By William Hirsch, Updated Mar 24, 2022
Detecting a short on a printed circuit board (PCB) is essential to prevent accidental shock, equipment failure, and potential fire hazards. A short circuit occurs when the intended path of electrical current is interrupted, causing power to flow through an unintended route. Identifying and correcting these faults can save you from costly replacements and downtime.
A short can happen at the component level—resistors, capacitors, or other devices may become damaged and fail to limit or store current. Because current flow follows Ohm’s law (I = V / R), any sudden reduction in resistance leads to a surge that can damage the entire board.
Press the “Power” button on your digital multimeter (DMM) to turn it on.
Rotate the measurement dial to the DC current mode, indicated by a capital “A” with straight lines over it. The “A” represents amperes, the unit of electrical current.
Using the red (positive) and black (negative) probes, touch the two sides of each component on the PCB one at a time. A reading of zero amperes indicates a short circuit at that component.
Place the probes on opposite ends of each wire connecting components. A zero‑ampere reading again signals a short along that trace.
By systematically applying these steps, you can pinpoint shorts quickly and decide whether to repair the board or replace the entire device.
