Method for Locating Cable Breakpoints with a Digital Multimeter
Besides measuring basic parameters such as voltage, current, resistance, capacitance and transistor characteristics, a digital multimeter can be used in flexible ways to expand its functions and realize multi‑purpose measurement. The following describes the method for locating breakpoints in wires and cables with a digital multimeter.
When an internal wire break occurs inside a cable, the exact position of the break is hard to identify due to the outer insulating sheath. A digital multimeter can solve this problem conveniently. The specific procedure is as follows: Connect one end of the broken wire (cable) to the 220 V AC live wire, and leave the other end unconnected. Set the digital multimeter to the AC 2 V range. Starting from the live‑wire connection end of the wire (cable), hold the tip of the black probe with one hand, and slide the red probe slowly along the insulating sheath. The displayed voltage reading will be approximately 0.445 V (measured by DT890D multimeter). When the red probe moves to a certain position, the displayed voltage drops abruptly to a few tenths of a volt (roughly one‑tenth of the original value). The breakpoint of the wire (cable) is located about 15 cm toward the live‑wire connection end from this spot.
This method does not work for shielded cables if only the inner conductor is broken while the shielding layer remains intact.
Digital Multimeter
Ⅰ. Overview of Digital Multimeter
This is a compact 3‑1/2‑digit LCD digital multimeter. It can measure AC/DC voltage, AC/DC current, resistance, capacitance, transistor β‑value, diode forward voltage and circuit continuity. A rotary range switch selects measurement functions and ranges, offering a total of 30 ranges.
The maximum display value of this multimeter is ±1999. It can automatically show zero and polarity. "1" or "‑1" appears on the display under overload conditions. A "←" symbol indicates low‑battery voltage, and a buzzer is equipped for continuity check.
