Intermittent Faults on ship electrical system
When ships Electrical Engineer ETO need find and diagnose intermittent faults, where a short, open, or other problem occurs only temporarily, or only under certain conditions, is always a difficult troubleshooting problem. Two features found on most DMMs can help with identifying intermittent faults.
Continuity capture mode
This feature is useful for finding intermittent connections with small gauge wires and wiring bundles, and even intermittent ships relay contact. To check for intermittent opens, place the leads across the normally closed
or shorted connection and select Continuity Capture mode on the DMM. Wiggle the wire(s) and heat the connection with a heat gun, or cool it with circuit cooler to make the intermittent open appear. When the open is captured (as short as 250 μs), the display shows a transition from open to a short.
Intermittent shorts can be found the same way, by connecting to a normally open circuit and using the wiggling and heating/cooling techniques to capture the short. The only difference is that the transition
lines will go from the bottom of the display to the top.
Sometimes intermittent faults cannot be successfully induced while observing the DMM display. Some higher-end units have a recording mode with a date and time stamp. This type of DMM can be left connected to a circuit or piece of electrical equipment for an extended period of time to record the occurrence of an intermittent fault. The date and time of occurrence may provide clues that allow the electrician or technician to trace the cause of the fault.