase·B·
a
711
2. Connect Phase A and Phase B to the shield at one
end of the cable.
3. Perform the following resistance measurements at
the other end of the cable:
a. Phase A to phase B 110 ohms or less
b. Phase
A
to shield 70 ohms or less
c. Phase B to shield 70 ohms or less
Note: If the preceding checks show that the cable is
open or shorted, see 713 to find the location of the open
or shorted lines.
Polarity Check
Perform the polarity check as follows:
1.
2.
Connect phase A to the shield at one end of the
cable.
Perform the following resistance measurement at
the other end of the cable:
Phase A to shield 70 ohms or less
Note: If the resistance exceeds 70 ohms, the lines are
reversed.