Edgetech 4200 User Hardware Manual page 104

Shorted Wire
The following procedure may be used to approximate the distance to a single short or a point of high
leakage between a conductor pair or from a conductor to a shield.
1. Disconnect both cable ends.
2. Short the two connector pins (or wires if un-terminated) of the shorted pair at both ends and
measure the total resistance between the ends.
R1+R2 =_______________
3. Remove the shorts.
4. Measure the resistance between a shorted pair on one end with an ohmmeter on the Rx1 scale.
R1+Rs =_______________
5. Measure the resistance from the other end.
R2+Rs =_______________
6. Add the measurements of 4) and 5) above, subtract the measurement of 2), and divide the result
by 2.
Rs =_________________
7. Subtract the value of 6) from the measured values of 4) and 5).
R1 =_________________
R2 =_________________
8. The distance to the short from end #1 is the ratio of (R1/R1+R2) times the total cable length.
Recheck from end #2 that is (R2/R1+R2) times the cable length.
Open Wire
An open wire in a cable is much more difficult to locate than a short circuit. Therefore, a capacitance
bridge is recommended. Measuring the capacitance from the open wire to the shield on both ends allows
two different capacitance readings to be recorded. This represents a direct ratio related to cable length
and distance of break from each end. Before cutting the cable, double-check the same ratio of capacitance
using an adjacent good wire in a multi-conductor cable. The capacitance may vary from wire to wire,
depending on their separation.
Most breaks occur around the tow cable termination or where a previous repair has been made. A cable
break may be found or confirmed by laying out the cable and attaching an ohmmeter across each end of
the open wire. Then, flex the cable first near the termination or repaired section, and then along its entire
length until the break is reached. When flexing, the ends of the broken wire may touch, giving a continuity
reading on the meter.
4200 SIDE SCAN SONAR SYSTEM USER HARDWARE MANUAL
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