July 09, 2023
For those who are new to security industry, there is a lot of knowledge to learn. In actual engineering and maintenance and overhaul, beginners are even more afraid of suddenly encountering problem “the wire and cable are broken, but they cannot find place of break.”
Today I would like to share experience of a 20-year-old electrician with newbies in security, and see how an old electrician determines location of wire and cable breaks in real operation.Inductive pen detection
An inductive electric pen is an electronic screen device that can detect voltage and turn on/off. First rule out that cables around breakpoint cable have power, then connect cable with breakpoint to live wire, put electric pen perpendicular to wire, press and hold "Inductive Breakpoint Test" button, and slowly move forward. wire and wait for test pen to detect. When AC signal suddenly disappears, it can be concluded that breakpoint is at detection point, and error is no more than 10cm.
Note: The cables around break point wires cannot be powered. In addition, effect of short cables is obvious, while effect of long cables is worse.Multimeter test
Connect one end of any unconnected cable to a energized high current line, and leave other end blank. Turn multimeter to AC2V range, start at power terminal of cable, hold tip of black pen and slowly move red pen along insulation of wire. At this time, display shows a voltage of about 0.445 V.
When red test pen is moved to a specific location, voltage shown on display suddenly drops to 0.0V, which is about one tenth of original voltage. Where is breakpoint.Audio detector
An audio detector is a device that uses single-frequency or multi-frequency signals to check continuity of a line in order to detect line problems. It can directly find line when connected to any switch, router or computer terminal. When tracing a cable line, there is no need to peel off line sheath, which is done simply and quickly and allows you to determine position of the line break point.Cable Fault Tester
It can test high resistance cable overlap, high-low resistance ground, short circuit, cable disconnection, poor contact and other faults. If it is equipped with an acoustic measuring instrument, it can accurately determine exact location of fault. It is particularly suitable for testing power and communication cables of various types and voltage levels.Acupuncture test
This method belongs to fault detection method. Insert steel needles into segments on broken cable and use a multimeter to measure continuity of steel needle to end of cable to determine break point of cable.Break line detection method
Connect one end of wire with break point to black probe of multimeter and other end to red probe. The multimeter is in a 200 ohm resistance file. Bend back and forth where wire is most likely to break, such as where it often bends. If multimeter shows it suddenly turns on and off, it's a breakpoint. If you still can't tell, you'll need to bend at one end of cable until you find break point. This method is suitable for shorter cables.Trailing Wire Detection Method
Use a vise to pull out broken wire at end of cable. If breaking point is near end of cable, insulation breaks easily. This method is used for cables with break points near ends of cable.
To find wire and cable break point, you can refer to 7 methods above. Of course, it's faster to use a discovery tool when conditions permit. As long as we learn more, see more, and ask more questions, sooner or later Xiaobai will counterattack and become a master of security.